Merge branch 'develop'

2021-06-10 19:38:23 +09:00 · 2021-06-10 19:38:23 +09:00 · c8ab244ae9
commit c8ab244ae9
parent f0b87f39c3 a1ffe0a776
284 changed files with 4681 additions and 4008 deletions
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@ -14,8 +14,8 @@ jobs:
    steps:
      - uses: subosito/flutter-action@v1
        with:
-          channel: beta
-          flutter-version: '2.2.0-10.1.pre'
+          channel: stable
+          flutter-version: '2.2.1'

      - name: Clone the repository.
        uses: actions/checkout@v2
@ -31,4 +31,4 @@ jobs:
        run: flutter analyze

      - name: Unit tests.
-        run: flutter test
+        run: flutter test --no-sound-null-safety
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@ -16,8 +16,8 @@ jobs:

      - uses: subosito/flutter-action@v1
        with:
-          channel: beta
-          flutter-version: '2.2.0-10.1.pre'
+          channel: stable
+          flutter-version: '2.2.1'

      # Workaround for this Android Gradle Plugin issue (supposedly fixed in AGP 4.1):
      # https://issuetracker.google.com/issues/144111441
@ -38,7 +38,7 @@ jobs:
        run: flutter analyze

      - name: Unit tests.
-        run: flutter test
+        run: flutter test --no-sound-null-safety

      - name: Build signed artifacts.
        # `KEY_JKS` should contain the result of:
@ -50,8 +50,8 @@ jobs:
          echo "${{ secrets.KEY_JKS }}" > release.keystore.asc
          gpg -d --passphrase "${{ secrets.KEY_JKS_PASSPHRASE }}" --batch release.keystore.asc > $AVES_STORE_FILE
          rm release.keystore.asc
-          flutter build apk --bundle-sksl-path shaders_2.2.0-10.1.pre.sksl.json
-          flutter build appbundle --bundle-sksl-path shaders_2.2.0-10.1.pre.sksl.json
+          flutter build apk --bundle-sksl-path shaders_2.2.1.sksl.json
+          flutter build appbundle --bundle-sksl-path shaders_2.2.1.sksl.json
          rm $AVES_STORE_FILE
        env:
          AVES_STORE_FILE: ${{ github.workspace }}/key.jks
--- a/.gitignore
+++ b/.gitignore
@ -40,5 +40,7 @@ app.*.symbols
 # Obfuscation related
 app.*.map.json

-# Exceptions to above rules.
-!/packages/flutter_tools/test/data/dart_dependencies_test/**/.packages
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@ -3,6 +3,26 @@ All notable changes to this project will be documented in this file.

 ## [Unreleased]

+## [v1.4.2] - 2021-06-10
+### Added
+- Collection: snack bar action to show moved/copied/exported entries
+- Collection / Albums / Countries / Tags: when switching device orientation, keep items in view
+- Collection: when leaving entry from Viewer, make entry visible in collection
+- Viewer: fixed layout & minimap for videos with non-square pixels
+
+### Changed
+- upgraded Flutter to stable v2.2.1
+- migrated to unsound null safety
+- Collection / Viewer: improved performance, memory usage
+- Collection: thumbnail layout change
+
+### Removed
+- no support for Android KitKat (API 19), unsupported by Google Maps package
+
+### Fixed
+- fixed opening files shared via content URI with incorrect MIME type
+- refresh collection when entries modified in Viewer no longer match collection filters
+
 ## [v1.4.1] - 2021-04-29
 ### Added
 - Motion photo support
--- a/README.md
+++ b/README.md
@ -21,7 +21,7 @@ Aves is a gallery and metadata explorer app. It is built for Android, with Flutt
 - search and filter by country, place, XMP tag, type (animated, raster, vector…)
 - favorites
 - statistics
- support Android API 19 ~ 30 (KitKat ~ R)
+- support Android API 20 ~ 30 (Lollipop ~ R)
 - Android integration (app shortcuts, handle view/pick intents)

 ## Known Issues
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@ -29,6 +29,6 @@ linter:
    unnecessary_lambdas: true

    # misc
-    prefer_const_constructors: false # too noisy
+    prefer_const_constructors: true # should specify `const` as Dart does not build constants when using const constructors without it
    prefer_const_constructors_in_immutables: true
    prefer_const_declarations: true
--- a/android/app/build.gradle
+++ b/android/app/build.gradle
@ -53,8 +53,8 @@ android {

    defaultConfig {
        applicationId "deckers.thibault.aves"
-        minSdkVersion 19
-        targetSdkVersion 30 // same as compileSdkVersion
+        minSdkVersion 20
+        targetSdkVersion 30
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
        manifestPlaceholders = [googleApiKey: keystoreProperties['googleApiKey']]
@ -100,16 +100,16 @@ flutter {

 repositories {
    maven { url 'https://jitpack.io' }
-    maven { url "https://s3.amazonaws.com/repo.commonsware.com" }
+    maven { url 'https://s3.amazonaws.com/repo.commonsware.com' }
 }

 dependencies {
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9'
-    implementation 'androidx.core:core-ktx:1.5.0-rc01' // v1.5.0-alpha02+ for ShortcutManagerCompat.setDynamicShortcuts
+    implementation 'androidx.core:core-ktx:1.5.0'
    implementation 'androidx.exifinterface:exifinterface:1.3.2'
-    implementation "androidx.multidex:multidex:2.0.1"
+    implementation 'androidx.multidex:multidex:2.0.1'
    implementation 'com.commonsware.cwac:document:0.4.1'
-    implementation 'com.drewnoakes:metadata-extractor:2.15.0'
+    implementation 'com.drewnoakes:metadata-extractor:2.16.0'
    implementation 'com.github.deckerst:Android-TiffBitmapFactory:876e53870a' // forked, built by JitPack
    implementation 'com.github.bumptech.glide:glide:4.12.0'

--- a/android/app/src/main/kotlin/deckers/thibault/aves/channel/calls/ImageFileHandler.kt
+++ b/android/app/src/main/kotlin/deckers/thibault/aves/channel/calls/ImageFileHandler.kt
@ -29,7 +29,7 @@ class ImageFileHandler(private val activity: Activity) : MethodCallHandler {

    override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
        when (call.method) {
-            "getEntry" -> GlobalScope.launch(Dispatchers.IO) { safesus(call, result, ::getEntry) }
+            "getEntry" -> GlobalScope.launch(Dispatchers.IO) { safe(call, result, ::getEntry) }
            "getThumbnail" -> GlobalScope.launch(Dispatchers.IO) { safesus(call, result, ::getThumbnail) }
            "getRegion" -> GlobalScope.launch(Dispatchers.IO) { safesus(call, result, ::getRegion) }
            "rename" -> GlobalScope.launch(Dispatchers.IO) { safesus(call, result, ::rename) }
@ -40,7 +40,7 @@ class ImageFileHandler(private val activity: Activity) : MethodCallHandler {
        }
    }

-    private suspend fun getEntry(call: MethodCall, result: MethodChannel.Result) {
+    private fun getEntry(call: MethodCall, result: MethodChannel.Result) {
        val mimeType = call.argument<String>("mimeType") // MIME type is optional
        val uri = call.argument<String>("uri")?.let { Uri.parse(it) }
        if (uri == null) {
--- a/android/app/src/main/kotlin/deckers/thibault/aves/metadata/Metadata.kt
+++ b/android/app/src/main/kotlin/deckers/thibault/aves/metadata/Metadata.kt
@ -127,16 +127,7 @@ object Metadata {
                    Log.d(LOG_TAG, "use a preview for uri=$uri mimeType=$mimeType size=$sizeBytes")
                    var previewFile = previewFiles[uri]
                    if (previewFile == null) {
-                        previewFile = File.createTempFile("aves", null, context.cacheDir).apply {
-                            deleteOnExit()
-                            outputStream().use { output ->
-                                StorageUtils.openInputStream(context, uri)?.use { input ->
-                                    val b = ByteArray(previewSize)
-                                    input.read(b, 0, previewSize)
-                                    output.write(b)
-                                }
-                            }
-                        }
+                        previewFile = createPreviewFile(context, uri)
                        previewFiles[uri] = previewFile
                    }
                    Uri.fromFile(previewFile)
@ -147,6 +138,19 @@ object Metadata {
        }
    }

+    fun createPreviewFile(context: Context, uri: Uri): File {
+        return File.createTempFile("aves", null, context.cacheDir).apply {
+            deleteOnExit()
+            outputStream().use { output ->
+                StorageUtils.openInputStream(context, uri)?.use { input ->
+                    val b = ByteArray(previewSize)
+                    input.read(b, 0, previewSize)
+                    output.write(b)
+                }
+            }
+        }
+    }
+
    fun openSafeInputStream(context: Context, uri: Uri, mimeType: String, sizeBytes: Long?): InputStream? {
        val safeUri = getSafeUri(context, uri, mimeType, sizeBytes)
        return StorageUtils.openInputStream(context, safeUri)
--- a/android/app/src/main/kotlin/deckers/thibault/aves/model/provider/ContentImageProvider.kt
+++ b/android/app/src/main/kotlin/deckers/thibault/aves/model/provider/ContentImageProvider.kt
@ -4,10 +4,44 @@ import android.content.Context
 import android.net.Uri
 import android.provider.MediaStore
 import android.provider.OpenableColumns
+import android.util.Log
+import com.drew.imaging.ImageMetadataReader
+import com.drew.metadata.file.FileTypeDirectory
+import deckers.thibault.aves.metadata.Metadata
+import deckers.thibault.aves.metadata.MetadataExtractorHelper.getSafeString
 import deckers.thibault.aves.model.SourceEntry
+import deckers.thibault.aves.utils.LogUtils
+import deckers.thibault.aves.utils.MimeTypes
+import deckers.thibault.aves.utils.StorageUtils

 internal class ContentImageProvider : ImageProvider() {
-    override fun fetchSingle(context: Context, uri: Uri, mimeType: String?, callback: ImageOpCallback) {
+    override fun fetchSingle(context: Context, uri: Uri, sourceMimeType: String?, callback: ImageOpCallback) {
+        // source MIME type may be incorrect, so we get a second opinion if possible
+        var extractorMimeType: String? = null
+        try {
+            val safeUri = Uri.fromFile(Metadata.createPreviewFile(context, uri))
+            StorageUtils.openInputStream(context, safeUri)?.use { input ->
+                val metadata = ImageMetadataReader.readMetadata(input)
+                for (dir in metadata.getDirectoriesOfType(FileTypeDirectory::class.java)) {
+                    // `metadata-extractor` is the most reliable, except for `tiff` (false positives, false negatives)
+                    // cf https://github.com/drewnoakes/metadata-extractor/issues/296
+                    dir.getSafeString(FileTypeDirectory.TAG_DETECTED_FILE_MIME_TYPE) {
+                        if (it != MimeTypes.TIFF) {
+                            extractorMimeType = it
+                            if (extractorMimeType != sourceMimeType) {
+                                Log.d(LOG_TAG, "source MIME type is $sourceMimeType but extracted MIME type is $extractorMimeType for uri=$uri")
+                            }
+                        }
+                    }
+                }
+            }
+        } catch (e: Exception) {
+            Log.w(LOG_TAG, "failed to get MIME type by metadata-extractor for uri=$uri", e)
+        } catch (e: NoClassDefFoundError) {
+            Log.w(LOG_TAG, "failed to get MIME type by metadata-extractor for uri=$uri", e)
+        }
+
+        val mimeType = extractorMimeType ?: sourceMimeType
        if (mimeType == null) {
            callback.onFailure(Exception("MIME type is null for uri=$uri"))
            return
@ -39,6 +73,8 @@ internal class ContentImageProvider : ImageProvider() {
    }

    companion object {
+        private val LOG_TAG = LogUtils.createTag<ContentImageProvider>()
+
        @Suppress("DEPRECATION")
        const val PATH = MediaStore.MediaColumns.DATA

--- a/android/build.gradle
+++ b/android/build.gradle
@ -1,21 +1,15 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 buildscript {
-    ext.kotlin_version = '1.4.32'
+    ext.kotlin_version = '1.5.10'
    repositories {
        google()
        mavenCentral()
-        // TODO TLAD remove jcenter (migrating to mavenCentral) when this is fixed: https://youtrack.jetbrains.com/issue/IDEA-261387
-        jcenter {
-            content {
-                includeModule("org.jetbrains.trove4j", "trove4j")
-            }
-        }
    }
    dependencies {
-        classpath 'com.android.tools.build:gradle:4.1.3'
+        classpath 'com.android.tools.build:gradle:4.2.1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-        classpath 'com.google.gms:google-services:4.3.5'
-        classpath 'com.google.firebase:firebase-crashlytics-gradle:2.5.2'
+        classpath 'com.google.gms:google-services:4.3.8'
+        classpath 'com.google.firebase:firebase-crashlytics-gradle:2.7.0'
    }
 }

@ -23,12 +17,6 @@ allprojects {
    repositories {
        google()
        mavenCentral()
-        // TODO TLAD remove jcenter (migrating to mavenCentral) when this is fixed: https://youtrack.jetbrains.com/issue/IDEA-261387
-        jcenter {
-            content {
-                includeModule("org.jetbrains.trove4j", "trove4j")
-            }
-        }
    }
 //    gradle.projectsEvaluated {
 //        tasks.withType(JavaCompile) {
@ -40,8 +28,6 @@ allprojects {
 rootProject.buildDir = '../build'
 subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
-}
-subprojects {
    project.evaluationDependsOn(':app')
 }

--- a/android/gradle/wrapper/gradle-wrapper.properties
+++ b/android/gradle/wrapper/gradle-wrapper.properties
@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.7.1-all.zip
--- a/lib/geo/countries.dart
+++ b/lib/geo/countries.dart
@ -1,6 +1,7 @@
 import 'dart:async';

 import 'package:aves/geo/topojson.dart';
+import 'package:collection/collection.dart';
 import 'package:country_code/country_code.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
@ -13,17 +14,17 @@ class CountryTopology {

  CountryTopology._private();

-  Topology _topology;
+  Topology? _topology;

-  Future<Topology> getTopology() => _topology != null ? SynchronousFuture(_topology) : rootBundle.loadString(topoJsonAsset).then(TopoJson().parse);
+  Future<Topology?> getTopology() => _topology != null ? SynchronousFuture(_topology) : rootBundle.loadString(topoJsonAsset).then(TopoJson().parse);

  // returns the country containing given coordinates
-  Future<CountryCode> countryCode(LatLng position) async {
+  Future<CountryCode?> countryCode(LatLng position) async {
    return _countryOfNumeric(await numericCode(position));
  }

  // returns the ISO 3166-1 numeric code of the country containing given coordinates
-  Future<int> numericCode(LatLng position) async {
+  Future<int?> numericCode(LatLng position) async {
    final topology = await getTopology();
    if (topology == null) return null;

@ -34,21 +35,25 @@ class CountryTopology {
  // returns a map of the given positions by country
  Future<Map<CountryCode, Set<LatLng>>> countryCodeMap(Set<LatLng> positions) async {
    final numericMap = await numericCodeMap(positions);
-    numericMap.remove(null);
-    final codeMap = numericMap.map((key, value) {
-      final code = _countryOfNumeric(key);
-      return code == null ? null : MapEntry(code, value);
-    });
-    codeMap.remove(null);
-    return codeMap;
+    if (numericMap == null) return {};
+
+    final codeMapEntries = numericMap.entries
+        .map((kv) {
+          final code = _countryOfNumeric(kv.key);
+          return MapEntry(code, kv.value);
+        })
+        .where((kv) => kv.key != null)
+        .cast<MapEntry<CountryCode, Set<LatLng>>>();
+
+    return Map.fromEntries(codeMapEntries);
  }

  // returns a map of the given positions by the ISO 3166-1 numeric code of the country containing them
-  Future<Map<int, Set<LatLng>>> numericCodeMap(Set<LatLng> positions) async {
+  Future<Map<int, Set<LatLng>>?> numericCodeMap(Set<LatLng> positions) async {
    final topology = await getTopology();
    if (topology == null) return null;

-    return compute(_isoNumericCodeMap, _IsoNumericCodeMapData(topology, positions));
+    return compute<_IsoNumericCodeMapData, Map<int, Set<LatLng>>>(_isoNumericCodeMap, _IsoNumericCodeMapData(topology, positions));
  }

  static Future<Map<int, Set<LatLng>>> _isoNumericCodeMap(_IsoNumericCodeMapData data) async {
@ -58,19 +63,21 @@ class CountryTopology {
      final byCode = <int, Set<LatLng>>{};
      for (final position in data.positions) {
        final code = _getNumeric(topology, countries, position);
-        byCode[code] = (byCode[code] ?? {})..add(position);
+        if (code != null) {
+          byCode[code] = (byCode[code] ?? {})..add(position);
+        }
      }
      return byCode;
    } catch (error, stack) {
      // an unhandled error in a spawn isolate would make the app crash
      debugPrint('failed to get country codes with error=$error\n$stack');
    }
-    return null;
+    return {};
  }

-  static int _getNumeric(Topology topology, List<Geometry> mruCountries, LatLng position) {
+  static int? _getNumeric(Topology topology, List<Geometry> mruCountries, LatLng position) {
    final point = [position.longitude, position.latitude];
-    final hit = mruCountries.firstWhere((country) => country.containsPoint(topology, point), orElse: () => null);
+    final hit = mruCountries.firstWhereOrNull((country) => country.containsPoint(topology, point));
    if (hit == null) return null;

    // promote hit countries, assuming given positions are likely to come from the same countries
@ -79,12 +86,12 @@ class CountryTopology {
      mruCountries.insert(0, hit);
    }

-    final idString = (hit.id as String);
+    final idString = (hit.id as String?);
    final code = idString == null ? null : int.tryParse(idString);
    return code;
  }

-  static CountryCode _countryOfNumeric(int numeric) {
+  static CountryCode? _countryOfNumeric(int? numeric) {
    if (numeric == null) return null;
    try {
      return CountryCode.ofNumeric(numeric);
--- a/lib/geo/format.dart
+++ b/lib/geo/format.dart
@ -23,7 +23,6 @@ String _decimal2sexagesimal(final double degDecimal) {

 // returns coordinates formatted as DMS, e.g. ['41° 24′ 12.2″ N', '2° 10′ 26.5″ E']
 List<String> toDMS(LatLng latLng) {
-  if (latLng == null) return [];
  final lat = latLng.latitude;
  final lng = latLng.longitude;
  return [
--- a/lib/geo/topojson.dart
+++ b/lib/geo/topojson.dart
@ -5,11 +5,11 @@ import 'package:flutter/foundation.dart';

 // cf https://github.com/topojson/topojson-specification
 class TopoJson {
-  Future<Topology> parse(String data) async {
-    return compute(_isoParse, data);
+  Future<Topology?> parse(String data) async {
+    return compute<String, Topology?>(_isoParse, data);
  }

-  static Topology _isoParse(String jsonData) {
+  static Topology? _isoParse(String jsonData) {
    try {
      final data = json.decode(jsonData) as Map<String, dynamic>;
      return Topology.parse(data);
@ -23,7 +23,7 @@ class TopoJson {

 enum TopoJsonObjectType { topology, point, multipoint, linestring, multilinestring, polygon, multipolygon, geometrycollection }

-TopoJsonObjectType _parseTopoJsonObjectType(String data) {
+TopoJsonObjectType? _parseTopoJsonObjectType(String? data) {
  switch (data) {
    case 'Topology':
      return TopoJsonObjectType.topology;
@ -46,7 +46,7 @@ TopoJsonObjectType _parseTopoJsonObjectType(String data) {
 }

 class TopologyJsonObject {
-  final List<num> bbox;
+  final List<num>? bbox;

  TopologyJsonObject.parse(Map<String, dynamic> data) : bbox = data.containsKey('bbox') ? (data['bbox'] as List).cast<num>().toList() : null;
 }
@ -54,10 +54,19 @@ class TopologyJsonObject {
 class Topology extends TopologyJsonObject {
  final Map<String, Geometry> objects;
  final List<List<List<num>>> arcs;
-  final Transform transform;
+  final Transform? transform;

  Topology.parse(Map<String, dynamic> data)
-      : objects = (data['objects'] as Map).cast<String, dynamic>().map<String, Geometry>((name, geometry) => MapEntry(name, Geometry.build(geometry))),
+      : objects = Map.fromEntries((data['objects'] as Map)
+            .cast<String, dynamic>()
+            .entries
+            .map((kv) {
+              final name = kv.key;
+              final geometry = Geometry.build(kv.value);
+              return geometry != null ? MapEntry(name, geometry) : null;
+            })
+            .where((kv) => kv != null)
+            .cast<MapEntry<String, Geometry>>()),
        arcs = (data['arcs'] as List).cast<List>().map((arc) => arc.cast<List>().map((position) => position.cast<num>()).toList()).toList(),
        transform = data.containsKey('transform') ? Transform.parse((data['transform'] as Map).cast<String, dynamic>()) : null,
        super.parse(data);
@ -69,8 +78,8 @@ class Topology extends TopologyJsonObject {
      var x = 0, y = 0;
      arc = arc.map((quantized) {
        final absolute = List.of(quantized);
-        absolute[0] = (x += quantized[0]) * transform.scale[0] + transform.translate[0];
-        absolute[1] = (y += quantized[1]) * transform.scale[1] + transform.translate[1];
+        absolute[0] = (x += quantized[0] as int) * transform!.scale[0] + transform!.translate[0];
+        absolute[1] = (y += quantized[1] as int) * transform!.scale[1] + transform!.translate[1];
        return absolute;
      }).toList();
    }
@ -126,17 +135,18 @@ class Transform {

 abstract class Geometry extends TopologyJsonObject {
  final dynamic id;
-  final Map<String, dynamic> properties;
+  final Map<String, dynamic>? properties;

  Geometry.parse(Map<String, dynamic> data)
      : id = data.containsKey('id') ? data['id'] : null,
-        properties = data.containsKey('properties') ? data['properties'] as Map<String, dynamic> : null,
+        properties = data.containsKey('properties') ? data['properties'] as Map<String, dynamic>? : null,
        super.parse(data);

-  static Geometry build(Map<String, dynamic> data) {
-    final type = _parseTopoJsonObjectType(data['type'] as String);
+  static Geometry? build(Map<String, dynamic> data) {
+    final type = _parseTopoJsonObjectType(data['type'] as String?);
    switch (type) {
      case TopoJsonObjectType.topology:
+      case null:
        return null;
      case TopoJsonObjectType.point:
        return Point.parse(data);
@ -153,7 +163,6 @@ abstract class Geometry extends TopologyJsonObject {
      case TopoJsonObjectType.geometrycollection:
        return GeometryCollection.parse(data);
    }
-    return null;
  }

  bool containsPoint(Topology topology, List<num> point) => false;
@ -198,11 +207,11 @@ class Polygon extends Geometry {
      : arcs = (data['arcs'] as List).cast<List>().map((arc) => arc.cast<int>()).toList(),
        super.parse(data);

-  List<List<List<num>>> _rings;
+  List<List<List<num>>>? _rings;

  List<List<List<num>>> rings(Topology topology) {
    _rings ??= topology._decodePolygonArcs(arcs);
-    return _rings;
+    return _rings!;
  }

  @override
@ -218,11 +227,11 @@ class MultiPolygon extends Geometry {
      : arcs = (data['arcs'] as List).cast<List>().map((polygon) => polygon.cast<List>().map((arc) => arc.cast<int>()).toList()).toList(),
        super.parse(data);

-  List<List<List<List<num>>>> _polygons;
+  List<List<List<List<num>>>>? _polygons;

  List<List<List<List<num>>>> polygons(Topology topology) {
    _polygons ??= topology._decodeMultiPolygonArcs(arcs);
-    return _polygons;
+    return _polygons!;
  }

  @override
@ -235,7 +244,7 @@ class GeometryCollection extends Geometry {
  final List<Geometry> geometries;

  GeometryCollection.parse(Map<String, dynamic> data)
-      : geometries = (data['geometries'] as List).cast<Map<String, dynamic>>().map(Geometry.build).toList(),
+      : geometries = (data['geometries'] as List).cast<Map<String, dynamic>>().map(Geometry.build).where((geometry) => geometry != null).cast<Geometry>().toList(),
        super.parse(data);

  @override
--- a/lib/image_providers/app_icon_image_provider.dart
+++ b/lib/image_providers/app_icon_image_provider.dart
@ -6,11 +6,10 @@ import 'package:flutter/widgets.dart';

 class AppIconImage extends ImageProvider<AppIconImageKey> {
  const AppIconImage({
-    @required this.packageName,
-    @required this.size,
+    required this.packageName,
+    required this.size,
    this.scale = 1.0,
-  })  : assert(packageName != null),
-        assert(scale != null);
+  });

  final String packageName;
  final double size;
@ -39,7 +38,7 @@ class AppIconImage extends ImageProvider<AppIconImageKey> {
  Future<ui.Codec> _loadAsync(AppIconImageKey key, DecoderCallback decode) async {
    try {
      final bytes = await AndroidAppService.getAppIcon(key.packageName, key.size);
-      if (bytes == null) {
+      if (bytes.isEmpty) {
        throw StateError('$packageName app icon loading failed');
      }
      return await decode(bytes);
@ -56,9 +55,9 @@ class AppIconImageKey {
  final double scale;

  const AppIconImageKey({
-    @required this.packageName,
-    @required this.size,
-    this.scale,
+    required this.packageName,
+    required this.size,
+    this.scale = 1.0,
  });

  @override
--- a/lib/image_providers/region_provider.dart
+++ b/lib/image_providers/region_provider.dart
@ -9,7 +9,7 @@ import 'package:flutter/widgets.dart';
 class RegionProvider extends ImageProvider<RegionProviderKey> {
  final RegionProviderKey key;

-  RegionProvider(this.key) : assert(key != null);
+  RegionProvider(this.key);

  @override
  Future<RegionProviderKey> obtainKey(ImageConfiguration configuration) {
@ -43,7 +43,7 @@ class RegionProvider extends ImageProvider<RegionProviderKey> {
        pageId: pageId,
        taskKey: key,
      );
-      if (bytes == null) {
+      if (bytes.isEmpty) {
        throw StateError('$uri ($mimeType) region loading failed');
      }
      return await decode(bytes);
@ -66,30 +66,24 @@ class RegionProviderKey {
  // do not store the entry as it is, because the key should be constant
  // but the entry attributes may change over time
  final String uri, mimeType;
-  final int pageId, rotationDegrees, sampleSize;
+  final int? pageId;
+  final int rotationDegrees, sampleSize;
  final bool isFlipped;
  final Rectangle<int> region;
  final Size imageSize;
  final double scale;

  const RegionProviderKey({
-    @required this.uri,
-    @required this.mimeType,
-    @required this.pageId,
-    @required this.rotationDegrees,
-    @required this.isFlipped,
-    @required this.sampleSize,
-    @required this.region,
-    @required this.imageSize,
+    required this.uri,
+    required this.mimeType,
+    required this.pageId,
+    required this.rotationDegrees,
+    required this.isFlipped,
+    required this.sampleSize,
+    required this.region,
+    required this.imageSize,
    this.scale = 1.0,
-  })  : assert(uri != null),
-        assert(mimeType != null),
-        assert(rotationDegrees != null),
-        assert(isFlipped != null),
-        assert(sampleSize != null),
-        assert(region != null),
-        assert(imageSize != null),
-        assert(scale != null);
+  });

  @override
  bool operator ==(Object other) {
--- a/lib/image_providers/thumbnail_provider.dart
+++ b/lib/image_providers/thumbnail_provider.dart
@ -7,7 +7,7 @@ import 'package:flutter/widgets.dart';
 class ThumbnailProvider extends ImageProvider<ThumbnailProviderKey> {
  final ThumbnailProviderKey key;

-  ThumbnailProvider(this.key) : assert(key != null);
+  ThumbnailProvider(this.key);

  @override
  Future<ThumbnailProviderKey> obtainKey(ImageConfiguration configuration) {
@ -22,6 +22,7 @@ class ThumbnailProvider extends ImageProvider<ThumbnailProviderKey> {
    return MultiFrameImageStreamCompleter(
      codec: _loadAsync(key, decode),
      scale: 1.0,
+      debugLabel: kReleaseMode ? null : [key.uri, key.extent].join('-'),
      informationCollector: () sync* {
        yield ErrorDescription('uri=${key.uri}, pageId=${key.pageId}, mimeType=${key.mimeType}, extent=${key.extent}');
      },
@ -43,7 +44,7 @@ class ThumbnailProvider extends ImageProvider<ThumbnailProviderKey> {
        extent: key.extent,
        taskKey: key,
      );
-      if (bytes == null) {
+      if (bytes.isEmpty) {
        throw StateError('$uri ($mimeType) loading failed');
      }
      return await decode(bytes);
@ -66,25 +67,21 @@ class ThumbnailProviderKey {
  // do not store the entry as it is, because the key should be constant
  // but the entry attributes may change over time
  final String uri, mimeType;
-  final int pageId, rotationDegrees;
+  final int? pageId;
+  final int rotationDegrees;
  final bool isFlipped;
  final int dateModifiedSecs;
  final double extent;

  const ThumbnailProviderKey({
-    @required this.uri,
-    @required this.mimeType,
-    @required this.pageId,
-    @required this.rotationDegrees,
-    @required this.isFlipped,
-    @required this.dateModifiedSecs,
+    required this.uri,
+    required this.mimeType,
+    required this.pageId,
+    required this.rotationDegrees,
+    required this.isFlipped,
+    required this.dateModifiedSecs,
    this.extent = 0,
-  })  : assert(uri != null),
-        assert(mimeType != null),
-        assert(rotationDegrees != null),
-        assert(isFlipped != null),
-        assert(dateModifiedSecs != null),
-        assert(extent != null);
+  });

  @override
  bool operator ==(Object other) {
--- a/lib/image_providers/uri_image_provider.dart
+++ b/lib/image_providers/uri_image_provider.dart
@ -8,20 +8,19 @@ import 'package:pedantic/pedantic.dart';

 class UriImage extends ImageProvider<UriImage> {
  final String uri, mimeType;
-  final int pageId, rotationDegrees, expectedContentLength;
+  final int? pageId, rotationDegrees, expectedContentLength;
  final bool isFlipped;
  final double scale;

  const UriImage({
-    @required this.uri,
-    @required this.mimeType,
-    @required this.pageId,
-    @required this.rotationDegrees,
-    @required this.isFlipped,
+    required this.uri,
+    required this.mimeType,
+    required this.pageId,
+    required this.rotationDegrees,
+    required this.isFlipped,
    this.expectedContentLength,
    this.scale = 1.0,
-  })  : assert(uri != null),
-        assert(scale != null);
+  });

  @override
  Future<UriImage> obtainKey(ImageConfiguration configuration) {
@ -60,7 +59,7 @@ class UriImage extends ImageProvider<UriImage> {
          ));
        },
      );
-      if (bytes == null) {
+      if (bytes.isEmpty) {
        throw StateError('$uri ($mimeType) loading failed');
      }
      return await decode(bytes);
--- a/lib/image_providers/uri_picture_provider.dart
+++ b/lib/image_providers/uri_picture_provider.dart
@ -2,15 +2,13 @@ import 'package:aves/services/services.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_svg/flutter_svg.dart';
-import 'package:pedantic/pedantic.dart';

 class UriPicture extends PictureProvider<UriPicture> {
  const UriPicture({
-    @required this.uri,
-    @required this.mimeType,
-    ColorFilter colorFilter,
-  })  : assert(uri != null),
-        super(colorFilter);
+    required this.uri,
+    required this.mimeType,
+    ColorFilter? colorFilter,
+  }) : super(colorFilter);

  final String uri, mimeType;

@ -20,25 +18,30 @@ class UriPicture extends PictureProvider<UriPicture> {
  }

  @override
-  PictureStreamCompleter load(UriPicture key, {PictureErrorListener onError}) {
+  PictureStreamCompleter load(UriPicture key, {PictureErrorListener? onError}) {
    return OneFramePictureStreamCompleter(_loadAsync(key, onError: onError), informationCollector: () sync* {
      yield DiagnosticsProperty<String>('uri', uri);
    });
  }

-  Future<PictureInfo> _loadAsync(UriPicture key, {PictureErrorListener onError}) async {
+  Future<PictureInfo?> _loadAsync(UriPicture key, {PictureErrorListener? onError}) async {
    assert(key == this);

    final data = await imageFileService.getSvg(uri, mimeType);
-    if (data == null || data.isEmpty) {
+    if (data.isEmpty) {
      return null;
    }

    final decoder = SvgPicture.svgByteDecoder;
    if (onError != null) {
-      final future = decoder(data, colorFilter, key.toString());
-      unawaited(future.catchError(onError));
-      return future;
+      return decoder(
+        data,
+        colorFilter,
+        key.toString(),
+      ).catchError((error, stack) async {
+        onError(error, stack);
+        return Future<PictureInfo>.error(error, stack);
+      });
    }
    return decoder(data, colorFilter, key.toString());
  }
--- a/lib/l10n/app_en.arb
+++ b/lib/l10n/app_en.arb
@ -18,6 +18,8 @@
  "@applyButtonLabel": {},
  "deleteButtonLabel": "DELETE",
  "@deleteButtonLabel": {},
+  "showButtonLabel": "SHOW",
+  "@showButtonLabel": {},
  "hideButtonLabel": "HIDE",
  "@hideButtonLabel": {},
  "continueButtonLabel": "CONTINUE",
@ -555,9 +557,9 @@
  "@settingsVideoEnableHardwareAcceleration": {},
  "settingsVideoEnableAutoPlay": "Auto play",
  "@settingsVideoEnableAutoPlay": {},
-  "settingsVideoLoopModeTile":  "Loop mode",
+  "settingsVideoLoopModeTile": "Loop mode",
  "@settingsVideoLoopModeTile": {},
-  "settingsVideoLoopModeTitle":  "Loop Mode",
+  "settingsVideoLoopModeTitle": "Loop Mode",
  "@settingsVideoLoopModeTitle": {},

  "settingsSectionPrivacy": "Privacy",
--- a/lib/l10n/app_ko.arb
+++ b/lib/l10n/app_ko.arb
@ -7,6 +7,7 @@

  "applyButtonLabel": "확인",
  "deleteButtonLabel": "삭제",
+  "showButtonLabel": "보기",
  "hideButtonLabel": "숨기기",
  "continueButtonLabel": "다음",
  "clearTooltip": "초기화",
@ -259,8 +260,8 @@
  "settingsVideoShowVideos": "미디어에 동영상 표시",
  "settingsVideoEnableHardwareAcceleration": "하드웨어 가속",
  "settingsVideoEnableAutoPlay": "자동 재생",
-  "settingsVideoLoopModeTile":  "반복 모드",
-  "settingsVideoLoopModeTitle":  "반복 모드",
+  "settingsVideoLoopModeTile": "반복 모드",
+  "settingsVideoLoopModeTitle": "반복 모드",

  "settingsSectionPrivacy": "개인정보 보호",
  "settingsEnableAnalytics": "진단 데이터 보내기",
--- a/lib/main.dart
+++ b/lib/main.dart
@ -1,36 +1,26 @@
+// @dart=2.9
 import 'dart:isolate';
-import 'dart:ui';

-import 'package:aves/app_mode.dart';
-import 'package:aves/model/settings/settings.dart';
-import 'package:aves/model/source/collection_source.dart';
-import 'package:aves/model/source/media_store_source.dart';
-import 'package:aves/services/services.dart';
-import 'package:aves/theme/durations.dart';
-import 'package:aves/theme/icons.dart';
-import 'package:aves/theme/themes.dart';
-import 'package:aves/utils/debouncer.dart';
-import 'package:aves/widgets/common/behaviour/route_tracker.dart';
-import 'package:aves/widgets/common/behaviour/routes.dart';
-import 'package:aves/widgets/common/extensions/build_context.dart';
-import 'package:aves/widgets/common/providers/highlight_info_provider.dart';
-import 'package:aves/widgets/home_page.dart';
-import 'package:aves/widgets/welcome_page.dart';
-import 'package:firebase_analytics/firebase_analytics.dart';
-import 'package:firebase_analytics/observer.dart';
-import 'package:firebase_core/firebase_core.dart';
+import 'package:aves/widgets/aves_app.dart';
 import 'package:firebase_crashlytics/firebase_crashlytics.dart';
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter/services.dart';
-import 'package:flutter_gen/gen_l10n/app_localizations.dart';
-import 'package:overlay_support/overlay_support.dart';
-import 'package:provider/provider.dart';

 void main() {
 //  HttpClient.enableTimelineLogging = true; // enable network traffic logging
 //  debugPrintGestureArenaDiagnostics = true;

+// Invert oversized images (debug mode only)
+// cf https://flutter.dev/docs/development/tools/devtools/inspector
+// but unaware of device pixel ratio as of Flutter 2.2.1: https://github.com/flutter/flutter/issues/76208
+//
+// MaterialApp.checkerboardOffscreenLayers
+// cf https://flutter.dev/docs/perf/rendering/ui-performance#checking-for-offscreen-layers
+//
+// MaterialApp.checkerboardRasterCacheImages
+// cf https://flutter.dev/docs/perf/rendering/ui-performance#checking-for-non-cached-images
+//
+// flutter run --profile --trace-skia
+
  Isolate.current.addErrorListener(RawReceivePort((pair) async {
    final List<dynamic> errorAndStacktrace = pair;
    await FirebaseCrashlytics.instance.recordError(
@ -41,147 +31,3 @@ void main() {

  runApp(AvesApp());
 }
-
-class AvesApp extends StatefulWidget {
-  @override
-  _AvesAppState createState() => _AvesAppState();
-}
-
-class _AvesAppState extends State<AvesApp> {
-  final ValueNotifier<AppMode> appModeNotifier = ValueNotifier(AppMode.main);
-  Future<void> _appSetup;
-  final _mediaStoreSource = MediaStoreSource();
-  final Debouncer _contentChangeDebouncer = Debouncer(delay: Durations.contentChangeDebounceDelay);
-  final Set<String> changedUris = {};
-
-  // observers are not registered when using the same list object with different items
-  // the list itself needs to be reassigned
-  List<NavigatorObserver> _navigatorObservers = [];
-  final EventChannel _contentChangeChannel = EventChannel('deckers.thibault/aves/contentchange');
-  final EventChannel _newIntentChannel = EventChannel('deckers.thibault/aves/intent');
-  final GlobalKey<NavigatorState> _navigatorKey = GlobalKey(debugLabel: 'app-navigator');
-
-  Widget getFirstPage({Map intentData}) => settings.hasAcceptedTerms ? HomePage(intentData: intentData) : WelcomePage();
-
-  @override
-  void initState() {
-    super.initState();
-    initPlatformServices();
-    _appSetup = _setup();
-    _contentChangeChannel.receiveBroadcastStream().listen((event) => _onContentChange(event as String));
-    _newIntentChannel.receiveBroadcastStream().listen((event) => _onNewIntent(event as Map));
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    // place the settings provider above `MaterialApp`
-    // so it can be used during navigation transitions
-    return ChangeNotifierProvider<Settings>.value(
-      value: settings,
-      child: ListenableProvider<ValueNotifier<AppMode>>.value(
-        value: appModeNotifier,
-        child: Provider<CollectionSource>.value(
-          value: _mediaStoreSource,
-          child: HighlightInfoProvider(
-            child: OverlaySupport(
-              child: FutureBuilder<void>(
-                future: _appSetup,
-                builder: (context, snapshot) {
-                  final initialized = !snapshot.hasError && snapshot.connectionState == ConnectionState.done;
-                  final home = initialized
-                      ? getFirstPage()
-                      : Scaffold(
-                          body: snapshot.hasError ? _buildError(snapshot.error) : SizedBox(),
-                        );
-                  return Selector<Settings, Locale>(
-                      selector: (context, s) => s.locale,
-                      builder: (context, settingsLocale, child) {
-                        return MaterialApp(
-                          navigatorKey: _navigatorKey,
-                          home: home,
-                          navigatorObservers: _navigatorObservers,
-                          onGenerateTitle: (context) => context.l10n.appName,
-                          darkTheme: Themes.darkTheme,
-                          themeMode: ThemeMode.dark,
-                          locale: settingsLocale,
-                          localizationsDelegates: [
-                            ...AppLocalizations.localizationsDelegates,
-                          ],
-                          supportedLocales: AppLocalizations.supportedLocales,
-                        );
-                      });
-                },
-              ),
-            ),
-          ),
-        ),
-      ),
-    );
-  }
-
-  Widget _buildError(Object error) {
-    return Container(
-      alignment: Alignment.center,
-      padding: EdgeInsets.all(16),
-      child: Column(
-        mainAxisSize: MainAxisSize.min,
-        children: [
-          Icon(AIcons.error),
-          SizedBox(height: 16),
-          Text(error.toString()),
-        ],
-      ),
-    );
-  }
-
-  Future<void> _setup() async {
-    await Firebase.initializeApp().then((app) {
-      final crashlytics = FirebaseCrashlytics.instance;
-      FlutterError.onError = crashlytics.recordFlutterError;
-      crashlytics.setCustomKey('locales', window.locales.join(', '));
-      final now = DateTime.now();
-      crashlytics.setCustomKey('timezone', '${now.timeZoneName} (${now.timeZoneOffset})');
-      crashlytics.setCustomKey(
-          'build_mode',
-          kReleaseMode
-              ? 'release'
-              : kProfileMode
-                  ? 'profile'
-                  : 'debug');
-    });
-    await settings.init();
-    await settings.initFirebase();
-    _navigatorObservers = [
-      FirebaseAnalyticsObserver(analytics: FirebaseAnalytics()),
-      CrashlyticsRouteTracker(),
-    ];
-  }
-
-  void _onNewIntent(Map intentData) {
-    debugPrint('$runtimeType onNewIntent with intentData=$intentData');
-
-    // do not reset when relaunching the app
-    if (appModeNotifier.value == AppMode.main && (intentData == null || intentData.isEmpty == true)) return;
-
-    FirebaseCrashlytics.instance.log('New intent');
-    _navigatorKey.currentState.pushReplacement(DirectMaterialPageRoute(
-      settings: RouteSettings(name: HomePage.routeName),
-      builder: (_) => getFirstPage(intentData: intentData),
-    ));
-  }
-
-  void _onContentChange(String uri) {
-    if (uri != null) changedUris.add(uri);
-    if (changedUris.isNotEmpty) {
-      _contentChangeDebouncer(() async {
-        final todo = changedUris.toSet();
-        changedUris.clear();
-        final tempUris = await _mediaStoreSource.refreshUris(todo);
-        if (tempUris.isNotEmpty) {
-          changedUris.addAll(tempUris);
-          _onContentChange(null);
-        }
-      });
-    }
-  }
-}
--- a/lib/model/actions/chip_actions.dart
+++ b/lib/model/actions/chip_actions.dart
@ -42,7 +42,6 @@ extension ExtraChipAction on ChipAction {
      case ChipAction.setCover:
        return context.l10n.chipActionSetCover;
    }
-    return null;
  }

  IconData getIcon() {
@ -65,6 +64,5 @@ extension ExtraChipAction on ChipAction {
      case ChipAction.setCover:
        return AIcons.setCover;
    }
-    return null;
  }
 }
--- a/lib/model/actions/entry_actions.dart
+++ b/lib/model/actions/entry_actions.dart
@ -91,10 +91,9 @@ extension ExtraEntryAction on EntryAction {
      case EntryAction.debug:
        return 'Debug';
    }
-    return null;
  }

-  IconData getIcon() {
+  IconData? getIcon() {
    switch (this) {
      // in app actions
      case EntryAction.toggleFavourite:
@ -129,6 +128,5 @@ extension ExtraEntryAction on EntryAction {
      case EntryAction.debug:
        return AIcons.debug;
    }
-    return null;
  }
 }
--- a/lib/model/availability.dart
+++ b/lib/model/availability.dart
@ -1,11 +1,11 @@
 import 'package:aves/model/settings/settings.dart';
 import 'package:aves/theme/durations.dart';
-import 'package:connectivity/connectivity.dart';
+import 'package:connectivity_plus/connectivity_plus.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:github/github.dart';
 import 'package:google_api_availability/google_api_availability.dart';
-import 'package:package_info/package_info.dart';
+import 'package:package_info_plus/package_info_plus.dart';
 import 'package:version/version.dart';

 abstract class AvesAvailability {
@ -21,7 +21,7 @@ abstract class AvesAvailability {
 }

 class LiveAvesAvailability implements AvesAvailability {
-  bool _isConnected, _hasPlayServices, _isNewVersionAvailable;
+  bool? _isConnected, _hasPlayServices, _isNewVersionAvailable;

  LiveAvesAvailability() {
    Connectivity().onConnectivityChanged.listen(_updateConnectivityFromResult);
@ -32,10 +32,10 @@ class LiveAvesAvailability implements AvesAvailability {

  @override
  Future<bool> get isConnected async {
-    if (_isConnected != null) return SynchronousFuture(_isConnected);
+    if (_isConnected != null) return SynchronousFuture(_isConnected!);
    final result = await (Connectivity().checkConnectivity());
    _updateConnectivityFromResult(result);
-    return _isConnected;
+    return _isConnected!;
  }

  void _updateConnectivityFromResult(ConnectivityResult result) {
@ -48,11 +48,11 @@ class LiveAvesAvailability implements AvesAvailability {

  @override
  Future<bool> get hasPlayServices async {
-    if (_hasPlayServices != null) return SynchronousFuture(_hasPlayServices);
+    if (_hasPlayServices != null) return SynchronousFuture(_hasPlayServices!);
    final result = await GoogleApiAvailability.instance.checkGooglePlayServicesAvailability();
    _hasPlayServices = result == GooglePlayServicesAvailability.success;
    debugPrint('Device has Play Services=$_hasPlayServices');
-    return _hasPlayServices;
+    return _hasPlayServices!;
  }

  // local geocoding with `geocoder` requires Play Services
@ -61,27 +61,27 @@ class LiveAvesAvailability implements AvesAvailability {

  @override
  Future<bool> get isNewVersionAvailable async {
-    if (_isNewVersionAvailable != null) return SynchronousFuture(_isNewVersionAvailable);
+    if (_isNewVersionAvailable != null) return SynchronousFuture(_isNewVersionAvailable!);

    final now = DateTime.now();
    final dueDate = settings.lastVersionCheckDate.add(Durations.lastVersionCheckInterval);
    if (now.isBefore(dueDate)) {
      _isNewVersionAvailable = false;
-      return SynchronousFuture(_isNewVersionAvailable);
+      return SynchronousFuture(_isNewVersionAvailable!);
    }

    if (!(await isConnected)) return false;

    Version version(String s) => Version.parse(s.replaceFirst('v', ''));
    final currentTag = (await PackageInfo.fromPlatform()).version;
-    final latestTag = (await GitHub().repositories.getLatestRelease(RepositorySlug('deckerst', 'aves'))).tagName;
+    final latestTag = (await GitHub().repositories.getLatestRelease(RepositorySlug('deckerst', 'aves'))).tagName!;
    _isNewVersionAvailable = version(latestTag) > version(currentTag);
-    if (_isNewVersionAvailable) {
+    if (_isNewVersionAvailable!) {
      debugPrint('Aves $latestTag is available on github');
    } else {
      debugPrint('Aves $currentTag is the latest version');
      settings.lastVersionCheckDate = now;
    }
-    return _isNewVersionAvailable;
+    return _isNewVersionAvailable!;
  }
 }
--- a/lib/model/covers.dart
+++ b/lib/model/covers.dart
@ -2,6 +2,7 @@ import 'package:aves/model/entry.dart';
 import 'package:aves/model/filters/album.dart';
 import 'package:aves/model/filters/filters.dart';
 import 'package:aves/services/services.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

@ -18,19 +19,19 @@ class Covers with ChangeNotifier {

  int get count => _rows.length;

-  int coverContentId(CollectionFilter filter) => _rows.firstWhere((row) => row.filter == filter, orElse: () => null)?.contentId;
+  int? coverContentId(CollectionFilter filter) => _rows.firstWhereOrNull((row) => row.filter == filter)?.contentId;

-  Future<void> set(CollectionFilter filter, int contentId) async {
+  Future<void> set(CollectionFilter filter, int? contentId) async {
    // erase contextual properties from filters before saving them
    if (filter is AlbumFilter) {
-      filter = AlbumFilter((filter as AlbumFilter).album, null);
+      filter = AlbumFilter(filter.album, null);
    }

-    final row = CoverRow(filter: filter, contentId: contentId);
    _rows.removeWhere((row) => row.filter == filter);
    if (contentId == null) {
-      await metadataDb.removeCovers({row});
+      await metadataDb.removeCovers({filter});
    } else {
+      final row = CoverRow(filter: filter, contentId: contentId);
      _rows.add(row);
      await metadataDb.addCovers({row});
    }
@ -46,11 +47,11 @@ class Covers with ChangeNotifier {
      final filter = oldRow.filter;
      _rows.remove(oldRow);
      if (filter.test(entry)) {
-        final newRow = CoverRow(filter: filter, contentId: entry.contentId);
+        final newRow = CoverRow(filter: filter, contentId: entry.contentId!);
        await metadataDb.updateCoverEntryId(oldRow.contentId, newRow);
        _rows.add(newRow);
      } else {
-        await metadataDb.removeCovers({oldRow});
+        await metadataDb.removeCovers({filter});
      }
    }

@ -61,7 +62,7 @@ class Covers with ChangeNotifier {
    final contentIds = entries.map((entry) => entry.contentId).toSet();
    final removedRows = _rows.where((row) => contentIds.contains(row.contentId)).toSet();

-    await metadataDb.removeCovers(removedRows);
+    await metadataDb.removeCovers(removedRows.map((row) => row.filter).toSet());
    _rows.removeAll(removedRows);

    notifyListeners();
@ -81,13 +82,15 @@ class CoverRow {
  final int contentId;

  const CoverRow({
-    @required this.filter,
-    @required this.contentId,
+    required this.filter,
+    required this.contentId,
  });

-  factory CoverRow.fromMap(Map map) {
+  static CoverRow? fromMap(Map map) {
+    final filter = CollectionFilter.fromJson(map['filter']);
+    if (filter == null) return null;
    return CoverRow(
-      filter: CollectionFilter.fromJson(map['filter']),
+      filter: filter,
      contentId: map['contentId'],
    );
  }
--- a/lib/model/entry.dart
+++ b/lib/model/entry.dart
@ -22,22 +22,22 @@ import '../ref/mime_types.dart';

 class AvesEntry {
  String uri;
-  String _path, _directory, _filename, _extension;
-  int pageId, contentId;
+  String? _path, _directory, _filename, _extension;
+  int? pageId, contentId;
  final String sourceMimeType;
  int width;
  int height;
  int sourceRotationDegrees;
-  final int sizeBytes;
-  String _sourceTitle;
+  final int? sizeBytes;
+  String? _sourceTitle;

  // `dateModifiedSecs` can be missing in viewer mode
-  int _dateModifiedSecs;
-  final int sourceDateTakenMillis;
-  final int durationMillis;
-  int _catalogDateMillis;
-  CatalogMetadata _catalogMetadata;
-  AddressDetails _addressDetails;
+  int? _dateModifiedSecs;
+  final int? sourceDateTakenMillis;
+  final int? durationMillis;
+  int? _catalogDateMillis;
+  CatalogMetadata? _catalogMetadata;
+  AddressDetails? _addressDetails;

  final AChangeNotifier imageChangeNotifier = AChangeNotifier(), metadataChangeNotifier = AChangeNotifier(), addressChangeNotifier = AChangeNotifier();

@ -51,21 +51,20 @@ class AvesEntry {
  ];

  AvesEntry({
-    this.uri,
-    String path,
-    this.contentId,
-    this.pageId,
-    this.sourceMimeType,
-    @required this.width,
-    @required this.height,
-    this.sourceRotationDegrees,
-    this.sizeBytes,
-    String sourceTitle,
-    int dateModifiedSecs,
-    this.sourceDateTakenMillis,
-    this.durationMillis,
-  })  : assert(width != null),
-        assert(height != null) {
+    required this.uri,
+    required String? path,
+    required this.contentId,
+    required this.pageId,
+    required this.sourceMimeType,
+    required this.width,
+    required this.height,
+    required this.sourceRotationDegrees,
+    required this.sizeBytes,
+    required String? sourceTitle,
+    required int? dateModifiedSecs,
+    required this.sourceDateTakenMillis,
+    required this.durationMillis,
+  }) {
    this.path = path;
    this.sourceTitle = sourceTitle;
    this.dateModifiedSecs = dateModifiedSecs;
@ -76,16 +75,17 @@ class AvesEntry {
  bool get canHaveAlpha => MimeTypes.alphaImages.contains(mimeType);

  AvesEntry copyWith({
-    String uri,
-    String path,
-    int contentId,
-    int dateModifiedSecs,
+    String? uri,
+    String? path,
+    int? contentId,
+    int? dateModifiedSecs,
  }) {
    final copyContentId = contentId ?? this.contentId;
    final copied = AvesEntry(
      uri: uri ?? this.uri,
      path: path ?? this.path,
      contentId: copyContentId,
+      pageId: null,
      sourceMimeType: sourceMimeType,
      width: width,
      height: height,
@ -106,17 +106,18 @@ class AvesEntry {
  factory AvesEntry.fromMap(Map map) {
    return AvesEntry(
      uri: map['uri'] as String,
-      path: map['path'] as String,
-      contentId: map['contentId'] as int,
+      path: map['path'] as String?,
+      pageId: null,
+      contentId: map['contentId'] as int?,
      sourceMimeType: map['sourceMimeType'] as String,
-      width: map['width'] as int ?? 0,
-      height: map['height'] as int ?? 0,
-      sourceRotationDegrees: map['sourceRotationDegrees'] as int ?? 0,
-      sizeBytes: map['sizeBytes'] as int,
-      sourceTitle: map['title'] as String,
-      dateModifiedSecs: map['dateModifiedSecs'] as int,
-      sourceDateTakenMillis: map['sourceDateTakenMillis'] as int,
-      durationMillis: map['durationMillis'] as int,
+      width: map['width'] as int? ?? 0,
+      height: map['height'] as int? ?? 0,
+      sourceRotationDegrees: map['sourceRotationDegrees'] as int? ?? 0,
+      sizeBytes: map['sizeBytes'] as int?,
+      sourceTitle: map['title'] as String?,
+      dateModifiedSecs: map['dateModifiedSecs'] as int?,
+      sourceDateTakenMillis: map['sourceDateTakenMillis'] as int?,
+      durationMillis: map['durationMillis'] as int?,
    );
  }

@ -150,27 +151,27 @@ class AvesEntry {
  @override
  String toString() => '$runtimeType#${shortHash(this)}{uri=$uri, path=$path, pageId=$pageId}';

-  set path(String path) {
+  set path(String? path) {
    _path = path;
    _directory = null;
    _filename = null;
    _extension = null;
  }

-  String get path => _path;
+  String? get path => _path;

-  String get directory {
-    _directory ??= path != null ? pContext.dirname(path) : null;
+  String? get directory {
+    _directory ??= path != null ? pContext.dirname(path!) : null;
    return _directory;
  }

-  String get filenameWithoutExtension {
-    _filename ??= path != null ? pContext.basenameWithoutExtension(path) : null;
+  String? get filenameWithoutExtension {
+    _filename ??= path != null ? pContext.basenameWithoutExtension(path!) : null;
    return _filename;
  }

-  String get extension {
-    _extension ??= path != null ? pContext.extension(path) : null;
+  String? get extension {
+    _extension ??= path != null ? pContext.extension(path!) : null;
    return _extension;
  }

@ -258,16 +259,16 @@ class AvesEntry {
  static const ratioSeparator = '\u2236';
  static const resolutionSeparator = ' \u00D7 ';

-  bool get isSized => (width ?? 0) > 0 && (height ?? 0) > 0;
+  bool get isSized => width > 0 && height > 0;

  String get resolutionText {
-    final ws = width ?? '?';
-    final hs = height ?? '?';
+    final ws = width;
+    final hs = height;
    return isRotated ? '$hs$resolutionSeparator$ws' : '$ws$resolutionSeparator$hs';
  }

  String get aspectRatioText {
-    if (width != null && height != null && width > 0 && height > 0) {
+    if (width > 0 && height > 0) {
      final gcd = width.gcd(height);
      final w = width ~/ gcd;
      final h = height ~/ gcd;
@ -288,24 +289,36 @@ class AvesEntry {
    return isRotated ? Size(h, w) : Size(w, h);
  }

-  int get megaPixels => width != null && height != null ? (width * height / 1000000).round() : null;
+  Size videoDisplaySize(double sar) {
+    final size = displaySize;
+    if (sar != 1) {
+      final dar = displayAspectRatio * sar;
+      final w = size.width;
+      final h = size.height;
+      if (w >= h) return Size(w, w / dar);
+      if (h > w) return Size(h * dar, h);
+    }
+    return size;
+  }

-  DateTime _bestDate;
+  int get megaPixels => (width * height / 1000000).round();

-  DateTime get bestDate {
+  DateTime? _bestDate;
+
+  DateTime? get bestDate {
    if (_bestDate == null) {
      if ((_catalogDateMillis ?? 0) > 0) {
-        _bestDate = DateTime.fromMillisecondsSinceEpoch(_catalogDateMillis);
+        _bestDate = DateTime.fromMillisecondsSinceEpoch(_catalogDateMillis!);
      } else if ((sourceDateTakenMillis ?? 0) > 0) {
-        _bestDate = DateTime.fromMillisecondsSinceEpoch(sourceDateTakenMillis);
+        _bestDate = DateTime.fromMillisecondsSinceEpoch(sourceDateTakenMillis!);
      } else if ((dateModifiedSecs ?? 0) > 0) {
-        _bestDate = DateTime.fromMillisecondsSinceEpoch(dateModifiedSecs * 1000);
+        _bestDate = DateTime.fromMillisecondsSinceEpoch(dateModifiedSecs! * 1000);
      }
    }
    return _bestDate;
  }

-  int get rotationDegrees => _catalogMetadata?.rotationDegrees ?? sourceRotationDegrees ?? 0;
+  int get rotationDegrees => _catalogMetadata?.rotationDegrees ?? sourceRotationDegrees;

  set rotationDegrees(int rotationDegrees) {
    sourceRotationDegrees = rotationDegrees;
@ -316,78 +329,78 @@ class AvesEntry {

  set isFlipped(bool isFlipped) => _catalogMetadata?.isFlipped = isFlipped;

-  String get sourceTitle => _sourceTitle;
+  String? get sourceTitle => _sourceTitle;

-  set sourceTitle(String sourceTitle) {
+  set sourceTitle(String? sourceTitle) {
    _sourceTitle = sourceTitle;
    _bestTitle = null;
  }

-  int get dateModifiedSecs => _dateModifiedSecs;
+  int? get dateModifiedSecs => _dateModifiedSecs;

-  set dateModifiedSecs(int dateModifiedSecs) {
+  set dateModifiedSecs(int? dateModifiedSecs) {
    _dateModifiedSecs = dateModifiedSecs;
    _bestDate = null;
  }

-  DateTime get monthTaken {
+  DateTime? get monthTaken {
    final d = bestDate;
    return d == null ? null : DateTime(d.year, d.month);
  }

-  DateTime get dayTaken {
+  DateTime? get dayTaken {
    final d = bestDate;
    return d == null ? null : DateTime(d.year, d.month, d.day);
  }

-  String _durationText;
+  String? _durationText;

  String get durationText {
    _durationText ??= formatFriendlyDuration(Duration(milliseconds: durationMillis ?? 0));
-    return _durationText;
+    return _durationText!;
  }

  // returns whether this entry has GPS coordinates
  // (0, 0) coordinates are considered invalid, as it is likely a default value
-  bool get hasGps => _catalogMetadata != null && _catalogMetadata.latitude != null && _catalogMetadata.longitude != null && (_catalogMetadata.latitude != 0 || _catalogMetadata.longitude != 0);
+  bool get hasGps => (_catalogMetadata?.latitude ?? 0) != 0 || (_catalogMetadata?.longitude ?? 0) != 0;

  bool get hasAddress => _addressDetails != null;

  // has a place, or at least the full country name
  // derived from Google reverse geocoding addresses
-  bool get hasFineAddress => _addressDetails != null && (_addressDetails.place?.isNotEmpty == true || (_addressDetails.countryName?.length ?? 0) > 3);
+  bool get hasFineAddress => _addressDetails?.place?.isNotEmpty == true || (_addressDetails?.countryName?.length ?? 0) > 3;

-  LatLng get latLng => hasGps ? LatLng(_catalogMetadata.latitude, _catalogMetadata.longitude) : null;
+  LatLng? get latLng => hasGps ? LatLng(_catalogMetadata!.latitude!, _catalogMetadata!.longitude!) : null;

-  String get geoUri {
+  String? get geoUri {
    if (!hasGps) return null;
-    final latitude = roundToPrecision(_catalogMetadata.latitude, decimals: 6);
-    final longitude = roundToPrecision(_catalogMetadata.longitude, decimals: 6);
+    final latitude = roundToPrecision(_catalogMetadata!.latitude!, decimals: 6);
+    final longitude = roundToPrecision(_catalogMetadata!.longitude!, decimals: 6);
    return 'geo:$latitude,$longitude?q=$latitude,$longitude';
  }

-  List<String> _xmpSubjects;
+  List<String>? _xmpSubjects;

  List<String> get xmpSubjects {
-    _xmpSubjects ??= _catalogMetadata?.xmpSubjects?.split(';')?.where((tag) => tag.isNotEmpty)?.toList() ?? [];
-    return _xmpSubjects;
+    _xmpSubjects ??= _catalogMetadata?.xmpSubjects?.split(';').where((tag) => tag.isNotEmpty).toList() ?? [];
+    return _xmpSubjects!;
  }

-  String _bestTitle;
+  String? _bestTitle;

-  String get bestTitle {
-    _bestTitle ??= _catalogMetadata?.xmpTitleDescription?.isNotEmpty == true ? _catalogMetadata.xmpTitleDescription : sourceTitle;
+  String? get bestTitle {
+    _bestTitle ??= _catalogMetadata?.xmpTitleDescription?.isNotEmpty == true ? _catalogMetadata!.xmpTitleDescription : sourceTitle;
    return _bestTitle;
  }

-  CatalogMetadata get catalogMetadata => _catalogMetadata;
+  CatalogMetadata? get catalogMetadata => _catalogMetadata;

-  set catalogDateMillis(int dateMillis) {
+  set catalogDateMillis(int? dateMillis) {
    _catalogDateMillis = dateMillis;
    _bestDate = null;
  }

-  set catalogMetadata(CatalogMetadata newMetadata) {
+  set catalogMetadata(CatalogMetadata? newMetadata) {
    final oldDateModifiedSecs = dateModifiedSecs;
    final oldRotationDegrees = rotationDegrees;
    final oldIsFlipped = isFlipped;
@ -424,14 +437,14 @@ class AvesEntry {
    }
  }

-  AddressDetails get addressDetails => _addressDetails;
+  AddressDetails? get addressDetails => _addressDetails;

-  set addressDetails(AddressDetails newAddress) {
+  set addressDetails(AddressDetails? newAddress) {
    _addressDetails = newAddress;
    addressChangeNotifier.notifyListeners();
  }

-  Future<void> locate({@required bool background}) async {
+  Future<void> locate({required bool background}) async {
    if (!hasGps) return;
    await _locateCountry();
    if (await availability.canLocatePlaces) {
@ -442,11 +455,11 @@ class AvesEntry {
  // quick reverse geocoding to find the country, using an offline asset
  Future<void> _locateCountry() async {
    if (!hasGps || hasAddress) return;
-    final countryCode = await countryTopology.countryCode(latLng);
+    final countryCode = await countryTopology.countryCode(latLng!);
    setCountry(countryCode);
  }

-  void setCountry(CountryCode countryCode) {
+  void setCountry(CountryCode? countryCode) {
    if (hasFineAddress || countryCode == null) return;
    addressDetails = AddressDetails(
      contentId: contentId,
@ -455,25 +468,25 @@ class AvesEntry {
    );
  }

-  String _geocoderLocale;
+  String? _geocoderLocale;

  String get geocoderLocale {
-    _geocoderLocale ??= (settings.locale ?? WidgetsBinding.instance.window.locale).toString();
-    return _geocoderLocale;
+    _geocoderLocale ??= (settings.locale ?? WidgetsBinding.instance!.window.locale).toString();
+    return _geocoderLocale!;
  }

  // full reverse geocoding, requiring Play Services and some connectivity
-  Future<void> locatePlace({@required bool background}) async {
+  Future<void> locatePlace({required bool background}) async {
    if (!hasGps || hasFineAddress) return;
    try {
-      Future<List<Address>> call() => GeocodingService.getAddress(latLng, geocoderLocale);
+      Future<List<Address>> call() => GeocodingService.getAddress(latLng!, geocoderLocale);
      final addresses = await (background
          ? servicePolicy.call(
              call,
              priority: ServiceCallPriority.getLocation,
            )
          : call());
-      if (addresses != null && addresses.isNotEmpty) {
+      if (addresses.isNotEmpty) {
        final address = addresses.first;
        final cc = address.countryCode;
        final cn = address.countryName;
@ -493,12 +506,12 @@ class AvesEntry {
    }
  }

-  Future<String> findAddressLine() async {
+  Future<String?> findAddressLine() async {
    if (!hasGps) return null;

    try {
-      final addresses = await GeocodingService.getAddress(latLng, geocoderLocale);
-      if (addresses != null && addresses.isNotEmpty) {
+      final addresses = await GeocodingService.getAddress(latLng!, geocoderLocale);
+      if (addresses.isNotEmpty) {
        final address = addresses.first;
        return address.addressLine;
      }
@ -549,12 +562,12 @@ class AvesEntry {
    if (isFlipped is bool) this.isFlipped = isFlipped;

    await metadataDb.saveEntries({this});
-    await metadataDb.saveMetadata({catalogMetadata});
+    if (catalogMetadata != null) await metadataDb.saveMetadata({catalogMetadata!});

    metadataChangeNotifier.notifyListeners();
  }

-  Future<bool> rotate({@required bool clockwise}) async {
+  Future<bool> rotate({required bool clockwise}) async {
    final newFields = await imageFileService.rotate(this, clockwise: clockwise);
    if (newFields.isEmpty) return false;

@ -579,7 +592,7 @@ class AvesEntry {
  }

  Future<bool> delete() {
-    Completer completer = Completer<bool>();
+    final completer = Completer<bool>();
    imageFileService.delete([this]).listen(
      (event) => completer.complete(event.success),
      onError: completer.completeError,
@ -593,7 +606,7 @@ class AvesEntry {
  }

  // when the entry image itself changed (e.g. after rotation)
-  Future<void> _onImageChanged(int oldDateModifiedSecs, int oldRotationDegrees, bool oldIsFlipped) async {
+  Future<void> _onImageChanged(int? oldDateModifiedSecs, int oldRotationDegrees, bool oldIsFlipped) async {
    if (oldDateModifiedSecs != dateModifiedSecs || oldRotationDegrees != rotationDegrees || oldIsFlipped != isFlipped) {
      await EntryCache.evict(uri, mimeType, oldDateModifiedSecs, oldRotationDegrees, oldIsFlipped);
      imageChangeNotifier.notifyListeners();
@ -626,15 +639,15 @@ class AvesEntry {
  // 1) title ascending
  // 2) extension ascending
  static int compareByName(AvesEntry a, AvesEntry b) {
-    final c = compareAsciiUpperCase(a.bestTitle, b.bestTitle);
-    return c != 0 ? c : compareAsciiUpperCase(a.extension, b.extension);
+    final c = compareAsciiUpperCase(a.bestTitle ?? '', b.bestTitle ?? '');
+    return c != 0 ? c : compareAsciiUpperCase(a.extension ?? '', b.extension ?? '');
  }

  // compare by:
  // 1) size descending
  // 2) name ascending
  static int compareBySize(AvesEntry a, AvesEntry b) {
-    final c = b.sizeBytes.compareTo(a.sizeBytes);
+    final c = (b.sizeBytes ?? 0).compareTo(a.sizeBytes ?? 0);
    return c != 0 ? c : compareByName(a, b);
  }

--- a/lib/model/entry_cache.dart
+++ b/lib/model/entry_cache.dart
@ -1,19 +1,29 @@
 import 'dart:async';
-import 'dart:math';

 import 'package:aves/image_providers/thumbnail_provider.dart';
 import 'package:aves/image_providers/uri_image_provider.dart';

 class EntryCache {
+  // ordered descending
+  static final thumbnailRequestExtents = <double>[];
+
+  static void markThumbnailExtent(double extent) {
+    if (!thumbnailRequestExtents.contains(extent)) {
+      thumbnailRequestExtents
+        ..add(extent)
+        ..sort((a, b) => b.compareTo(a));
+    }
+  }
+
  static Future<void> evict(
    String uri,
    String mimeType,
-    int dateModifiedSecs,
+    int? dateModifiedSecs,
    int oldRotationDegrees,
    bool oldIsFlipped,
  ) async {
    // TODO TLAD provide pageId parameter for multi page items, if someday image editing features are added for them
-    int pageId;
+    int? pageId;

    // evict fullscreen image
    await UriImage(
@ -29,20 +39,18 @@ class EntryCache {
      uri: uri,
      mimeType: mimeType,
      pageId: pageId,
-      dateModifiedSecs: dateModifiedSecs,
+      dateModifiedSecs: dateModifiedSecs ?? 0,
      rotationDegrees: oldRotationDegrees,
      isFlipped: oldIsFlipped,
    )).evict();

-    // evict higher quality thumbnails (with powers of 2 from 32 to 1024 as specified extents)
-    final extents = List.generate(6, (index) => pow(2, index + 5).toDouble());
    await Future.forEach<double>(
-        extents,
+        thumbnailRequestExtents,
        (extent) => ThumbnailProvider(ThumbnailProviderKey(
              uri: uri,
              mimeType: mimeType,
              pageId: pageId,
-              dateModifiedSecs: dateModifiedSecs,
+              dateModifiedSecs: dateModifiedSecs ?? 0,
              rotationDegrees: oldRotationDegrees,
              isFlipped: oldIsFlipped,
              extent: extent,
--- a/lib/model/entry_images.dart
+++ b/lib/model/entry_images.dart
@ -5,7 +5,8 @@ import 'package:aves/image_providers/region_provider.dart';
 import 'package:aves/image_providers/thumbnail_provider.dart';
 import 'package:aves/image_providers/uri_image_provider.dart';
 import 'package:aves/model/entry.dart';
-import 'package:flutter/foundation.dart';
+import 'package:aves/model/entry_cache.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/widgets.dart';

 extension ExtraAvesEntry on AvesEntry {
@ -14,11 +15,7 @@ extension ExtraAvesEntry on AvesEntry {
  }

  ThumbnailProviderKey _getThumbnailProviderKey(double extent) {
-    // we standardize the thumbnail loading dimension by taking the nearest larger power of 2
-    // so that there are less variants of the thumbnails to load and cache
-    // it increases the chance of cache hit when loading similarly sized columns (e.g. on orientation change)
-    final requestExtent = extent == 0 ? .0 : pow(2, (log(extent) / log(2)).ceil()).toDouble();
-
+    EntryCache.markThumbnailExtent(extent);
    return ThumbnailProviderKey(
      uri: uri,
      mimeType: mimeType,
@ -26,15 +23,15 @@ extension ExtraAvesEntry on AvesEntry {
      rotationDegrees: rotationDegrees,
      isFlipped: isFlipped,
      dateModifiedSecs: dateModifiedSecs ?? -1,
-      extent: requestExtent,
+      extent: extent,
    );
  }

-  RegionProvider getRegion({@required int sampleSize, Rectangle<int> region}) {
+  RegionProvider getRegion({required int sampleSize, Rectangle<int>? region}) {
    return RegionProvider(_getRegionProviderKey(sampleSize, region));
  }

-  RegionProviderKey _getRegionProviderKey(int sampleSize, Rectangle<int> region) {
+  RegionProviderKey _getRegionProviderKey(int sampleSize, Rectangle<int>? region) {
    return RegionProviderKey(
      uri: uri,
      mimeType: mimeType,
@ -56,12 +53,12 @@ extension ExtraAvesEntry on AvesEntry {
        expectedContentLength: sizeBytes,
      );

-  bool _isReady(Object providerKey) => imageCache.statusForKey(providerKey).keepAlive;
+  bool _isReady(Object providerKey) => imageCache!.statusForKey(providerKey).keepAlive;

-  ImageProvider getBestThumbnail(double extent) {
-    final sizedThumbnailKey = _getThumbnailProviderKey(extent);
-    if (_isReady(sizedThumbnailKey)) return ThumbnailProvider(sizedThumbnailKey);
+  List<ThumbnailProvider> get cachedThumbnails => EntryCache.thumbnailRequestExtents.map(_getThumbnailProviderKey).where(_isReady).map((key) => ThumbnailProvider(key)).toList();

-    return getThumbnail();
+  ThumbnailProvider get bestCachedThumbnail {
+    final sizedThumbnailKey = EntryCache.thumbnailRequestExtents.map(_getThumbnailProviderKey).firstWhereOrNull(_isReady);
+    return sizedThumbnailKey != null ? ThumbnailProvider(sizedThumbnailKey) : getThumbnail();
  }
 }
--- a/lib/model/favourites.dart
+++ b/lib/model/favourites.dart
@ -1,5 +1,6 @@
 import 'package:aves/model/entry.dart';
 import 'package:aves/services/services.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

@ -18,7 +19,7 @@ class Favourites with ChangeNotifier {

  bool isFavourite(AvesEntry entry) => _rows.any((row) => row.contentId == entry.contentId);

-  FavouriteRow _entryToRow(AvesEntry entry) => FavouriteRow(contentId: entry.contentId, path: entry.path);
+  FavouriteRow _entryToRow(AvesEntry entry) => FavouriteRow(contentId: entry.contentId!, path: entry.path!);

  Future<void> add(Iterable<AvesEntry> entries) async {
    final newRows = entries.map(_entryToRow);
@ -40,7 +41,7 @@ class Favourites with ChangeNotifier {
  }

  Future<void> moveEntry(int oldContentId, AvesEntry entry) async {
-    final oldRow = _rows.firstWhere((row) => row.contentId == oldContentId, orElse: () => null);
+    final oldRow = _rows.firstWhereOrNull((row) => row.contentId == oldContentId);
    if (oldRow == null) return;

    final newRow = _entryToRow(entry);
@ -66,13 +67,13 @@ class FavouriteRow {
  final String path;

  const FavouriteRow({
-    this.contentId,
-    this.path,
+    required this.contentId,
+    required this.path,
  });

  factory FavouriteRow.fromMap(Map map) {
    return FavouriteRow(
-      contentId: map['contentId'],
+      contentId: map['contentId'] ?? 0,
      path: map['path'] ?? '',
    );
  }
--- a/lib/model/filters/album.dart
+++ b/lib/model/filters/album.dart
@ -14,7 +14,7 @@ class AlbumFilter extends CollectionFilter {
  static final Map<String, Color> _appColors = {};

  final String album;
-  final String displayName;
+  final String? displayName;

  const AlbumFilter(this.album, this.displayName);

@ -41,10 +41,10 @@ class AlbumFilter extends CollectionFilter {
  String getTooltip(BuildContext context) => album;

  @override
-  Widget iconBuilder(BuildContext context, double size, {bool showGenericIcon = true, bool embossed = false}) {
+  Widget? iconBuilder(BuildContext context, double size, {bool showGenericIcon = true, bool embossed = false}) {
    return IconUtils.getAlbumIcon(
          context: context,
-          album: album,
+          albumPath: album,
          size: size,
          embossed: embossed,
        ) ??
@ -56,21 +56,20 @@ class AlbumFilter extends CollectionFilter {
    // do not use async/await and rely on `SynchronousFuture`
    // to prevent rebuilding of the `FutureBuilder` listening on this future
    if (androidFileUtils.getAlbumType(album) == AlbumType.app) {
-      if (_appColors.containsKey(album)) return SynchronousFuture(_appColors[album]);
+      if (_appColors.containsKey(album)) return SynchronousFuture(_appColors[album]!);

-      return PaletteGenerator.fromImageProvider(
-        AppIconImage(
-          packageName: androidFileUtils.getAlbumAppPackageName(album),
-          size: 24,
-        ),
-      ).then((palette) {
-        final color = palette.dominantColor?.color ?? super.color(context);
-        _appColors[album] = color;
-        return color;
-      });
-    } else {
-      return super.color(context);
+      final packageName = androidFileUtils.getAlbumAppPackageName(album);
+      if (packageName != null) {
+        return PaletteGenerator.fromImageProvider(
+          AppIconImage(packageName: packageName, size: 24),
+        ).then((palette) async {
+          final color = palette.dominantColor?.color ?? (await super.color(context));
+          _appColors[album] = color;
+          return color;
+        });
+      }
    }
+    return super.color(context);
  }

  @override
--- a/lib/model/filters/filters.dart
+++ b/lib/model/filters/filters.dart
@ -24,7 +24,7 @@ abstract class CollectionFilter implements Comparable<CollectionFilter> {
    TagFilter.type,
  ];

-  static CollectionFilter fromJson(String jsonString) {
+  static CollectionFilter? fromJson(String jsonString) {
    final jsonMap = jsonDecode(jsonString);
    final type = jsonMap['type'];
    switch (type) {
@ -63,7 +63,7 @@ abstract class CollectionFilter implements Comparable<CollectionFilter> {

  String getTooltip(BuildContext context) => getLabel(context);

-  Widget iconBuilder(BuildContext context, double size, {bool showGenericIcon = true, bool embossed = false});
+  Widget? iconBuilder(BuildContext context, double size, {bool showGenericIcon = true, bool embossed = false});

  Future<Color> color(BuildContext context) => SynchronousFuture(stringToColor(getLabel(context)));

@ -84,7 +84,7 @@ abstract class CollectionFilter implements Comparable<CollectionFilter> {

 class FilterGridItem<T extends CollectionFilter> {
  final T filter;
-  final AvesEntry entry;
+  final AvesEntry? entry;

  const FilterGridItem(this.filter, this.entry);

--- a/lib/model/filters/location.dart
+++ b/lib/model/filters/location.dart
@ -1,6 +1,7 @@
 import 'package:aves/model/filters/filters.dart';
 import 'package:aves/theme/icons.dart';
 import 'package:aves/widgets/common/extensions/build_context.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

@ -10,8 +11,8 @@ class LocationFilter extends CollectionFilter {

  final LocationLevel level;
  String _location;
-  String _countryCode;
-  EntryFilter _test;
+  String? _countryCode;
+  late EntryFilter _test;

  LocationFilter(this.level, this._location) {
    final split = _location.split(locationSeparator);
@ -29,7 +30,7 @@ class LocationFilter extends CollectionFilter {

  LocationFilter.fromMap(Map<String, dynamic> json)
      : this(
-          LocationLevel.values.firstWhere((v) => v.toString() == json['level'], orElse: () => null),
+          LocationLevel.values.firstWhereOrNull((v) => v.toString() == json['level']) ?? LocationLevel.place,
          json['location'],
        );

@ -42,7 +43,7 @@ class LocationFilter extends CollectionFilter {

  String get countryNameAndCode => '$_location$locationSeparator$_countryCode';

-  String get countryCode => _countryCode;
+  String? get countryCode => _countryCode;

  @override
  EntryFilter get test => _test;
@ -90,8 +91,9 @@ class LocationFilter extends CollectionFilter {
  // U+1F1E6 🇦 REGIONAL INDICATOR SYMBOL LETTER A
  static const _countryCodeToFlagDiff = 0x1F1E6 - 0x0041;

-  static String countryCodeToFlag(String code) {
-    return code?.length == 2 ? String.fromCharCodes(code.codeUnits.map((letter) => letter += _countryCodeToFlagDiff)) : null;
+  static String? countryCodeToFlag(String? code) {
+    if (code == null || code.length != 2) return null;
+    return String.fromCharCodes(code.codeUnits.map((letter) => letter += _countryCodeToFlagDiff));
  }
 }

--- a/lib/model/filters/mime.dart
+++ b/lib/model/filters/mime.dart
@ -10,9 +10,9 @@ class MimeFilter extends CollectionFilter {
  static const type = 'mime';

  final String mime;
-  EntryFilter _test;
-  String _label;
-  IconData _icon;
+  late EntryFilter _test;
+  late String _label;
+  IconData? /*late*/ _icon;

  static final image = MimeFilter(MimeTypes.anyImage);
  static final video = MimeFilter(MimeTypes.anyVideo);
--- a/lib/model/filters/query.dart
+++ b/lib/model/filters/query.dart
@ -12,7 +12,7 @@ class QueryFilter extends CollectionFilter {

  final String query;
  final bool colorful;
-  EntryFilter _test;
+  late EntryFilter _test;

  QueryFilter(this.query, {this.colorful = true}) {
    var upQuery = query.toUpperCase();
@ -26,7 +26,7 @@ class QueryFilter extends CollectionFilter {
    // allow untrimmed queries wrapped with `"..."`
    final matches = exactRegex.allMatches(upQuery);
    if (matches.length == 1) {
-      upQuery = matches.first.group(1);
+      upQuery = matches.first.group(1)!;
    }

    _test = not ? (entry) => !entry.search(upQuery) : (entry) => entry.search(upQuery);
--- a/lib/model/filters/tag.dart
+++ b/lib/model/filters/tag.dart
@ -8,7 +8,7 @@ class TagFilter extends CollectionFilter {
  static const type = 'tag';

  final String tag;
-  EntryFilter _test;
+  late EntryFilter _test;

  TagFilter(this.tag) {
    if (tag.isEmpty) {
@ -42,7 +42,7 @@ class TagFilter extends CollectionFilter {
  String getLabel(BuildContext context) => tag.isEmpty ? context.l10n.filterTagEmptyLabel : tag;

  @override
-  Widget iconBuilder(BuildContext context, double size, {bool showGenericIcon = true, bool embossed = false}) => showGenericIcon ? Icon(tag.isEmpty ? AIcons.tagOff : AIcons.tag, size: size) : null;
+  Widget? iconBuilder(BuildContext context, double size, {bool showGenericIcon = true, bool embossed = false}) => showGenericIcon ? Icon(tag.isEmpty ? AIcons.tagOff : AIcons.tag, size: size) : null;

  @override
  String get category => type;
--- a/lib/model/filters/type.dart
+++ b/lib/model/filters/type.dart
@ -14,8 +14,8 @@ class TypeFilter extends CollectionFilter {
  static const _sphericalVideo = 'spherical_video'; // subset of videos

  final String itemType;
-  EntryFilter _test;
-  IconData _icon;
+  late EntryFilter _test;
+  IconData? /*late*/ _icon;

  static final animated = TypeFilter._private(_animated);
  static final geotiff = TypeFilter._private(_geotiff);
--- a/lib/model/highlight.dart
+++ b/lib/model/highlight.dart
@ -1,7 +1,29 @@
+import 'package:event_bus/event_bus.dart';
 import 'package:flutter/foundation.dart';
+import 'package:flutter/widgets.dart';

 class HighlightInfo extends ChangeNotifier {
-  Object _item;
+  final EventBus eventBus = EventBus();
+
+  void trackItem<T>(
+    T? item, {
+    TrackPredicate? predicate,
+    Alignment? alignment,
+    bool? animate,
+    Object? highlightItem,
+  }) {
+    if (item != null) {
+      eventBus.fire(TrackEvent<T>(
+        item,
+        predicate ?? (_) => true,
+        alignment ?? Alignment.center,
+        animate ?? true,
+        highlightItem,
+      ));
+    }
+  }
+
+  Object? _item;

  void set(Object item) {
    if (_item == item) return;
@ -9,7 +31,7 @@ class HighlightInfo extends ChangeNotifier {
    notifyListeners();
  }

-  Object clear() {
+  Object? clear() {
    if (_item == null) return null;
    final item = _item;
    _item = null;
@ -22,3 +44,24 @@ class HighlightInfo extends ChangeNotifier {
  @override
  String toString() => '$runtimeType#${shortHash(this)}{item=$_item}';
 }
+
+@immutable
+class TrackEvent<T> {
+  final T item;
+  final TrackPredicate predicate;
+  final Alignment alignment;
+  final bool animate;
+  final Object? highlightItem;
+
+  const TrackEvent(
+    this.item,
+    this.predicate,
+    this.alignment,
+    this.animate,
+    this.highlightItem,
+  );
+}
+
+// `itemVisibility`: percent of the item tracked already visible in viewport
+// return whether to proceed with tracking
+typedef TrackPredicate = bool Function(double itemVisibility);
--- a/lib/model/metadata.dart
+++ b/lib/model/metadata.dart
@ -4,7 +4,7 @@ import 'package:flutter/widgets.dart';
 import 'package:intl/intl.dart';

 class DateMetadata {
-  final int contentId, dateMillis;
+  final int? contentId, dateMillis;

  DateMetadata({
    this.contentId,
@ -28,13 +28,13 @@ class DateMetadata {
 }

 class CatalogMetadata {
-  final int contentId, dateMillis;
+  final int? contentId, dateMillis;
  final bool isAnimated, isGeotiff, is360, isMultiPage;
  bool isFlipped;
-  int rotationDegrees;
-  final String mimeType, xmpSubjects, xmpTitleDescription;
-  double latitude, longitude;
-  Address address;
+  int? rotationDegrees;
+  final String? mimeType, xmpSubjects, xmpTitleDescription;
+  double? latitude, longitude;
+  Address? address;

  static const double _precisionErrorTolerance = 1e-9;
  static const _isAnimatedMask = 1 << 0;
@ -55,23 +55,28 @@ class CatalogMetadata {
    this.rotationDegrees,
    this.xmpSubjects,
    this.xmpTitleDescription,
-    double latitude,
-    double longitude,
+    double? latitude,
+    double? longitude,
  }) {
-    // Geocoder throws an `IllegalArgumentException` when a coordinate has a funky values like `1.7056881853375E7`
+    // Geocoder throws an `IllegalArgumentException` when a coordinate has a funky value like `1.7056881853375E7`
    // We also exclude zero coordinates, taking into account precision errors (e.g. {5.952380952380953e-11,-2.7777777777777777e-10}),
    // but Flutter's `precisionErrorTolerance` (1e-10) is slightly too lenient for this case.
    if (latitude != null && longitude != null && (latitude.abs() > _precisionErrorTolerance || longitude.abs() > _precisionErrorTolerance)) {
-      this.latitude = latitude < -90.0 || latitude > 90.0 ? null : latitude;
-      this.longitude = longitude < -180.0 || longitude > 180.0 ? null : longitude;
+      // funny case: some files have latitude and longitude reverse
+      // (e.g. a Japanese location at lat~=133 and long~=34, which is a valid longitude but an invalid latitude)
+      // so we should check and assign both coordinates at once
+      if (latitude >= -90.0 && latitude <= 90.0 && longitude >= -180.0 && longitude <= 180.0) {
+        this.latitude = latitude;
+        this.longitude = longitude;
+      }
    }
  }

  CatalogMetadata copyWith({
-    int contentId,
-    String mimeType,
-    bool isMultiPage,
-    int rotationDegrees,
+    int? contentId,
+    String? mimeType,
+    bool? isMultiPage,
+    int? rotationDegrees,
  }) {
    return CatalogMetadata(
      contentId: contentId ?? this.contentId,
@ -127,16 +132,16 @@ class CatalogMetadata {
 }

 class OverlayMetadata {
-  final String aperture, exposureTime, focalLength, iso;
+  final String? aperture, exposureTime, focalLength, iso;

  static final apertureFormat = NumberFormat('0.0', 'en_US');
  static final focalLengthFormat = NumberFormat('0.#', 'en_US');

  OverlayMetadata({
-    double aperture,
-    String exposureTime,
-    double focalLength,
-    int iso,
+    double? aperture,
+    String? exposureTime,
+    double? focalLength,
+    int? iso,
  })  : aperture = aperture != null ? 'ƒ/${apertureFormat.format(aperture)}' : null,
        exposureTime = exposureTime,
        focalLength = focalLength != null ? '${focalLengthFormat.format(focalLength)} mm' : null,
@ -144,10 +149,10 @@ class OverlayMetadata {

  factory OverlayMetadata.fromMap(Map map) {
    return OverlayMetadata(
-      aperture: map['aperture'] as double,
-      exposureTime: map['exposureTime'] as String,
-      focalLength: map['focalLength'] as double,
-      iso: map['iso'] as int,
+      aperture: map['aperture'] as double?,
+      exposureTime: map['exposureTime'] as String?,
+      focalLength: map['focalLength'] as double?,
+      iso: map['iso'] as int?,
    );
  }

@ -159,10 +164,10 @@ class OverlayMetadata {

@immutable
 class AddressDetails {
-  final int contentId;
-  final String countryCode, countryName, adminArea, locality;
+  final int? contentId;
+  final String? countryCode, countryName, adminArea, locality;

-  String get place => locality != null && locality.isNotEmpty ? locality : adminArea;
+  String? get place => locality != null && locality!.isNotEmpty ? locality : adminArea;

  const AddressDetails({
    this.contentId,
@ -173,7 +178,7 @@ class AddressDetails {
  });

  AddressDetails copyWith({
-    int contentId,
+    int? contentId,
  }) {
    return AddressDetails(
      contentId: contentId ?? this.contentId,
@ -186,11 +191,11 @@ class AddressDetails {

  factory AddressDetails.fromMap(Map map) {
    return AddressDetails(
-      contentId: map['contentId'],
-      countryCode: map['countryCode'] ?? '',
-      countryName: map['countryName'] ?? '',
-      adminArea: map['adminArea'] ?? '',
-      locality: map['locality'] ?? '',
+      contentId: map['contentId'] as int?,
+      countryCode: map['countryCode'] as String?,
+      countryName: map['countryName'] as String?,
+      adminArea: map['adminArea'] as String?,
+      locality: map['locality'] as String?,
    );
  }

--- a/lib/model/metadata_db.dart
+++ b/lib/model/metadata_db.dart
@ -3,6 +3,7 @@ import 'dart:io';
 import 'package:aves/model/covers.dart';
 import 'package:aves/model/entry.dart';
 import 'package:aves/model/favourites.dart';
+import 'package:aves/model/filters/filters.dart';
 import 'package:aves/model/metadata.dart';
 import 'package:aves/model/metadata_db_upgrade.dart';
 import 'package:aves/services/services.dart';
@ -16,7 +17,7 @@ abstract class MetadataDb {

  Future<void> reset();

-  Future<void> removeIds(Set<int> contentIds, {@required bool metadataOnly});
+  Future<void> removeIds(Set<int> contentIds, {required bool metadataOnly});

  // entries

@ -40,9 +41,9 @@ abstract class MetadataDb {

  Future<List<CatalogMetadata>> loadMetadataEntries();

-  Future<void> saveMetadata(Iterable<CatalogMetadata> metadataEntries);
+  Future<void> saveMetadata(Set<CatalogMetadata> metadataEntries);

-  Future<void> updateMetadataId(int oldId, CatalogMetadata metadata);
+  Future<void> updateMetadataId(int oldId, CatalogMetadata? metadata);

  // address

@ -50,9 +51,9 @@ abstract class MetadataDb {

  Future<List<AddressDetails>> loadAddresses();

-  Future<void> saveAddresses(Iterable<AddressDetails> addresses);
+  Future<void> saveAddresses(Set<AddressDetails> addresses);

-  Future<void> updateAddressId(int oldId, AddressDetails address);
+  Future<void> updateAddressId(int oldId, AddressDetails? address);

  // favourites

@ -76,11 +77,11 @@ abstract class MetadataDb {

  Future<void> updateCoverEntryId(int oldId, CoverRow row);

-  Future<void> removeCovers(Iterable<CoverRow> rows);
+  Future<void> removeCovers(Set<CollectionFilter> filters);
 }

 class SqfliteMetadataDb implements MetadataDb {
-  Future<Database> _database;
+  late Future<Database> _database;

  Future<String> get path async => pContext.join(await getDatabasesPath(), 'metadata.db');

@ -150,8 +151,8 @@ class SqfliteMetadataDb implements MetadataDb {

  @override
  Future<int> dbFileSize() async {
-    final file = File((await path));
-    return await file.exists() ? file.length() : 0;
+    final file = File(await path);
+    return await file.exists() ? await file.length() : 0;
  }

  @override
@ -163,8 +164,8 @@ class SqfliteMetadataDb implements MetadataDb {
  }

  @override
-  Future<void> removeIds(Set<int> contentIds, {@required bool metadataOnly}) async {
-    if (contentIds == null || contentIds.isEmpty) return;
+  Future<void> removeIds(Set<int> contentIds, {required bool metadataOnly}) async {
+    if (contentIds.isEmpty) return;

    final stopwatch = Stopwatch()..start();
    final db = await _database;
@ -207,7 +208,7 @@ class SqfliteMetadataDb implements MetadataDb {

  @override
  Future<void> saveEntries(Iterable<AvesEntry> entries) async {
-    if (entries == null || entries.isEmpty) return;
+    if (entries.isEmpty) return;
    final stopwatch = Stopwatch()..start();
    final db = await _database;
    final batch = db.batch();
@ -226,7 +227,6 @@ class SqfliteMetadataDb implements MetadataDb {
  }

  void _batchInsertEntry(Batch batch, AvesEntry entry) {
-    if (entry == null) return;
    batch.insert(
      entryTable,
      entry.toMap(),
@ -273,13 +273,13 @@ class SqfliteMetadataDb implements MetadataDb {
  }

  @override
-  Future<void> saveMetadata(Iterable<CatalogMetadata> metadataEntries) async {
-    if (metadataEntries == null || metadataEntries.isEmpty) return;
+  Future<void> saveMetadata(Set<CatalogMetadata> metadataEntries) async {
+    if (metadataEntries.isEmpty) return;
    final stopwatch = Stopwatch()..start();
    try {
      final db = await _database;
      final batch = db.batch();
-      metadataEntries.where((metadata) => metadata != null).forEach((metadata) => _batchInsertMetadata(batch, metadata));
+      metadataEntries.forEach((metadata) => _batchInsertMetadata(batch, metadata));
      await batch.commit(noResult: true);
      debugPrint('$runtimeType saveMetadata complete in ${stopwatch.elapsed.inMilliseconds}ms for ${metadataEntries.length} entries');
    } catch (error, stack) {
@ -288,7 +288,7 @@ class SqfliteMetadataDb implements MetadataDb {
  }

  @override
-  Future<void> updateMetadataId(int oldId, CatalogMetadata metadata) async {
+  Future<void> updateMetadataId(int oldId, CatalogMetadata? metadata) async {
    final db = await _database;
    final batch = db.batch();
    batch.delete(dateTakenTable, where: 'contentId = ?', whereArgs: [oldId]);
@ -297,7 +297,7 @@ class SqfliteMetadataDb implements MetadataDb {
    await batch.commit(noResult: true);
  }

-  void _batchInsertMetadata(Batch batch, CatalogMetadata metadata) {
+  void _batchInsertMetadata(Batch batch, CatalogMetadata? metadata) {
    if (metadata == null) return;
    if (metadata.dateMillis != 0) {
      batch.insert(
@ -333,18 +333,18 @@ class SqfliteMetadataDb implements MetadataDb {
  }

  @override
-  Future<void> saveAddresses(Iterable<AddressDetails> addresses) async {
-    if (addresses == null || addresses.isEmpty) return;
+  Future<void> saveAddresses(Set<AddressDetails> addresses) async {
+    if (addresses.isEmpty) return;
    final stopwatch = Stopwatch()..start();
    final db = await _database;
    final batch = db.batch();
-    addresses.where((address) => address != null).forEach((address) => _batchInsertAddress(batch, address));
+    addresses.forEach((address) => _batchInsertAddress(batch, address));
    await batch.commit(noResult: true);
    debugPrint('$runtimeType saveAddresses complete in ${stopwatch.elapsed.inMilliseconds}ms for ${addresses.length} entries');
  }

  @override
-  Future<void> updateAddressId(int oldId, AddressDetails address) async {
+  Future<void> updateAddressId(int oldId, AddressDetails? address) async {
    final db = await _database;
    final batch = db.batch();
    batch.delete(addressTable, where: 'contentId = ?', whereArgs: [oldId]);
@ -352,7 +352,7 @@ class SqfliteMetadataDb implements MetadataDb {
    await batch.commit(noResult: true);
  }

-  void _batchInsertAddress(Batch batch, AddressDetails address) {
+  void _batchInsertAddress(Batch batch, AddressDetails? address) {
    if (address == null) return;
    batch.insert(
      addressTable,
@ -380,10 +380,10 @@ class SqfliteMetadataDb implements MetadataDb {

  @override
  Future<void> addFavourites(Iterable<FavouriteRow> rows) async {
-    if (rows == null || rows.isEmpty) return;
+    if (rows.isEmpty) return;
    final db = await _database;
    final batch = db.batch();
-    rows.where((row) => row != null).forEach((row) => _batchInsertFavourite(batch, row));
+    rows.forEach((row) => _batchInsertFavourite(batch, row));
    await batch.commit(noResult: true);
  }

@ -397,7 +397,6 @@ class SqfliteMetadataDb implements MetadataDb {
  }

  void _batchInsertFavourite(Batch batch, FavouriteRow row) {
-    if (row == null) return;
    batch.insert(
      favouriteTable,
      row.toMap(),
@ -407,8 +406,8 @@ class SqfliteMetadataDb implements MetadataDb {

  @override
  Future<void> removeFavourites(Iterable<FavouriteRow> rows) async {
-    if (rows == null || rows.isEmpty) return;
-    final ids = rows.where((row) => row != null).map((row) => row.contentId);
+    if (rows.isEmpty) return;
+    final ids = rows.map((row) => row.contentId);
    if (ids.isEmpty) return;

    final db = await _database;
@ -431,16 +430,16 @@ class SqfliteMetadataDb implements MetadataDb {
  Future<Set<CoverRow>> loadCovers() async {
    final db = await _database;
    final maps = await db.query(coverTable);
-    final rows = maps.map((map) => CoverRow.fromMap(map)).toSet();
+    final rows = maps.map(CoverRow.fromMap).where((v) => v != null).cast<CoverRow>().toSet();
    return rows;
  }

  @override
  Future<void> addCovers(Iterable<CoverRow> rows) async {
-    if (rows == null || rows.isEmpty) return;
+    if (rows.isEmpty) return;
    final db = await _database;
    final batch = db.batch();
-    rows.where((row) => row != null).forEach((row) => _batchInsertCover(batch, row));
+    rows.forEach((row) => _batchInsertCover(batch, row));
    await batch.commit(noResult: true);
  }

@ -454,7 +453,6 @@ class SqfliteMetadataDb implements MetadataDb {
  }

  void _batchInsertCover(Batch batch, CoverRow row) {
-    if (row == null) return;
    batch.insert(
      coverTable,
      row.toMap(),
@ -463,9 +461,7 @@ class SqfliteMetadataDb implements MetadataDb {
  }

  @override
-  Future<void> removeCovers(Iterable<CoverRow> rows) async {
-    if (rows == null || rows.isEmpty) return;
-    final filters = rows.where((row) => row != null).map((row) => row.filter);
+  Future<void> removeCovers(Set<CollectionFilter> filters) async {
    if (filters.isEmpty) return;

    final db = await _database;
--- a/lib/model/multipage.dart
+++ b/lib/model/multipage.dart
@ -1,6 +1,7 @@
 import 'package:aves/model/entry.dart';
 import 'package:aves/ref/mime_types.dart';
 import 'package:aves/services/services.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';

 class MultiPageInfo {
@ -11,8 +12,8 @@ class MultiPageInfo {
  int get pageCount => _pages.length;

  MultiPageInfo({
-    @required this.mainEntry,
-    List<SinglePageInfo> pages,
+    required this.mainEntry,
+    required List<SinglePageInfo> pages,
  }) : _pages = pages {
    if (_pages.isNotEmpty) {
      _pages.sort();
@ -31,15 +32,15 @@ class MultiPageInfo {
    );
  }

-  SinglePageInfo get defaultPage => _pages.firstWhere((page) => page.isDefault, orElse: () => null);
+  SinglePageInfo? get defaultPage => _pages.firstWhereOrNull((page) => page.isDefault);

-  SinglePageInfo getById(int pageId) => _pages.firstWhere((page) => page.pageId == pageId, orElse: () => null);
+  SinglePageInfo? getById(int? pageId) => _pages.firstWhereOrNull((page) => page.pageId == pageId);

-  SinglePageInfo getByIndex(int pageIndex) => _pages.firstWhere((page) => page.index == pageIndex, orElse: () => null);
+  SinglePageInfo? getByIndex(int? pageIndex) => _pages.firstWhereOrNull((page) => page.index == pageIndex);

-  AvesEntry getPageEntryByIndex(int pageIndex) => _getPageEntry(getByIndex(pageIndex));
+  AvesEntry getPageEntryByIndex(int? pageIndex) => _getPageEntry(getByIndex(pageIndex));

-  AvesEntry _getPageEntry(SinglePageInfo pageInfo) {
+  AvesEntry _getPageEntry(SinglePageInfo? pageInfo) {
    if (pageInfo != null) {
      return _pageEntries.putIfAbsent(pageInfo, () => _createPageEntry(pageInfo));
    } else {
@ -52,20 +53,20 @@ class MultiPageInfo {
  List<AvesEntry> get exportEntries => _pages.map((pageInfo) => _createPageEntry(pageInfo, eraseDefaultPageId: false)).toList();

  Future<void> extractMotionPhotoVideo() async {
-    final videoPage = _pages.firstWhere((page) => page.isVideo, orElse: () => null);
+    final videoPage = _pages.firstWhereOrNull((page) => page.isVideo);
    if (videoPage != null && videoPage.uri == null) {
      final fields = await embeddedDataService.extractMotionPhotoVideo(mainEntry);
-      if (fields != null) {
+      if (fields.containsKey('uri')) {
        final pageIndex = _pages.indexOf(videoPage);
        _pages.removeAt(pageIndex);
        _pages.insert(
            pageIndex,
            videoPage.copyWith(
-              uri: fields['uri'] as String,
+              uri: fields['uri'] as String?,
              // the initial fake page may contain inaccurate values for the following fields
              // so we override them with values from the extracted standalone video
-              rotationDegrees: fields['sourceRotationDegrees'] as int,
-              durationMillis: fields['durationMillis'] as int,
+              rotationDegrees: fields['sourceRotationDegrees'] as int?,
+              durationMillis: fields['durationMillis'] as int?,
            ));
        _pageEntries.remove(videoPage);
      }
@ -83,9 +84,9 @@ class MultiPageInfo {
      path: mainEntry.path,
      contentId: mainEntry.contentId,
      pageId: pageId,
-      sourceMimeType: pageInfo.mimeType ?? mainEntry.sourceMimeType,
-      width: pageInfo.width ?? mainEntry.width,
-      height: pageInfo.height ?? mainEntry.height,
+      sourceMimeType: pageInfo.mimeType,
+      width: pageInfo.width,
+      height: pageInfo.height,
      sourceRotationDegrees: pageInfo.rotationDegrees ?? mainEntry.sourceRotationDegrees,
      sizeBytes: mainEntry.sizeBytes,
      sourceTitle: mainEntry.sourceTitle,
@ -108,26 +109,28 @@ class MultiPageInfo {
 class SinglePageInfo implements Comparable<SinglePageInfo> {
  final int index, pageId;
  final bool isDefault;
-  final String uri, mimeType;
-  final int width, height, rotationDegrees, durationMillis;
+  final String? uri;
+  final String mimeType;
+  final int width, height;
+  final int? rotationDegrees, durationMillis;

  const SinglePageInfo({
-    this.index,
-    this.pageId,
-    this.isDefault,
+    required this.index,
+    required this.pageId,
+    required this.isDefault,
    this.uri,
-    this.mimeType,
-    this.width,
-    this.height,
+    required this.mimeType,
+    required this.width,
+    required this.height,
    this.rotationDegrees,
    this.durationMillis,
  });

  SinglePageInfo copyWith({
-    bool isDefault,
-    String uri,
-    int rotationDegrees,
-    int durationMillis,
+    bool? isDefault,
+    String? uri,
+    int? rotationDegrees,
+    int? durationMillis,
  }) {
    return SinglePageInfo(
      index: index,
@ -147,12 +150,12 @@ class SinglePageInfo implements Comparable<SinglePageInfo> {
    return SinglePageInfo(
      index: index,
      pageId: index,
-      isDefault: map['isDefault'] as bool ?? false,
+      isDefault: map['isDefault'] as bool? ?? false,
      mimeType: map['mimeType'] as String,
-      width: map['width'] as int ?? 0,
-      height: map['height'] as int ?? 0,
-      rotationDegrees: map['rotationDegrees'] as int,
-      durationMillis: map['durationMillis'] as int,
+      width: map['width'] as int? ?? 0,
+      height: map['height'] as int? ?? 0,
+      rotationDegrees: map['rotationDegrees'] as int?,
+      durationMillis: map['durationMillis'] as int?,
    );
  }

--- a/lib/model/panorama.dart
+++ b/lib/model/panorama.dart
@ -2,9 +2,9 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

 class PanoramaInfo {
-  final Rect croppedAreaRect;
-  final Size fullPanoSize;
-  final String projectionType;
+  final Rect? croppedAreaRect;
+  final Size? fullPanoSize;
+  final String? projectionType;

  PanoramaInfo({
    this.croppedAreaRect,
@ -13,13 +13,13 @@ class PanoramaInfo {
  });

  factory PanoramaInfo.fromMap(Map map) {
-    var cLeft = map['croppedAreaLeft'] as int;
-    var cTop = map['croppedAreaTop'] as int;
-    final cWidth = map['croppedAreaWidth'] as int;
-    final cHeight = map['croppedAreaHeight'] as int;
-    var fWidth = map['fullPanoWidth'] as int;
-    var fHeight = map['fullPanoHeight'] as int;
-    final projectionType = map['projectionType'] as String;
+    var cLeft = map['croppedAreaLeft'] as int?;
+    var cTop = map['croppedAreaTop'] as int?;
+    final cWidth = map['croppedAreaWidth'] as int?;
+    final cHeight = map['croppedAreaHeight'] as int?;
+    var fWidth = map['fullPanoWidth'] as int?;
+    var fHeight = map['fullPanoHeight'] as int?;
+    final projectionType = map['projectionType'] as String?;

    // handle missing `fullPanoHeight` (e.g. Samsung camera app panorama mode)
    if (fHeight == null && cWidth != null && cHeight != null) {
@ -31,12 +31,12 @@ class PanoramaInfo {
      cLeft = 0;
    }

-    Rect croppedAreaRect;
+    Rect? croppedAreaRect;
    if (cLeft != null && cTop != null && cWidth != null && cHeight != null) {
      croppedAreaRect = Rect.fromLTWH(cLeft.toDouble(), cTop.toDouble(), cWidth.toDouble(), cHeight.toDouble());
    }

-    Size fullPanoSize;
+    Size? fullPanoSize;
    if (fWidth != null && fHeight != null) {
      fullPanoSize = Size(fWidth.toDouble(), fHeight.toDouble());
    }
--- a/lib/model/settings/entry_background.dart
+++ b/lib/model/settings/entry_background.dart
@ -15,12 +15,11 @@ extension ExtraEntryBackground on EntryBackground {

  Color get color {
    switch (this) {
-      case EntryBackground.black:
-        return Colors.black;
      case EntryBackground.white:
        return Colors.white;
+      case EntryBackground.black:
      default:
-        return null;
+        return Colors.black;
    }
  }
 }
--- a/lib/model/settings/settings.dart
+++ b/lib/model/settings/settings.dart
@ -1,6 +1,7 @@
 import 'package:aves/model/actions/entry_actions.dart';
 import 'package:aves/model/filters/filters.dart';
 import 'package:aves/model/settings/screen_on.dart';
+import 'package:collection/collection.dart';
 import 'package:firebase_analytics/firebase_analytics.dart';
 import 'package:firebase_core/firebase_core.dart';
 import 'package:firebase_crashlytics/firebase_crashlytics.dart';
@ -14,7 +15,7 @@ import 'enums.dart';
 final Settings settings = Settings._private();

 class Settings extends ChangeNotifier {
-  static SharedPreferences _prefs;
+  static SharedPreferences? /*late final*/ _prefs;

  Settings._private();

@ -93,7 +94,7 @@ class Settings extends ChangeNotifier {
  }

  Future<void> reset() {
-    return _prefs.clear();
+    return _prefs!.clear();
  }

  // app
@ -111,7 +112,7 @@ class Settings extends ChangeNotifier {

  static const localeSeparator = '-';

-  Locale get locale {
+  Locale? get locale {
    // exceptionally allow getting locale before settings are initialized
    final tag = _prefs?.getString(localeKey);
    if (tag != null) {
@ -125,11 +126,11 @@ class Settings extends ChangeNotifier {
    return null;
  }

-  set locale(Locale newValue) {
-    String tag;
+  set locale(Locale? newValue) {
+    String? tag;
    if (newValue != null) {
      tag = [
-        newValue.languageCode ?? '',
+        newValue.languageCode,
        newValue.scriptCode ?? '',
        newValue.countryCode ?? '',
      ].join(localeSeparator);
@ -152,11 +153,11 @@ class Settings extends ChangeNotifier {

  set homePage(HomePageSetting newValue) => setAndNotify(homePageKey, newValue.toString());

-  String get catalogTimeZone => _prefs.getString(catalogTimeZoneKey) ?? '';
+  String get catalogTimeZone => _prefs!.getString(catalogTimeZoneKey) ?? '';

  set catalogTimeZone(String newValue) => setAndNotify(catalogTimeZoneKey, newValue);

-  double getTileExtent(String routeName) => _prefs.getDouble(tileExtentPrefixKey + routeName) ?? 0;
+  double getTileExtent(String routeName) => _prefs!.getDouble(tileExtentPrefixKey + routeName) ?? 0;

  // do not notify, as tile extents are only used internally by `TileExtentController`
  // and should not trigger rebuilding by change notification
@ -202,11 +203,11 @@ class Settings extends ChangeNotifier {

  set tagSortFactor(ChipSortFactor newValue) => setAndNotify(tagSortFactorKey, newValue.toString());

-  Set<CollectionFilter> get pinnedFilters => (_prefs.getStringList(pinnedFiltersKey) ?? []).map(CollectionFilter.fromJson).toSet();
+  Set<CollectionFilter> get pinnedFilters => (_prefs!.getStringList(pinnedFiltersKey) ?? []).map(CollectionFilter.fromJson).where((v) => v != null).cast<CollectionFilter>().toSet();

  set pinnedFilters(Set<CollectionFilter> newValue) => setAndNotify(pinnedFiltersKey, newValue.map((filter) => filter.toJson()).toList());

-  Set<CollectionFilter> get hiddenFilters => (_prefs.getStringList(hiddenFiltersKey) ?? []).map(CollectionFilter.fromJson).toSet();
+  Set<CollectionFilter> get hiddenFilters => (_prefs!.getStringList(hiddenFiltersKey) ?? []).map(CollectionFilter.fromJson).where((v) => v != null).cast<CollectionFilter>().toSet();

  set hiddenFilters(Set<CollectionFilter> newValue) => setAndNotify(hiddenFiltersKey, newValue.map((filter) => filter.toJson()).toList());

@ -248,7 +249,7 @@ class Settings extends ChangeNotifier {

  set infoMapStyle(EntryMapStyle newValue) => setAndNotify(infoMapStyleKey, newValue.toString());

-  double get infoMapZoom => _prefs.getDouble(infoMapZoomKey) ?? 12;
+  double get infoMapZoom => _prefs!.getDouble(infoMapZoomKey) ?? 12;

  set infoMapZoom(double newValue) => setAndNotify(infoMapZoomKey, newValue);

@ -272,23 +273,23 @@ class Settings extends ChangeNotifier {

  set saveSearchHistory(bool newValue) => setAndNotify(saveSearchHistoryKey, newValue);

-  List<CollectionFilter> get searchHistory => (_prefs.getStringList(searchHistoryKey) ?? []).map(CollectionFilter.fromJson).toList();
+  List<CollectionFilter> get searchHistory => (_prefs!.getStringList(searchHistoryKey) ?? []).map(CollectionFilter.fromJson).where((v) => v != null).cast<CollectionFilter>().toList();

  set searchHistory(List<CollectionFilter> newValue) => setAndNotify(searchHistoryKey, newValue.map((filter) => filter.toJson()).toList());

  // version

-  DateTime get lastVersionCheckDate => DateTime.fromMillisecondsSinceEpoch(_prefs.getInt(lastVersionCheckDateKey) ?? 0);
+  DateTime get lastVersionCheckDate => DateTime.fromMillisecondsSinceEpoch(_prefs!.getInt(lastVersionCheckDateKey) ?? 0);

  set lastVersionCheckDate(DateTime newValue) => setAndNotify(lastVersionCheckDateKey, newValue.millisecondsSinceEpoch);

  // convenience methods

  // ignore: avoid_positional_boolean_parameters
-  bool getBoolOrDefault(String key, bool defaultValue) => _prefs.getKeys().contains(key) ? _prefs.getBool(key) : defaultValue;
+  bool getBoolOrDefault(String key, bool defaultValue) => _prefs!.getBool(key) ?? defaultValue;

  T getEnumOrDefault<T>(String key, T defaultValue, Iterable<T> values) {
-    final valueString = _prefs.getString(key);
+    final valueString = _prefs!.getString(key);
    for (final v in values) {
      if (v.toString() == valueString) {
        return v;
@ -298,28 +299,28 @@ class Settings extends ChangeNotifier {
  }

  List<T> getEnumListOrDefault<T>(String key, List<T> defaultValue, Iterable<T> values) {
-    return _prefs.getStringList(key)?.map((s) => values.firstWhere((v) => v.toString() == s, orElse: () => null))?.where((v) => v != null)?.toList() ?? defaultValue;
+    return _prefs!.getStringList(key)?.map((s) => values.firstWhereOrNull((v) => v.toString() == s)).where((v) => v != null).cast<T>().toList() ?? defaultValue;
  }

  void setAndNotify(String key, dynamic newValue, {bool notify = true}) {
-    var oldValue = _prefs.get(key);
+    var oldValue = _prefs!.get(key);
    if (newValue == null) {
-      _prefs.remove(key);
+      _prefs!.remove(key);
    } else if (newValue is String) {
-      oldValue = _prefs.getString(key);
-      _prefs.setString(key, newValue);
+      oldValue = _prefs!.getString(key);
+      _prefs!.setString(key, newValue);
    } else if (newValue is List<String>) {
-      oldValue = _prefs.getStringList(key);
-      _prefs.setStringList(key, newValue);
+      oldValue = _prefs!.getStringList(key);
+      _prefs!.setStringList(key, newValue);
    } else if (newValue is int) {
-      oldValue = _prefs.getInt(key);
-      _prefs.setInt(key, newValue);
+      oldValue = _prefs!.getInt(key);
+      _prefs!.setInt(key, newValue);
    } else if (newValue is double) {
-      oldValue = _prefs.getDouble(key);
-      _prefs.setDouble(key, newValue);
+      oldValue = _prefs!.getDouble(key);
+      _prefs!.setDouble(key, newValue);
    } else if (newValue is bool) {
-      oldValue = _prefs.getBool(key);
-      _prefs.setBool(key, newValue);
+      oldValue = _prefs!.getBool(key);
+      _prefs!.setBool(key, newValue);
    }
    if (oldValue != newValue && notify) {
      notifyListeners();
--- a/lib/model/settings/video_loop_mode.dart
+++ b/lib/model/settings/video_loop_mode.dart
@ -25,11 +25,10 @@ extension ExtraVideoLoopMode on VideoLoopMode {
      case VideoLoopMode.never:
        return false;
      case VideoLoopMode.shortOnly:
-        if (entry.durationMillis == null) return false;
-        return entry.durationMillis < shortVideoThreshold.inMilliseconds;
+        final durationMillis = entry.durationMillis;
+        return durationMillis != null ? durationMillis < shortVideoThreshold.inMilliseconds : false;
      case VideoLoopMode.always:
        return true;
    }
-    return false;
  }
 }
--- a/lib/model/source/album.dart
+++ b/lib/model/source/album.dart
@ -9,7 +9,7 @@ import 'package:collection/collection.dart';
 import 'package:flutter/widgets.dart';

 mixin AlbumMixin on SourceBase {
-  final Set<String> _directories = {};
+  final Set<String?> _directories = {};

  List<String> get rawAlbums => List.unmodifiable(_directories);

@ -25,7 +25,7 @@ mixin AlbumMixin on SourceBase {

  void _notifyAlbumChange() => eventBus.fire(AlbumsChangedEvent());

-  String getAlbumDisplayName(BuildContext context, String dirPath) {
+  String getAlbumDisplayName(BuildContext? context, String dirPath) {
    assert(!dirPath.endsWith(pContext.separator));

    if (context != null) {
@ -41,15 +41,15 @@ mixin AlbumMixin on SourceBase {

    final relativeDir = dir.relativeDir;
    if (relativeDir.isEmpty) {
-      final volume = androidFileUtils.getStorageVolume(dirPath);
+      final volume = androidFileUtils.getStorageVolume(dirPath)!;
      return volume.getDescription(context);
    }

-    String unique(String dirPath, Set<String> others) {
+    String unique(String dirPath, Set<String?> others) {
      final parts = pContext.split(dirPath);
      for (var i = parts.length - 1; i > 0; i--) {
        final testName = pContext.joinAll(['', ...parts.skip(i)]);
-        if (others.every((item) => !item.endsWith(testName))) return testName;
+        if (others.every((item) => !item!.endsWith(testName))) return testName;
      }
      return dirPath;
    }
@ -61,10 +61,10 @@ mixin AlbumMixin on SourceBase {
    }

    final volumePath = dir.volumePath;
-    String trimVolumePath(String path) => path.substring(dir.volumePath.length);
-    final otherAlbumsOnVolume = otherAlbumsOnDevice.where((path) => path.startsWith(volumePath)).map(trimVolumePath).toSet();
+    String trimVolumePath(String? path) => path!.substring(dir.volumePath.length);
+    final otherAlbumsOnVolume = otherAlbumsOnDevice.where((path) => path!.startsWith(volumePath)).map(trimVolumePath).toSet();
    final uniqueNameInVolume = unique(trimVolumePath(dirPath), otherAlbumsOnVolume);
-    final volume = androidFileUtils.getStorageVolume(dirPath);
+    final volume = androidFileUtils.getStorageVolume(dirPath)!;
    if (volume.isPrimary) {
      return uniqueNameInVolume;
    } else {
@ -72,7 +72,7 @@ mixin AlbumMixin on SourceBase {
    }
  }

-  Map<String, AvesEntry> getAlbumEntries() {
+  Map<String, AvesEntry?> getAlbumEntries() {
    final entries = sortedEntriesByDate;
    final regularAlbums = <String>[], appAlbums = <String>[], specialAlbums = <String>[];
    for (final album in rawAlbums) {
@ -90,7 +90,7 @@ mixin AlbumMixin on SourceBase {
    }
    return Map.fromEntries([...specialAlbums, ...appAlbums, ...regularAlbums].map((album) => MapEntry(
          album,
-          entries.firstWhere((entry) => entry.directory == album, orElse: () => null),
+          entries.firstWhereOrNull((entry) => entry.directory == album),
        )));
  }

@ -100,14 +100,14 @@ mixin AlbumMixin on SourceBase {
    cleanEmptyAlbums();
  }

-  void addDirectories(Set<String> albums) {
+  void addDirectories(Set<String?> albums) {
    if (!_directories.containsAll(albums)) {
      _directories.addAll(albums);
      _notifyAlbumChange();
    }
  }

-  void cleanEmptyAlbums([Set<String> albums]) {
+  void cleanEmptyAlbums([Set<String?>? albums]) {
    final emptyAlbums = (albums ?? _directories).where(_isEmptyAlbum).toSet();
    if (emptyAlbums.isNotEmpty) {
      _directories.removeAll(emptyAlbums);
@ -120,20 +120,20 @@ mixin AlbumMixin on SourceBase {
    }
  }

-  bool _isEmptyAlbum(String album) => !visibleEntries.any((entry) => entry.directory == album);
+  bool _isEmptyAlbum(String? album) => !visibleEntries.any((entry) => entry.directory == album);

  // filter summary

  // by directory
  final Map<String, int> _filterEntryCountMap = {};
-  final Map<String, AvesEntry> _filterRecentEntryMap = {};
+  final Map<String, AvesEntry?> _filterRecentEntryMap = {};

-  void invalidateAlbumFilterSummary({Set<AvesEntry> entries, Set<String> directories}) {
+  void invalidateAlbumFilterSummary({Set<AvesEntry>? entries, Set<String?>? directories}) {
    if (entries == null && directories == null) {
      _filterEntryCountMap.clear();
      _filterRecentEntryMap.clear();
    } else {
-      directories ??= entries.map((entry) => entry.directory).toSet();
+      directories ??= entries!.map((entry) => entry.directory).toSet();
      directories.forEach(_filterEntryCountMap.remove);
      directories.forEach(_filterRecentEntryMap.remove);
    }
@ -144,15 +144,15 @@ mixin AlbumMixin on SourceBase {
    return _filterEntryCountMap.putIfAbsent(filter.album, () => visibleEntries.where(filter.test).length);
  }

-  AvesEntry albumRecentEntry(AlbumFilter filter) {
-    return _filterRecentEntryMap.putIfAbsent(filter.album, () => sortedEntriesByDate.firstWhere(filter.test, orElse: () => null));
+  AvesEntry? albumRecentEntry(AlbumFilter filter) {
+    return _filterRecentEntryMap.putIfAbsent(filter.album, () => sortedEntriesByDate.firstWhereOrNull(filter.test));
  }
 }

 class AlbumsChangedEvent {}

 class AlbumSummaryInvalidatedEvent {
-  final Set<String> directories;
+  final Set<String?>? directories;

  const AlbumSummaryInvalidatedEvent(this.directories);
 }
--- a/lib/model/source/collection_lens.dart
+++ b/lib/model/source/collection_lens.dart
@ -2,7 +2,9 @@ import 'dart:async';
 import 'dart:collection';

 import 'package:aves/model/entry.dart';
+import 'package:aves/model/favourites.dart';
 import 'package:aves/model/filters/album.dart';
+import 'package:aves/model/filters/favourite.dart';
 import 'package:aves/model/filters/filters.dart';
 import 'package:aves/model/filters/location.dart';
 import 'package:aves/model/settings/settings.dart';
@ -22,22 +24,22 @@ class CollectionLens with ChangeNotifier, CollectionActivityMixin {
  EntryGroupFactor groupFactor;
  EntrySortFactor sortFactor;
  final AChangeNotifier filterChangeNotifier = AChangeNotifier(), sortGroupChangeNotifier = AChangeNotifier();
-  int id;
+  final List<StreamSubscription> _subscriptions = [];
+  int? id;
  bool listenToSource;

-  List<AvesEntry> _filteredSortedEntries;
-  List<StreamSubscription> _subscriptions = [];
+  List<AvesEntry> _filteredSortedEntries = [];

  Map<SectionKey, List<AvesEntry>> sections = Map.unmodifiable({});

  CollectionLens({
-    @required this.source,
-    Iterable<CollectionFilter> filters,
-    EntryGroupFactor groupFactor,
-    EntrySortFactor sortFactor,
+    required this.source,
+    Iterable<CollectionFilter?>? filters,
+    EntryGroupFactor? groupFactor,
+    EntrySortFactor? sortFactor,
    this.id,
    this.listenToSource = true,
-  })  : filters = {if (filters != null) ...filters.where((f) => f != null)},
+  })  : filters = (filters ?? {}).where((f) => f != null).cast<CollectionFilter>().toSet(),
        groupFactor = groupFactor ?? settings.collectionGroupFactor,
        sortFactor = sortFactor ?? settings.collectionSortFactor {
    id ??= hashCode;
@ -52,6 +54,7 @@ class CollectionLens with ChangeNotifier, CollectionActivityMixin {
          _refresh();
        }
      }));
+      favourites.addListener(onFavouritesChanged);
    }
    _refresh();
  }
@ -61,7 +64,7 @@ class CollectionLens with ChangeNotifier, CollectionActivityMixin {
    _subscriptions
      ..forEach((sub) => sub.cancel())
      ..clear();
-    _subscriptions = null;
+    favourites.removeListener(onFavouritesChanged);
    super.dispose();
  }

@ -70,11 +73,11 @@ class CollectionLens with ChangeNotifier, CollectionActivityMixin {
  int get entryCount => _filteredSortedEntries.length;

  // sorted as displayed to the user, i.e. sorted then grouped, not an absolute order on all entries
-  List<AvesEntry> _sortedEntries;
+  List<AvesEntry>? _sortedEntries;

  List<AvesEntry> get sortedEntries {
-    _sortedEntries ??= List.of(sections.entries.expand((e) => e.value));
-    return _sortedEntries;
+    _sortedEntries ??= List.of(sections.entries.expand((kv) => kv.value));
+    return _sortedEntries!;
  }

  bool get showHeaders {
@ -90,7 +93,7 @@ class CollectionLens with ChangeNotifier, CollectionActivityMixin {
  }

  void addFilter(CollectionFilter filter) {
-    if (filter == null || filters.contains(filter)) return;
+    if (filters.contains(filter)) return;
    if (filter.isUnique) {
      filters.removeWhere((old) => old.category == filter.category);
    }
@ -99,7 +102,7 @@ class CollectionLens with ChangeNotifier, CollectionActivityMixin {
  }

  void removeFilter(CollectionFilter filter) {
-    if (filter == null || !filters.contains(filter)) return;
+    if (!filters.contains(filter)) return;
    filters.remove(filter);
    onFilterChanged();
  }
@ -156,19 +159,19 @@ class CollectionLens with ChangeNotifier, CollectionActivityMixin {
            break;
          case EntryGroupFactor.none:
            sections = Map.fromEntries([
-              MapEntry(null, _filteredSortedEntries),
+              MapEntry(const SectionKey(), _filteredSortedEntries),
            ]);
            break;
        }
        break;
      case EntrySortFactor.size:
        sections = Map.fromEntries([
-          MapEntry(null, _filteredSortedEntries),
+          MapEntry(const SectionKey(), _filteredSortedEntries),
        ]);
        break;
      case EntrySortFactor.name:
        final byAlbum = groupBy<AvesEntry, EntryAlbumSectionKey>(_filteredSortedEntries, (entry) => EntryAlbumSectionKey(entry.directory));
-        sections = SplayTreeMap<EntryAlbumSectionKey, List<AvesEntry>>.of(byAlbum, (a, b) => source.compareAlbumsByName(a.directory, b.directory));
+        sections = SplayTreeMap<EntryAlbumSectionKey, List<AvesEntry>>.of(byAlbum, (a, b) => source.compareAlbumsByName(a.directory!, b.directory!));
        break;
    }
    sections = Map.unmodifiable(sections);
@ -184,7 +187,13 @@ class CollectionLens with ChangeNotifier, CollectionActivityMixin {
    _applyGroup();
  }

-  void onEntryAdded(Set<AvesEntry> entries) {
+  void onFavouritesChanged() {
+    if (filters.any((filter) => filter is FavouriteFilter)) {
+      _refresh();
+    }
+  }
+
+  void onEntryAdded(Set<AvesEntry>? entries) {
    _refresh();
  }

--- a/lib/model/source/collection_source.dart
+++ b/lib/model/source/collection_source.dart
@ -15,6 +15,7 @@ import 'package:aves/model/source/location.dart';
 import 'package:aves/model/source/tag.dart';
 import 'package:aves/services/image_op_events.dart';
 import 'package:aves/services/services.dart';
+import 'package:collection/collection.dart';
 import 'package:event_bus/event_bus.dart';
 import 'package:flutter/foundation.dart';

@ -31,7 +32,7 @@ mixin SourceBase {

  Stream<ProgressEvent> get progressStream => _progressStreamController.stream;

-  void setProgress({@required int done, @required int total}) => _progressStreamController.add(ProgressEvent(done: done, total: total));
+  void setProgress({required int done, required int total}) => _progressStreamController.add(ProgressEvent(done: done, total: total));
 }

 abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagMixin {
@ -45,24 +46,24 @@ abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagM
  // TODO TLAD use `Set.unmodifiable()` when possible
  Set<AvesEntry> get allEntries => Set.of(_rawEntries);

-  Set<AvesEntry> _visibleEntries;
+  Set<AvesEntry>? _visibleEntries;

  @override
  Set<AvesEntry> get visibleEntries {
    // TODO TLAD use `Set.unmodifiable()` when possible
    _visibleEntries ??= Set.of(_applyHiddenFilters(_rawEntries));
-    return _visibleEntries;
+    return _visibleEntries!;
  }

-  List<AvesEntry> _sortedEntriesByDate;
+  List<AvesEntry>? _sortedEntriesByDate;

  @override
  List<AvesEntry> get sortedEntriesByDate {
    _sortedEntriesByDate ??= List.unmodifiable(visibleEntries.toList()..sort(AvesEntry.compareByDate));
-    return _sortedEntriesByDate;
+    return _sortedEntriesByDate!;
  }

-  List<DateMetadata> _savedDates;
+  late List<DateMetadata> _savedDates;

  Future<void> loadDates() async {
    final stopwatch = Stopwatch()..start();
@ -75,7 +76,7 @@ abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagM
    return hiddenFilters.isEmpty ? entries : entries.where((entry) => !hiddenFilters.any((filter) => filter.test(entry)));
  }

-  void _invalidate([Set<AvesEntry> entries]) {
+  void _invalidate([Set<AvesEntry>? entries]) {
    _visibleEntries = null;
    _sortedEntriesByDate = null;
    invalidateAlbumFilterSummary(entries: entries);
@ -91,7 +92,7 @@ abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagM
    }
    entries.forEach((entry) {
      final contentId = entry.contentId;
-      entry.catalogDateMillis = _savedDates.firstWhere((metadata) => metadata.contentId == contentId, orElse: () => null)?.dateMillis;
+      entry.catalogDateMillis = _savedDates.firstWhereOrNull((metadata) => metadata.contentId == contentId)?.dateMillis;
    });
    _rawEntries.addAll(entries);
    _invalidate(entries);
@ -124,16 +125,16 @@ abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagM
  }

  Future<void> _moveEntry(AvesEntry entry, Map newFields) async {
-    final oldContentId = entry.contentId;
-    final newContentId = newFields['contentId'] as int;
+    final oldContentId = entry.contentId!;
+    final newContentId = newFields['contentId'] as int?;

    entry.contentId = newContentId;
    // `dateModifiedSecs` changes when moving entries to another directory,
    // but it does not change when renaming the containing directory
-    if (newFields.containsKey('dateModifiedSecs')) entry.dateModifiedSecs = newFields['dateModifiedSecs'] as int;
-    if (newFields.containsKey('path')) entry.path = newFields['path'] as String;
+    if (newFields.containsKey('dateModifiedSecs')) entry.dateModifiedSecs = newFields['dateModifiedSecs'] as int?;
+    if (newFields.containsKey('path')) entry.path = newFields['path'] as String?;
    if (newFields.containsKey('uri')) entry.uri = newFields['uri'] as String;
-    if (newFields.containsKey('title') != null) entry.sourceTitle = newFields['title'] as String;
+    if (newFields.containsKey('title')) entry.sourceTitle = newFields['title'] as String?;

    entry.catalogMetadata = entry.catalogMetadata?.copyWith(contentId: newContentId);
    entry.addressDetails = entry.addressDetails?.copyWith(contentId: newContentId);
@ -152,6 +153,7 @@ abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagM

    await _moveEntry(entry, newFields);
    entry.metadataChangeNotifier.notifyListeners();
+    eventBus.fire(EntryMovedEvent({entry}));
    return true;
  }

@ -159,7 +161,7 @@ abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagM
    final oldFilter = AlbumFilter(sourceAlbum, null);
    final pinned = settings.pinnedFilters.contains(oldFilter);
    final oldCoverContentId = covers.coverContentId(oldFilter);
-    final coverEntry = oldCoverContentId != null ? todoEntries.firstWhere((entry) => entry.contentId == oldCoverContentId, orElse: () => null) : null;
+    final coverEntry = oldCoverContentId != null ? todoEntries.firstWhereOrNull((entry) => entry.contentId == oldCoverContentId) : null;
    await updateAfterMove(
      todoEntries: todoEntries,
      copy: false,
@ -177,37 +179,39 @@ abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagM
  }

  Future<void> updateAfterMove({
-    @required Set<AvesEntry> todoEntries,
-    @required bool copy,
-    @required String destinationAlbum,
-    @required Set<MoveOpEvent> movedOps,
+    required Set<AvesEntry> todoEntries,
+    required bool copy,
+    required String destinationAlbum,
+    required Set<MoveOpEvent> movedOps,
  }) async {
    if (movedOps.isEmpty) return;

-    final fromAlbums = <String>{};
+    final fromAlbums = <String?>{};
    final movedEntries = <AvesEntry>{};
    if (copy) {
      movedOps.forEach((movedOp) {
        final sourceUri = movedOp.uri;
        final newFields = movedOp.newFields;
-        final sourceEntry = todoEntries.firstWhere((entry) => entry.uri == sourceUri, orElse: () => null);
-        fromAlbums.add(sourceEntry.directory);
-        movedEntries.add(sourceEntry?.copyWith(
-          uri: newFields['uri'] as String,
-          path: newFields['path'] as String,
-          contentId: newFields['contentId'] as int,
-          dateModifiedSecs: newFields['dateModifiedSecs'] as int,
-        ));
+        final sourceEntry = todoEntries.firstWhereOrNull((entry) => entry.uri == sourceUri);
+        if (sourceEntry != null) {
+          fromAlbums.add(sourceEntry.directory);
+          movedEntries.add(sourceEntry.copyWith(
+            uri: newFields['uri'] as String?,
+            path: newFields['path'] as String?,
+            contentId: newFields['contentId'] as int?,
+            dateModifiedSecs: newFields['dateModifiedSecs'] as int?,
+          ));
+        }
      });
      await metadataDb.saveEntries(movedEntries);
-      await metadataDb.saveMetadata(movedEntries.map((entry) => entry.catalogMetadata));
-      await metadataDb.saveAddresses(movedEntries.map((entry) => entry.addressDetails));
+      await metadataDb.saveMetadata(movedEntries.map((entry) => entry.catalogMetadata).where((v) => v != null).cast<CatalogMetadata>().toSet());
+      await metadataDb.saveAddresses(movedEntries.map((entry) => entry.addressDetails).where((v) => v != null).cast<AddressDetails>().toSet());
    } else {
      await Future.forEach<MoveOpEvent>(movedOps, (movedOp) async {
        final newFields = movedOp.newFields;
        if (newFields.isNotEmpty) {
          final sourceUri = movedOp.uri;
-          final entry = todoEntries.firstWhere((entry) => entry.uri == sourceUri, orElse: () => null);
+          final entry = todoEntries.firstWhereOrNull((entry) => entry.uri == sourceUri);
          if (entry != null) {
            fromAlbums.add(entry.directory);
            movedEntries.add(entry);
@ -255,17 +259,17 @@ abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagM
    return 0;
  }

-  AvesEntry recentEntry(CollectionFilter filter) {
+  AvesEntry? recentEntry(CollectionFilter filter) {
    if (filter is AlbumFilter) return albumRecentEntry(filter);
    if (filter is LocationFilter) return countryRecentEntry(filter);
    if (filter is TagFilter) return tagRecentEntry(filter);
    return null;
  }

-  AvesEntry coverEntry(CollectionFilter filter) {
+  AvesEntry? coverEntry(CollectionFilter filter) {
    final contentId = covers.coverContentId(filter);
    if (contentId != null) {
-      final entry = visibleEntries.firstWhere((entry) => entry.contentId == contentId, orElse: () => null);
+      final entry = visibleEntries.firstWhereOrNull((entry) => entry.contentId == contentId);
      if (entry != null) return entry;
    }
    return recentEntry(filter);
@ -297,7 +301,7 @@ abstract class CollectionSource with SourceBase, AlbumMixin, LocationMixin, TagM
 }

 class EntryAddedEvent {
-  final Set<AvesEntry> entries;
+  final Set<AvesEntry>? entries;

  const EntryAddedEvent([this.entries]);
 }
@ -309,7 +313,7 @@ class EntryRemovedEvent {
 }

 class EntryMovedEvent {
-  final Iterable<AvesEntry> entries;
+  final Set<AvesEntry> entries;

  const EntryMovedEvent(this.entries);
 }
@ -324,5 +328,5 @@ class FilterVisibilityChangedEvent {
 class ProgressEvent {
  final int done, total;

-  const ProgressEvent({@required this.done, @required this.total});
+  const ProgressEvent({required this.done, required this.total});
 }
--- a/lib/model/source/location.dart
+++ b/lib/model/source/location.dart
@ -22,7 +22,7 @@ mixin LocationMixin on SourceBase {
    final saved = await metadataDb.loadAddresses();
    visibleEntries.forEach((entry) {
      final contentId = entry.contentId;
-      entry.addressDetails = saved.firstWhere((address) => address.contentId == contentId, orElse: () => null);
+      entry.addressDetails = saved.firstWhereOrNull((address) => address.contentId == contentId);
    });
    debugPrint('$runtimeType loadAddresses complete in ${stopwatch.elapsed.inMilliseconds}ms for ${saved.length} entries');
    onAddressMetadataChanged();
@ -44,19 +44,19 @@ mixin LocationMixin on SourceBase {
    setProgress(done: progressDone, total: progressTotal);

    // final stopwatch = Stopwatch()..start();
-    final countryCodeMap = await countryTopology.countryCodeMap(todo.map((entry) => entry.latLng).toSet());
+    final countryCodeMap = await countryTopology.countryCodeMap(todo.map((entry) => entry.latLng!).toSet());
    final newAddresses = <AddressDetails>[];
    todo.forEach((entry) {
      final position = entry.latLng;
-      final countryCode = countryCodeMap.entries.firstWhere((kv) => kv.value.contains(position), orElse: () => null)?.key;
+      final countryCode = countryCodeMap.entries.firstWhereOrNull((kv) => kv.value.contains(position))?.key;
      entry.setCountry(countryCode);
      if (entry.hasAddress) {
-        newAddresses.add(entry.addressDetails);
+        newAddresses.add(entry.addressDetails!);
      }
      setProgress(done: ++progressDone, total: progressTotal);
    });
    if (newAddresses.isNotEmpty) {
-      await metadataDb.saveAddresses(List.unmodifiable(newAddresses));
+      await metadataDb.saveAddresses(Set.of(newAddresses));
      onAddressMetadataChanged();
    }
    // debugPrint('$runtimeType _locateCountries complete in ${stopwatch.elapsed.inMilliseconds}ms');
@ -82,14 +82,16 @@ mixin LocationMixin on SourceBase {
    // cf https://en.wikipedia.org/wiki/Decimal_degrees#Precision
    final latLngFactor = pow(10, 2);
    Tuple2<int, int> approximateLatLng(AvesEntry entry) {
-      final lat = entry.catalogMetadata?.latitude;
-      final lng = entry.catalogMetadata?.longitude;
-      if (lat == null || lng == null) return null;
+      // entry has coordinates
+      final lat = entry.catalogMetadata!.latitude!;
+      final lng = entry.catalogMetadata!.longitude!;
      return Tuple2<int, int>((lat * latLngFactor).round(), (lng * latLngFactor).round());
    }

-    final knownLocations = <Tuple2<int, int>, AddressDetails>{};
-    byLocated[true]?.forEach((entry) => knownLocations.putIfAbsent(approximateLatLng(entry), () => entry.addressDetails));
+    final knownLocations = <Tuple2<int, int>, AddressDetails?>{};
+    byLocated[true]?.forEach((entry) {
+      knownLocations.putIfAbsent(approximateLatLng(entry), () => entry.addressDetails);
+    });

    stateNotifier.value = SourceState.locating;
    var progressDone = 0;
@ -108,9 +110,9 @@ mixin LocationMixin on SourceBase {
        knownLocations[latLng] = entry.addressDetails;
      }
      if (entry.hasFineAddress) {
-        newAddresses.add(entry.addressDetails);
+        newAddresses.add(entry.addressDetails!);
        if (newAddresses.length >= _commitCountThreshold) {
-          await metadataDb.saveAddresses(List.unmodifiable(newAddresses));
+          await metadataDb.saveAddresses(Set.of(newAddresses));
          onAddressMetadataChanged();
          newAddresses.clear();
        }
@ -118,7 +120,7 @@ mixin LocationMixin on SourceBase {
      setProgress(done: ++progressDone, total: progressTotal);
    });
    if (newAddresses.isNotEmpty) {
-      await metadataDb.saveAddresses(List.unmodifiable(newAddresses));
+      await metadataDb.saveAddresses(Set.of(newAddresses));
      onAddressMetadataChanged();
    }
    // debugPrint('$runtimeType _locatePlaces complete in ${stopwatch.elapsed.inSeconds}s');
@ -130,8 +132,8 @@ mixin LocationMixin on SourceBase {
  }

  void updateLocations() {
-    final locations = visibleEntries.where((entry) => entry.hasAddress).map((entry) => entry.addressDetails).toList();
-    final updatedPlaces = locations.map((address) => address.place).where((s) => s != null && s.isNotEmpty).toSet().toList()..sort(compareAsciiUpperCase);
+    final locations = visibleEntries.where((entry) => entry.hasAddress).map((entry) => entry.addressDetails).cast<AddressDetails>().toList();
+    final updatedPlaces = locations.map((address) => address.place).where((s) => s != null && s.isNotEmpty).toSet().toList()..sort(compareAsciiUpperCase as int Function(String?, String?)?);
    if (!listEquals(updatedPlaces, sortedPlaces)) {
      sortedPlaces = List.unmodifiable(updatedPlaces);
      eventBus.fire(PlacesChangedEvent());
@ -140,7 +142,7 @@ mixin LocationMixin on SourceBase {
    // the same country code could be found with different country names
    // e.g. if the locale changed between geocoding calls
    // so we merge countries by code, keeping only one name for each code
-    final countriesByCode = Map.fromEntries(locations.map((address) => MapEntry(address.countryCode, address.countryName)).where((kv) => kv.key != null && kv.key.isNotEmpty));
+    final countriesByCode = Map.fromEntries(locations.map((address) => MapEntry(address.countryCode, address.countryName)).where((kv) => kv.key != null && kv.key!.isNotEmpty));
    final updatedCountries = countriesByCode.entries.map((kv) => '${kv.value}${LocationFilter.locationSeparator}${kv.key}').toList()..sort(compareAsciiUpperCase);
    if (!listEquals(updatedCountries, sortedCountries)) {
      sortedCountries = List.unmodifiable(updatedCountries);
@ -153,27 +155,30 @@ mixin LocationMixin on SourceBase {

  // by country code
  final Map<String, int> _filterEntryCountMap = {};
-  final Map<String, AvesEntry> _filterRecentEntryMap = {};
+  final Map<String, AvesEntry?> _filterRecentEntryMap = {};

-  void invalidateCountryFilterSummary([Set<AvesEntry> entries]) {
-    Set<String> countryCodes;
+  void invalidateCountryFilterSummary([Set<AvesEntry>? entries]) {
+    Set<String>? countryCodes;
    if (entries == null) {
      _filterEntryCountMap.clear();
      _filterRecentEntryMap.clear();
    } else {
-      countryCodes = entries.where((entry) => entry.hasAddress).map((entry) => entry.addressDetails.countryCode).toSet();
-      countryCodes.remove(null);
+      countryCodes = entries.where((entry) => entry.hasAddress).map((entry) => entry.addressDetails!.countryCode).where((v) => v != null).cast<String>().toSet();
      countryCodes.forEach(_filterEntryCountMap.remove);
    }
    eventBus.fire(CountrySummaryInvalidatedEvent(countryCodes));
  }

  int countryEntryCount(LocationFilter filter) {
-    return _filterEntryCountMap.putIfAbsent(filter.countryCode, () => visibleEntries.where(filter.test).length);
+    final countryCode = filter.countryCode;
+    if (countryCode == null) return 0;
+    return _filterEntryCountMap.putIfAbsent(countryCode, () => visibleEntries.where(filter.test).length);
  }

-  AvesEntry countryRecentEntry(LocationFilter filter) {
-    return _filterRecentEntryMap.putIfAbsent(filter.countryCode, () => sortedEntriesByDate.firstWhere(filter.test, orElse: () => null));
+  AvesEntry? countryRecentEntry(LocationFilter filter) {
+    final countryCode = filter.countryCode;
+    if (countryCode == null) return null;
+    return _filterRecentEntryMap.putIfAbsent(countryCode, () => sortedEntriesByDate.firstWhereOrNull(filter.test));
  }
 }

@ -184,7 +189,7 @@ class PlacesChangedEvent {}
 class CountriesChangedEvent {}

 class CountrySummaryInvalidatedEvent {
-  final Set<String> countryCodes;
+  final Set<String>? countryCodes;

  const CountrySummaryInvalidatedEvent(this.countryCodes);
 }
--- a/lib/model/source/media_store_source.dart
+++ b/lib/model/source/media_store_source.dart
@ -10,6 +10,7 @@ import 'package:aves/model/source/enums.dart';
 import 'package:aves/services/services.dart';
 import 'package:aves/utils/android_file_utils.dart';
 import 'package:aves/utils/math_utils.dart';
+import 'package:collection/collection.dart';
 import 'package:firebase_analytics/firebase_analytics.dart';
 import 'package:flutter/material.dart';

@ -27,13 +28,15 @@ class MediaStoreSource extends CollectionSource {
    await favourites.init();
    await covers.init();
    final currentTimeZone = await timeService.getDefaultTimeZone();
-    final catalogTimeZone = settings.catalogTimeZone;
-    if (currentTimeZone != catalogTimeZone) {
-      // clear catalog metadata to get correct date/times when moving to a different time zone
-      debugPrint('$runtimeType clear catalog metadata to get correct date/times');
-      await metadataDb.clearDates();
-      await metadataDb.clearMetadataEntries();
-      settings.catalogTimeZone = currentTimeZone;
+    if (currentTimeZone != null) {
+      final catalogTimeZone = settings.catalogTimeZone;
+      if (currentTimeZone != catalogTimeZone) {
+        // clear catalog metadata to get correct date/times when moving to a different time zone
+        debugPrint('$runtimeType clear catalog metadata to get correct date/times');
+        await metadataDb.clearDates();
+        await metadataDb.clearMetadataEntries();
+        settings.catalogTimeZone = currentTimeZone;
+      }
    }
    await loadDates(); // 100ms for 5400 entries
    _initialized = true;
@ -49,7 +52,7 @@ class MediaStoreSource extends CollectionSource {
    clearEntries();

    final oldEntries = await metadataDb.loadEntries(); // 400ms for 5500 entries
-    final knownDateById = Map.fromEntries(oldEntries.map((entry) => MapEntry(entry.contentId, entry.dateModifiedSecs)));
+    final knownDateById = Map.fromEntries(oldEntries.map((entry) => MapEntry(entry.contentId!, entry.dateModifiedSecs!)));
    final obsoleteContentIds = (await mediaStoreService.checkObsoleteContentIds(knownDateById.keys.toList())).toSet();
    oldEntries.removeWhere((entry) => obsoleteContentIds.contains(entry.contentId));

@ -63,7 +66,7 @@ class MediaStoreSource extends CollectionSource {
    await metadataDb.removeIds(obsoleteContentIds, metadataOnly: false);

    // verify paths because some apps move files without updating their `last modified date`
-    final knownPathById = Map.fromEntries(allEntries.map((entry) => MapEntry(entry.contentId, entry.path)));
+    final knownPathById = Map.fromEntries(allEntries.map((entry) => MapEntry(entry.contentId!, entry.path)));
    final movedContentIds = (await mediaStoreService.checkObsoletePaths(knownPathById)).toSet();
    movedContentIds.forEach((contentId) {
      // make obsolete by resetting its modified date
@ -130,20 +133,22 @@ class MediaStoreSource extends CollectionSource {
  Future<Set<String>> refreshUris(Set<String> changedUris) async {
    if (!_initialized || !isMonitoring) return changedUris;

-    final uriByContentId = Map.fromEntries(changedUris.map((uri) {
-      if (uri == null) return null;
-      final pathSegments = Uri.parse(uri).pathSegments;
-      // e.g. URI `content://media/` has no path segment
-      if (pathSegments.isEmpty) return null;
-      final idString = pathSegments.last;
-      final contentId = int.tryParse(idString);
-      if (contentId == null) return null;
-      return MapEntry(contentId, uri);
-    }).where((kv) => kv != null));
+    final uriByContentId = Map.fromEntries(changedUris
+        .map((uri) {
+          final pathSegments = Uri.parse(uri).pathSegments;
+          // e.g. URI `content://media/` has no path segment
+          if (pathSegments.isEmpty) return null;
+          final idString = pathSegments.last;
+          final contentId = int.tryParse(idString);
+          if (contentId == null) return null;
+          return MapEntry(contentId, uri);
+        })
+        .where((kv) => kv != null)
+        .cast<MapEntry<int, String>>());

    // clean up obsolete entries
    final obsoleteContentIds = (await mediaStoreService.checkObsoleteContentIds(uriByContentId.keys.toList())).toSet();
-    final obsoleteUris = obsoleteContentIds.map((contentId) => uriByContentId[contentId]).toSet();
+    final obsoleteUris = obsoleteContentIds.map((contentId) => uriByContentId[contentId]).where((v) => v != null).cast<String>().toSet();
    await removeEntries(obsoleteUris);
    obsoleteContentIds.forEach(uriByContentId.remove);

@ -156,14 +161,16 @@ class MediaStoreSource extends CollectionSource {
      final uri = kv.value;
      final sourceEntry = await imageFileService.getEntry(uri, null);
      if (sourceEntry != null) {
-        final existingEntry = allEntries.firstWhere((entry) => entry.contentId == contentId, orElse: () => null);
+        final existingEntry = allEntries.firstWhereOrNull((entry) => entry.contentId == contentId);
        // compare paths because some apps move files without updating their `last modified date`
-        if (existingEntry == null || sourceEntry.dateModifiedSecs > existingEntry.dateModifiedSecs || sourceEntry.path != existingEntry.path) {
-          final volume = androidFileUtils.getStorageVolume(sourceEntry.path);
+        if (existingEntry == null || (sourceEntry.dateModifiedSecs ?? 0) > (existingEntry.dateModifiedSecs ?? 0) || sourceEntry.path != existingEntry.path) {
+          final newPath = sourceEntry.path;
+          final volume = newPath != null ? androidFileUtils.getStorageVolume(newPath) : null;
          if (volume != null) {
            newEntries.add(sourceEntry);
-            if (existingEntry != null) {
-              existingDirectories.add(existingEntry.directory);
+            final existingDirectory = existingEntry?.directory;
+            if (existingDirectory != null) {
+              existingDirectories.add(existingDirectory);
            }
          } else {
            debugPrint('$runtimeType refreshUris entry=$sourceEntry is not located on a known storage volume. Will retry soon...');
@ -189,7 +196,7 @@ class MediaStoreSource extends CollectionSource {
  @override
  Future<void> refreshMetadata(Set<AvesEntry> entries) {
    final contentIds = entries.map((entry) => entry.contentId).toSet();
-    metadataDb.removeIds(contentIds, metadataOnly: true);
+    metadataDb.removeIds(contentIds as Set<int>, metadataOnly: true);
    return refresh();
  }
 }
--- a/lib/model/source/section_keys.dart
+++ b/lib/model/source/section_keys.dart
@ -5,7 +5,7 @@ class SectionKey {
 }

 class EntryAlbumSectionKey extends SectionKey {
-  final String directory;
+  final String? directory;

  const EntryAlbumSectionKey(this.directory);

@ -23,7 +23,7 @@ class EntryAlbumSectionKey extends SectionKey {
 }

 class EntryDateSectionKey extends SectionKey {
-  final DateTime date;
+  final DateTime? date;

  const EntryDateSectionKey(this.date);

--- a/lib/model/source/tag.dart
+++ b/lib/model/source/tag.dart
@ -17,7 +17,7 @@ mixin TagMixin on SourceBase {
    final saved = await metadataDb.loadMetadataEntries();
    visibleEntries.forEach((entry) {
      final contentId = entry.contentId;
-      entry.catalogMetadata = saved.firstWhere((metadata) => metadata.contentId == contentId, orElse: () => null);
+      entry.catalogMetadata = saved.firstWhereOrNull((metadata) => metadata.contentId == contentId);
    });
    debugPrint('$runtimeType loadCatalogMetadata complete in ${stopwatch.elapsed.inMilliseconds}ms for ${saved.length} entries');
    onCatalogMetadataChanged();
@ -37,16 +37,16 @@ mixin TagMixin on SourceBase {
    await Future.forEach<AvesEntry>(todo, (entry) async {
      await entry.catalog(background: true);
      if (entry.isCatalogued) {
-        newMetadata.add(entry.catalogMetadata);
+        newMetadata.add(entry.catalogMetadata!);
        if (newMetadata.length >= _commitCountThreshold) {
-          await metadataDb.saveMetadata(List.unmodifiable(newMetadata));
+          await metadataDb.saveMetadata(Set.of(newMetadata));
          onCatalogMetadataChanged();
          newMetadata.clear();
        }
      }
      setProgress(done: ++progressDone, total: progressTotal);
    });
-    await metadataDb.saveMetadata(List.unmodifiable(newMetadata));
+    await metadataDb.saveMetadata(Set.of(newMetadata));
    onCatalogMetadataChanged();
 //    debugPrint('$runtimeType catalogEntries complete in ${stopwatch.elapsed.inSeconds}s');
  }
@ -69,10 +69,10 @@ mixin TagMixin on SourceBase {

  // by tag
  final Map<String, int> _filterEntryCountMap = {};
-  final Map<String, AvesEntry> _filterRecentEntryMap = {};
+  final Map<String, AvesEntry?> _filterRecentEntryMap = {};

-  void invalidateTagFilterSummary([Set<AvesEntry> entries]) {
-    Set<String> tags;
+  void invalidateTagFilterSummary([Set<AvesEntry>? entries]) {
+    Set<String>? tags;
    if (entries == null) {
      _filterEntryCountMap.clear();
      _filterRecentEntryMap.clear();
@ -87,8 +87,8 @@ mixin TagMixin on SourceBase {
    return _filterEntryCountMap.putIfAbsent(filter.tag, () => visibleEntries.where(filter.test).length);
  }

-  AvesEntry tagRecentEntry(TagFilter filter) {
-    return _filterRecentEntryMap.putIfAbsent(filter.tag, () => sortedEntriesByDate.firstWhere(filter.test, orElse: () => null));
+  AvesEntry? tagRecentEntry(TagFilter filter) {
+    return _filterRecentEntryMap.putIfAbsent(filter.tag, () => sortedEntriesByDate.firstWhereOrNull(filter.test));
  }
 }

@ -97,7 +97,7 @@ class CatalogMetadataChangedEvent {}
 class TagsChangedEvent {}

 class TagSummaryInvalidatedEvent {
-  final Set<String> tags;
+  final Set<String>? tags;

  const TagSummaryInvalidatedEvent(this.tags);
 }
--- a/lib/model/video/metadata.dart
+++ b/lib/model/video/metadata.dart
@ -11,6 +11,8 @@ import 'package:aves/utils/math_utils.dart';
 import 'package:aves/utils/string_utils.dart';
 import 'package:aves/utils/time_utils.dart';
 import 'package:aves/widgets/viewer/video/fijkplayer.dart';
+import 'package:collection/collection.dart';
+// ignore: import_of_legacy_library_into_null_safe
 import 'package:fijkplayer/fijkplayer.dart';
 import 'package:flutter/foundation.dart';

@ -54,16 +56,16 @@ class VideoMetadataFormatter {
      final value = kv.value;
      if (value != null) {
        try {
-          String key;
-          String keyLanguage;
+          String? key;
+          String? keyLanguage;
          // some keys have a language suffix, but they may be duplicates
          // we only keep the root key when they have the same value as the same key with no language
          final languageMatch = keyWithLanguagePattern.firstMatch(kv.key);
          if (languageMatch != null) {
-            final code = languageMatch.group(2);
+            final code = languageMatch.group(2)!;
            final native = _formatLanguage(code);
            if (native != code) {
-              final root = languageMatch.group(1);
+              final root = languageMatch.group(1)!;
              final rootValue = info[root];
              // skip if it is a duplicate of the same entry with no language
              if (rootValue == value) continue;
@ -76,7 +78,7 @@ class VideoMetadataFormatter {
          }
          key = (key ?? (kv.key as String)).toLowerCase();

-          void save(String key, String value) {
+          void save(String key, String? value) {
            if (value != null) {
              dir[keyLanguage != null ? '$key ($keyLanguage)' : key] = value;
            }
@ -129,21 +131,26 @@ class VideoMetadataFormatter {
            case Keys.codecProfileId:
              if (codec == 'h264') {
                final profile = int.tryParse(value);
-                if (profile != null && profile != 0) {
-                  final level = int.tryParse(info[Keys.codecLevel]);
+                final levelString = info[Keys.codecLevel];
+                if (profile != null && profile != 0 && levelString != null) {
+                  final level = int.tryParse(levelString) ?? 0;
                  save('Codec Profile', H264.formatProfile(profile, level));
                }
              }
              break;
            case Keys.compatibleBrands:
-              save('Compatible Brands', RegExp(r'.{4}').allMatches(value).map((m) => _formatBrand(m.group(0))).join(', '));
+              final formattedBrands = RegExp(r'.{4}').allMatches(value).map((m) {
+                final brand = m.group(0)!;
+                return _formatBrand(brand);
+              }).join(', ');
+              save('Compatible Brands', formattedBrands);
              break;
            case Keys.creationTime:
              save('Creation Time', _formatDate(value));
              break;
            case Keys.date:
-              if (value != '0') {
-                final charCount = (value as String)?.length ?? 0;
+              if (value is String && value != '0') {
+                final charCount = value.length;
                save(charCount == 4 ? 'Year' : 'Date', value);
              }
              break;
@ -222,10 +229,10 @@ class VideoMetadataFormatter {

  static String _formatChannelLayout(value) => ChannelLayouts.names[value] ?? 'unknown ($value)';

-  static String _formatCodecName(String value) => _codecNames[value] ?? value?.toUpperCase()?.replaceAll('_', ' ');
+  static String _formatCodecName(String value) => _codecNames[value] ?? value.toUpperCase().replaceAll('_', ' ');

  // input example: '2021-04-12T09:14:37.000000Z'
-  static String _formatDate(String value) {
+  static String? _formatDate(String value) {
    final date = DateTime.tryParse(value);
    if (date == null) return value;
    if (date == _epoch) return null;
@ -236,10 +243,10 @@ class VideoMetadataFormatter {
  static String _formatDuration(String value) {
    final match = _durationPattern.firstMatch(value);
    if (match != null) {
-      final h = int.tryParse(match.group(1));
-      final m = int.tryParse(match.group(2));
-      final s = int.tryParse(match.group(3));
-      final millis = double.tryParse(match.group(4));
+      final h = int.tryParse(match.group(1)!);
+      final m = int.tryParse(match.group(2)!);
+      final s = int.tryParse(match.group(3)!);
+      final millis = double.tryParse(match.group(4)!);
      if (h != null && m != null && s != null && millis != null) {
        return formatPreciseDuration(Duration(
          hours: h,
@ -258,15 +265,15 @@ class VideoMetadataFormatter {
  }

  static String _formatLanguage(String value) {
-    final language = Language.living639_2.firstWhere((language) => language.iso639_2 == value, orElse: () => null);
+    final language = Language.living639_2.firstWhereOrNull((language) => language.iso639_2 == value);
    return language?.native ?? value;
  }

  // format ISO 6709 input, e.g. '+37.5090+127.0243/' (Samsung), '+51.3328-000.7053+113.474/' (Apple)
-  static String _formatLocation(String value) {
+  static String? _formatLocation(String value) {
    final matches = _locationPattern.allMatches(value);
    if (matches.isNotEmpty) {
-      final coordinates = matches.map((m) => double.tryParse(m.group(0))).toList();
+      final coordinates = matches.map((m) => double.tryParse(m.group(0)!)).toList();
      if (coordinates.every((c) => c == 0)) return null;
      return coordinates.join(', ');
    }
--- a/lib/ref/brand_colors.dart
+++ b/lib/ref/brand_colors.dart
@ -7,17 +7,15 @@ class BrandColors {
  static const Color android = Color(0xFF3DDC84);
  static const Color flutter = Color(0xFF47D1FD);

-  static Color get(String text) {
-    if (text != null) {
-      switch (text.toLowerCase()) {
-        case 'after effects':
-          return adobeAfterEffects;
-        case 'illustrator':
-          return adobeIllustrator;
-        case 'photoshop':
-        case 'lightroom':
-          return adobePhotoshop;
-      }
+  static Color? get(String text) {
+    switch (text.toLowerCase()) {
+      case 'after effects':
+        return adobeAfterEffects;
+      case 'illustrator':
+        return adobeIllustrator;
+      case 'photoshop':
+      case 'lightroom':
+        return adobePhotoshop;
    }
    return null;
  }
--- a/lib/ref/exif.dart
+++ b/lib/ref/exif.dart
@ -133,7 +133,7 @@ class Exif {
  }

  static String getExifVersionDescription(String valueString) {
-    if (valueString?.length == 4) {
+    if (valueString.length == 4) {
      final major = int.tryParse(valueString.substring(0, 2));
      final minor = int.tryParse(valueString.substring(2, 4));
      if (major != null && minor != null) {
--- a/lib/ref/languages.dart
+++ b/lib/ref/languages.dart
@ -1,9 +1,10 @@
 class Language {
-  final String iso639_2, name, native;
+  final String iso639_2, name;
+  final String? native;

  const Language({
-    this.iso639_2,
-    this.name,
+    required this.iso639_2,
+    required this.name,
    this.native,
  });

--- a/lib/services/android_app_service.dart
+++ b/lib/services/android_app_service.dart
@ -14,7 +14,7 @@ class AndroidAppService {
      final result = await platform.invokeMethod('getPackages');
      final packages = (result as List).cast<Map>().map((map) => Package.fromMap(map)).toSet();
      // additional info for known directories
-      final kakaoTalk = packages.firstWhere((package) => package.packageName == 'com.kakao.talk', orElse: () => null);
+      final kakaoTalk = packages.firstWhereOrNull((package) => package.packageName == 'com.kakao.talk');
      if (kakaoTalk != null) {
        kakaoTalk.ownedDirs.add('KakaoTalkDownload');
      }
@ -31,19 +31,20 @@ class AndroidAppService {
        'packageName': packageName,
        'sizeDip': size,
      });
-      return result as Uint8List;
+      if (result != null) return result as Uint8List;
    } on PlatformException catch (e) {
      debugPrint('getAppIcon failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
-    return null;
+    return Uint8List(0);
  }

  static Future<bool> edit(String uri, String mimeType) async {
    try {
-      return await platform.invokeMethod('edit', <String, dynamic>{
+      final result = await platform.invokeMethod('edit', <String, dynamic>{
        'uri': uri,
        'mimeType': mimeType,
      });
+      if (result != null) return result as bool;
    } on PlatformException catch (e) {
      debugPrint('edit failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -52,10 +53,11 @@ class AndroidAppService {

  static Future<bool> open(String uri, String mimeType) async {
    try {
-      return await platform.invokeMethod('open', <String, dynamic>{
+      final result = await platform.invokeMethod('open', <String, dynamic>{
        'uri': uri,
        'mimeType': mimeType,
      });
+      if (result != null) return result as bool;
    } on PlatformException catch (e) {
      debugPrint('open failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -64,9 +66,10 @@ class AndroidAppService {

  static Future<bool> openMap(String geoUri) async {
    try {
-      return await platform.invokeMethod('openMap', <String, dynamic>{
+      final result = await platform.invokeMethod('openMap', <String, dynamic>{
        'geoUri': geoUri,
      });
+      if (result != null) return result as bool;
    } on PlatformException catch (e) {
      debugPrint('openMap failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -75,10 +78,11 @@ class AndroidAppService {

  static Future<bool> setAs(String uri, String mimeType) async {
    try {
-      return await platform.invokeMethod('setAs', <String, dynamic>{
+      final result = await platform.invokeMethod('setAs', <String, dynamic>{
        'uri': uri,
        'mimeType': mimeType,
      });
+      if (result != null) return result as bool;
    } on PlatformException catch (e) {
      debugPrint('setAs failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -90,9 +94,10 @@ class AndroidAppService {
    // e.g. Google Lens declares receiving "image/jpeg" only, but it can actually handle more formats
    final urisByMimeType = groupBy<AvesEntry, String>(entries, (e) => e.mimeTypeAnySubtype).map((k, v) => MapEntry(k, v.map((e) => e.uri).toList()));
    try {
-      return await platform.invokeMethod('share', <String, dynamic>{
+      final result = await platform.invokeMethod('share', <String, dynamic>{
        'urisByMimeType': urisByMimeType,
      });
+      if (result != null) return result as bool;
    } on PlatformException catch (e) {
      debugPrint('shareEntries failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -101,11 +106,12 @@ class AndroidAppService {

  static Future<bool> shareSingle(String uri, String mimeType) async {
    try {
-      return await platform.invokeMethod('share', <String, dynamic>{
+      final result = await platform.invokeMethod('share', <String, dynamic>{
        'urisByMimeType': {
          mimeType: [uri]
        },
      });
+      if (result != null) return result as bool;
    } on PlatformException catch (e) {
      debugPrint('shareSingle failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
--- a/lib/services/android_debug_service.dart
+++ b/lib/services/android_debug_service.dart
@ -9,7 +9,7 @@ class AndroidDebugService {
  static Future<Map> getContextDirs() async {
    try {
      final result = await platform.invokeMethod('getContextDirs');
-      return result as Map;
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('getContextDirs failed with code=${e.code}, exception=${e.message}, details=${e.details}}');
    }
@ -19,7 +19,7 @@ class AndroidDebugService {
  static Future<Map> getEnv() async {
    try {
      final result = await platform.invokeMethod('getEnv');
-      return result as Map;
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('getEnv failed with code=${e.code}, exception=${e.message}, details=${e.details}}');
    }
@ -31,8 +31,8 @@ class AndroidDebugService {
      // returns map with all data available when decoding image bounds with `BitmapFactory`
      final result = await platform.invokeMethod('getBitmapFactoryInfo', <String, dynamic>{
        'uri': entry.uri,
-      }) as Map;
-      return result;
+      });
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('getBitmapFactoryInfo failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -45,8 +45,8 @@ class AndroidDebugService {
      final result = await platform.invokeMethod('getContentResolverMetadata', <String, dynamic>{
        'mimeType': entry.mimeType,
        'uri': entry.uri,
-      }) as Map;
-      return result;
+      });
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('getContentResolverMetadata failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -60,8 +60,8 @@ class AndroidDebugService {
        'mimeType': entry.mimeType,
        'uri': entry.uri,
        'sizeBytes': entry.sizeBytes,
-      }) as Map;
-      return result;
+      });
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('getExifInterfaceMetadata failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -73,8 +73,8 @@ class AndroidDebugService {
      // returns map with all data available from `MediaMetadataRetriever`
      final result = await platform.invokeMethod('getMediaMetadataRetrieverMetadata', <String, dynamic>{
        'uri': entry.uri,
-      }) as Map;
-      return result;
+      });
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('getMediaMetadataRetrieverMetadata failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -88,8 +88,8 @@ class AndroidDebugService {
        'mimeType': entry.mimeType,
        'uri': entry.uri,
        'sizeBytes': entry.sizeBytes,
-      }) as Map;
-      return result;
+      });
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('getMetadataExtractorSummary failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -102,8 +102,8 @@ class AndroidDebugService {
    try {
      final result = await platform.invokeMethod('getTiffStructure', <String, dynamic>{
        'uri': entry.uri,
-      }) as Map;
-      return result;
+      });
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('getTiffStructure failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
--- a/lib/services/app_shortcut_service.dart
+++ b/lib/services/app_shortcut_service.dart
@ -10,24 +10,27 @@ class AppShortcutService {
  static const platform = MethodChannel('deckers.thibault/aves/shortcut');

  // this ability will not change over the lifetime of the app
-  static bool _canPin;
+  static bool? _canPin;

-  static Future<bool> canPin() async {
+  static Future<bool > canPin() async {
    if (_canPin != null) {
-      return SynchronousFuture(_canPin);
+      return SynchronousFuture(_canPin!);
    }

    try {
-      _canPin = await platform.invokeMethod('canPin');
-      return _canPin;
+      final result = await platform.invokeMethod('canPin');
+      if (result != null) {
+        _canPin = result;
+        return result;
+      }
    } on PlatformException catch (e) {
      debugPrint('canPin failed with code=${e.code}, exception=${e.message}, details=${e.details}}');
    }
    return false;
  }

-  static Future<void> pin(String label, AvesEntry entry, Set<CollectionFilter> filters) async {
-    Uint8List iconBytes;
+  static Future<void> pin(String label, AvesEntry? entry, Set<CollectionFilter> filters) async {
+    Uint8List? iconBytes;
    if (entry != null) {
      final size = entry.isVideo ? 0.0 : 256.0;
      iconBytes = await imageFileService.getThumbnail(
@ -44,7 +47,7 @@ class AppShortcutService {
      await platform.invokeMethod('pin', <String, dynamic>{
        'label': label,
        'iconBytes': iconBytes,
-        'filters': filters.where((filter) => filter != null).map((filter) => filter.toJson()).toList(),
+        'filters': filters.map((filter) => filter.toJson()).toList(),
      });
    } on PlatformException catch (e) {
      debugPrint('pin failed with code=${e.code}, exception=${e.message}, details=${e.details}');
--- a/lib/services/embedded_data_service.dart
+++ b/lib/services/embedded_data_service.dart
@ -11,7 +11,7 @@ abstract class EmbeddedDataService {

  Future<Map> extractVideoEmbeddedPicture(AvesEntry entry);

-  Future<Map> extractXmpDataProp(AvesEntry entry, String propPath, String propMimeType);
+  Future<Map> extractXmpDataProp(AvesEntry entry, String? propPath, String? propMimeType);
 }

 class PlatformEmbeddedDataService implements EmbeddedDataService {
@ -25,7 +25,7 @@ class PlatformEmbeddedDataService implements EmbeddedDataService {
        'uri': entry.uri,
        'sizeBytes': entry.sizeBytes,
      });
-      return (result as List).cast<Uint8List>();
+      if (result != null) return (result as List).cast<Uint8List>();
    } on PlatformException catch (e) {
      debugPrint('getExifThumbnail failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -41,11 +41,11 @@ class PlatformEmbeddedDataService implements EmbeddedDataService {
        'sizeBytes': entry.sizeBytes,
        'displayName': '${entry.bestTitle} • Video',
      });
-      return result;
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('extractMotionPhotoVideo failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
-    return null;
+    return {};
  }

  @override
@ -55,15 +55,15 @@ class PlatformEmbeddedDataService implements EmbeddedDataService {
        'uri': entry.uri,
        'displayName': '${entry.bestTitle} • Cover',
      });
-      return result;
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('extractVideoEmbeddedPicture failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
-    return null;
+    return {};
  }

  @override
-  Future<Map> extractXmpDataProp(AvesEntry entry, String propPath, String propMimeType) async {
+  Future<Map> extractXmpDataProp(AvesEntry entry, String? propPath, String? propMimeType) async {
    try {
      final result = await platform.invokeMethod('extractXmpDataProp', <String, dynamic>{
        'mimeType': entry.mimeType,
@ -73,10 +73,10 @@ class PlatformEmbeddedDataService implements EmbeddedDataService {
        'propPath': propPath,
        'propMimeType': propMimeType,
      });
-      return result;
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('extractXmpDataProp failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
-    return null;
+    return {};
  }
 }
--- a/lib/services/geocoding_service.dart
+++ b/lib/services/geocoding_service.dart
@ -29,7 +29,7 @@ class GeocodingService {

@immutable
 class Address {
-  final String addressLine, adminArea, countryCode, countryName, featureName, locality, postalCode, subAdminArea, subLocality, subThoroughfare, thoroughfare;
+  final String? addressLine, adminArea, countryCode, countryName, featureName, locality, postalCode, subAdminArea, subLocality, subThoroughfare, thoroughfare;

  const Address({
    this.addressLine,
--- a/lib/services/image_file_service.dart
+++ b/lib/services/image_file_service.dart
@ -7,28 +7,30 @@ import 'package:aves/model/entry.dart';
 import 'package:aves/ref/mime_types.dart';
 import 'package:aves/services/image_op_events.dart';
 import 'package:aves/services/service_policy.dart';
+import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
+// ignore: import_of_legacy_library_into_null_safe
 import 'package:streams_channel/streams_channel.dart';

 abstract class ImageFileService {
-  Future<AvesEntry> getEntry(String uri, String mimeType);
+  Future<AvesEntry?> getEntry(String uri, String? mimeType);

  Future<Uint8List> getSvg(
    String uri,
    String mimeType, {
-    int expectedContentLength,
-    BytesReceivedCallback onBytesReceived,
+    int? expectedContentLength,
+    BytesReceivedCallback? onBytesReceived,
  });

  Future<Uint8List> getImage(
    String uri,
    String mimeType,
-    int rotationDegrees,
+    int? rotationDegrees,
    bool isFlipped, {
-    int pageId,
-    int expectedContentLength,
-    BytesReceivedCallback onBytesReceived,
+    int? pageId,
+    int? expectedContentLength,
+    BytesReceivedCallback? onBytesReceived,
  });

  // `rect`: region to decode, with coordinates in reference to `imageSize`
@ -40,21 +42,21 @@ abstract class ImageFileService {
    int sampleSize,
    Rectangle<int> regionRect,
    Size imageSize, {
-    int pageId,
-    Object taskKey,
-    int priority,
+    int? pageId,
+    Object? taskKey,
+    int? priority,
  });

  Future<Uint8List> getThumbnail({
-    @required String uri,
-    @required String mimeType,
-    @required int rotationDegrees,
-    @required int pageId,
-    @required bool isFlipped,
-    @required int dateModifiedSecs,
-    @required double extent,
-    Object taskKey,
-    int priority,
+    required String uri,
+    required String mimeType,
+    required int rotationDegrees,
+    required int? pageId,
+    required bool isFlipped,
+    required int? dateModifiedSecs,
+    required double extent,
+    Object? taskKey,
+    int? priority,
  });

  Future<void> clearSizedThumbnailDiskCache();
@ -63,27 +65,27 @@ abstract class ImageFileService {

  bool cancelThumbnail(Object taskKey);

-  Future<T> resumeLoading<T>(Object taskKey);
+  Future<T>? resumeLoading<T>(Object taskKey);

  Stream<ImageOpEvent> delete(Iterable<AvesEntry> entries);

  Stream<MoveOpEvent> move(
    Iterable<AvesEntry> entries, {
-    @required bool copy,
-    @required String destinationAlbum,
+    required bool copy,
+    required String destinationAlbum,
  });

  Stream<ExportOpEvent> export(
    Iterable<AvesEntry> entries, {
-    @required String mimeType,
-    @required String destinationAlbum,
+    required String mimeType,
+    required String destinationAlbum,
  });

-  Future<Map> rename(AvesEntry entry, String newName);
+  Future<Map<String, dynamic>> rename(AvesEntry entry, String newName);

-  Future<Map> rotate(AvesEntry entry, {@required bool clockwise});
+  Future<Map<String, dynamic>> rotate(AvesEntry entry, {required bool clockwise});

-  Future<Map> flip(AvesEntry entry);
+  Future<Map<String, dynamic>> flip(AvesEntry entry);
 }

 class PlatformImageFileService implements ImageFileService {
@ -108,7 +110,7 @@ class PlatformImageFileService implements ImageFileService {
  }

  @override
-  Future<AvesEntry> getEntry(String uri, String mimeType) async {
+  Future<AvesEntry?> getEntry(String uri, String? mimeType) async {
    try {
      final result = await platform.invokeMethod('getEntry', <String, dynamic>{
        'uri': uri,
@ -125,8 +127,8 @@ class PlatformImageFileService implements ImageFileService {
  Future<Uint8List> getSvg(
    String uri,
    String mimeType, {
-    int expectedContentLength,
-    BytesReceivedCallback onBytesReceived,
+    int? expectedContentLength,
+    BytesReceivedCallback? onBytesReceived,
  }) =>
      getImage(
        uri,
@ -141,11 +143,11 @@ class PlatformImageFileService implements ImageFileService {
  Future<Uint8List> getImage(
    String uri,
    String mimeType,
-    int rotationDegrees,
+    int? rotationDegrees,
    bool isFlipped, {
-    int pageId,
-    int expectedContentLength,
-    BytesReceivedCallback onBytesReceived,
+    int? pageId,
+    int? expectedContentLength,
+    BytesReceivedCallback? onBytesReceived,
  }) {
    try {
      final completer = Completer<Uint8List>.sync();
@ -155,7 +157,7 @@ class PlatformImageFileService implements ImageFileService {
        'uri': uri,
        'mimeType': mimeType,
        'rotationDegrees': rotationDegrees ?? 0,
-        'isFlipped': isFlipped ?? false,
+        'isFlipped': isFlipped,
        'pageId': pageId,
      }).listen(
        (data) {
@ -182,7 +184,7 @@ class PlatformImageFileService implements ImageFileService {
    } on PlatformException catch (e) {
      debugPrint('getImage failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
-    return Future.sync(() => null);
+    return Future.sync(() => Uint8List(0));
  }

  @override
@ -194,9 +196,9 @@ class PlatformImageFileService implements ImageFileService {
    int sampleSize,
    Rectangle<int> regionRect,
    Size imageSize, {
-    int pageId,
-    Object taskKey,
-    int priority,
+    int? pageId,
+    Object? taskKey,
+    int? priority,
  }) {
    return servicePolicy.call(
      () async {
@ -213,11 +215,11 @@ class PlatformImageFileService implements ImageFileService {
            'imageWidth': imageSize.width.toInt(),
            'imageHeight': imageSize.height.toInt(),
          });
-          return result as Uint8List;
+          if (result != null) return result as Uint8List;
        } on PlatformException catch (e) {
          debugPrint('getRegion failed with code=${e.code}, exception=${e.message}, details=${e.details}');
        }
-        return null;
+        return Uint8List(0);
      },
      priority: priority ?? ServiceCallPriority.getRegion,
      key: taskKey,
@ -226,18 +228,18 @@ class PlatformImageFileService implements ImageFileService {

  @override
  Future<Uint8List> getThumbnail({
-    @required String uri,
-    @required String mimeType,
-    @required int rotationDegrees,
-    @required int pageId,
-    @required bool isFlipped,
-    @required int dateModifiedSecs,
-    @required double extent,
-    Object taskKey,
-    int priority,
+    required String uri,
+    required String mimeType,
+    required int rotationDegrees,
+    required int? pageId,
+    required bool isFlipped,
+    required int? dateModifiedSecs,
+    required double extent,
+    Object? taskKey,
+    int? priority,
  }) {
    if (mimeType == MimeTypes.svg) {
-      return Future.sync(() => null);
+      return Future.sync(() => Uint8List(0));
    }
    return servicePolicy.call(
      () async {
@ -253,11 +255,11 @@ class PlatformImageFileService implements ImageFileService {
            'pageId': pageId,
            'defaultSizeDip': thumbnailDefaultSize,
          });
-          return result as Uint8List;
+          if (result != null) return result as Uint8List;
        } on PlatformException catch (e) {
          debugPrint('getThumbnail failed with code=${e.code}, exception=${e.message}, details=${e.details}');
        }
-        return null;
+        return Uint8List(0);
      },
      priority: priority ?? (extent == 0 ? ServiceCallPriority.getFastThumbnail : ServiceCallPriority.getSizedThumbnail),
      key: taskKey,
@ -280,7 +282,7 @@ class PlatformImageFileService implements ImageFileService {
  bool cancelThumbnail(Object taskKey) => servicePolicy.pause(taskKey, [ServiceCallPriority.getFastThumbnail, ServiceCallPriority.getSizedThumbnail]);

  @override
-  Future<T> resumeLoading<T>(Object taskKey) => servicePolicy.resume<T>(taskKey);
+  Future<T>? resumeLoading<T>(Object taskKey) => servicePolicy.resume<T>(taskKey);

  @override
  Stream<ImageOpEvent> delete(Iterable<AvesEntry> entries) {
@ -298,8 +300,8 @@ class PlatformImageFileService implements ImageFileService {
  @override
  Stream<MoveOpEvent> move(
    Iterable<AvesEntry> entries, {
-    @required bool copy,
-    @required String destinationAlbum,
+    required bool copy,
+    required String destinationAlbum,
  }) {
    try {
      return _opStreamChannel.receiveBroadcastStream(<String, dynamic>{
@ -317,8 +319,8 @@ class PlatformImageFileService implements ImageFileService {
  @override
  Stream<ExportOpEvent> export(
    Iterable<AvesEntry> entries, {
-    @required String mimeType,
-    @required String destinationAlbum,
+    required String mimeType,
+    required String destinationAlbum,
  }) {
    try {
      return _opStreamChannel.receiveBroadcastStream(<String, dynamic>{
@ -334,14 +336,14 @@ class PlatformImageFileService implements ImageFileService {
  }

  @override
-  Future<Map> rename(AvesEntry entry, String newName) async {
+  Future<Map<String, dynamic>> rename(AvesEntry entry, String newName) async {
    try {
      // returns map with: 'contentId' 'path' 'title' 'uri' (all optional)
      final result = await platform.invokeMethod('rename', <String, dynamic>{
        'entry': _toPlatformEntryMap(entry),
        'newName': newName,
-      }) as Map;
-      return result;
+      });
+      if (result != null) return (result as Map).cast<String, dynamic>();
    } on PlatformException catch (e) {
      debugPrint('rename failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -349,14 +351,14 @@ class PlatformImageFileService implements ImageFileService {
  }

  @override
-  Future<Map> rotate(AvesEntry entry, {@required bool clockwise}) async {
+  Future<Map<String, dynamic>> rotate(AvesEntry entry, {required bool clockwise}) async {
    try {
      // returns map with: 'rotationDegrees' 'isFlipped'
      final result = await platform.invokeMethod('rotate', <String, dynamic>{
        'entry': _toPlatformEntryMap(entry),
        'clockwise': clockwise,
-      }) as Map;
-      return result;
+      });
+      if (result != null) return (result as Map).cast<String, dynamic>();
    } on PlatformException catch (e) {
      debugPrint('rotate failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -364,13 +366,13 @@ class PlatformImageFileService implements ImageFileService {
  }

  @override
-  Future<Map> flip(AvesEntry entry) async {
+  Future<Map<String, dynamic>> flip(AvesEntry entry) async {
    try {
      // returns map with: 'rotationDegrees' 'isFlipped'
      final result = await platform.invokeMethod('flip', <String, dynamic>{
        'entry': _toPlatformEntryMap(entry),
-      }) as Map;
-      return result;
+      });
+      if (result != null) return (result as Map).cast<String, dynamic>();
    } on PlatformException catch (e) {
      debugPrint('flip failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -379,18 +381,18 @@ class PlatformImageFileService implements ImageFileService {
 }

 // cf flutter/foundation `consolidateHttpClientResponseBytes`
-typedef BytesReceivedCallback = void Function(int cumulative, int total);
+typedef BytesReceivedCallback = void Function(int cumulative, int? total);

 // cf flutter/foundation `consolidateHttpClientResponseBytes`
 class _OutputBuffer extends ByteConversionSinkBase {
-  List<List<int>> _chunks = <List<int>>[];
+  List<List<int>>? _chunks = <List<int>>[];
  int _contentLength = 0;
-  Uint8List _bytes;
+  Uint8List? _bytes;

  @override
  void add(List<int> chunk) {
    assert(_bytes == null);
-    _chunks.add(chunk);
+    _chunks!.add(chunk);
    _contentLength += chunk.length;
  }

@ -402,8 +404,8 @@ class _OutputBuffer extends ByteConversionSinkBase {
    }
    _bytes = Uint8List(_contentLength);
    var offset = 0;
-    for (final chunk in _chunks) {
-      _bytes.setRange(offset, offset + chunk.length, chunk);
+    for (final chunk in _chunks!) {
+      _bytes!.setRange(offset, offset + chunk.length, chunk);
      offset += chunk.length;
    }
    _chunks = null;
@ -411,6 +413,6 @@ class _OutputBuffer extends ByteConversionSinkBase {

  Uint8List get bytes {
    assert(_bytes != null);
-    return _bytes;
+    return _bytes!;
  }
 }
--- a/lib/services/image_op_events.dart
+++ b/lib/services/image_op_events.dart
@ -7,8 +7,8 @@ class ImageOpEvent {
  final String uri;

  const ImageOpEvent({
-    this.success,
-    this.uri,
+    required this.success,
+    required this.uri,
  });

  factory ImageOpEvent.fromMap(Map map) {
@ -34,7 +34,7 @@ class ImageOpEvent {
 class MoveOpEvent extends ImageOpEvent {
  final Map newFields;

-  const MoveOpEvent({bool success, String uri, this.newFields})
+  const MoveOpEvent({required bool success, required String uri, required this.newFields})
      : super(
          success: success,
          uri: uri,
@ -44,7 +44,7 @@ class MoveOpEvent extends ImageOpEvent {
    return MoveOpEvent(
      success: map['success'] ?? false,
      uri: map['uri'],
-      newFields: map['newFields'],
+      newFields: map['newFields'] ?? {},
    );
  }

@ -53,9 +53,9 @@ class MoveOpEvent extends ImageOpEvent {
 }

 class ExportOpEvent extends MoveOpEvent {
-  final int pageId;
+  final int? pageId;

-  const ExportOpEvent({bool success, String uri, this.pageId, Map newFields})
+  const ExportOpEvent({required bool success, required String uri, this.pageId, required Map newFields})
      : super(
          success: success,
          uri: uri,
@ -67,7 +67,7 @@ class ExportOpEvent extends MoveOpEvent {
      success: map['success'] ?? false,
      uri: map['uri'],
      pageId: map['pageId'],
-      newFields: map['newFields'],
+      newFields: map['newFields'] ?? {},
    );
  }

--- a/lib/services/media_store_service.dart
+++ b/lib/services/media_store_service.dart
@ -3,12 +3,13 @@ import 'dart:async';
 import 'package:aves/model/entry.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
+// ignore: import_of_legacy_library_into_null_safe
 import 'package:streams_channel/streams_channel.dart';

 abstract class MediaStoreService {
  Future<List<int>> checkObsoleteContentIds(List<int> knownContentIds);

-  Future<List<int>> checkObsoletePaths(Map<int, String> knownPathById);
+  Future<List<int>> checkObsoletePaths(Map<int, String?> knownPathById);

  // knownEntries: map of contentId -> dateModifiedSecs
  Stream<AvesEntry> getEntries(Map<int, int> knownEntries);
@ -32,7 +33,7 @@ class PlatformMediaStoreService implements MediaStoreService {
  }

  @override
-  Future<List<int>> checkObsoletePaths(Map<int, String> knownPathById) async {
+  Future<List<int>> checkObsoletePaths(Map<int, String?> knownPathById) async {
    try {
      final result = await platform.invokeMethod('checkObsoletePaths', <String, dynamic>{
        'knownPathById': knownPathById,
--- a/lib/services/metadata_service.dart
+++ b/lib/services/metadata_service.dart
@ -10,15 +10,15 @@ abstract class MetadataService {
  // returns Map<Map<Key, Value>> (map of directories, each directory being a map of metadata label and value description)
  Future<Map> getAllMetadata(AvesEntry entry);

-  Future<CatalogMetadata> getCatalogMetadata(AvesEntry entry, {bool background = false});
+  Future<CatalogMetadata?> getCatalogMetadata(AvesEntry entry, {bool background = false});

-  Future<OverlayMetadata> getOverlayMetadata(AvesEntry entry);
+  Future<OverlayMetadata?> getOverlayMetadata(AvesEntry entry);

-  Future<MultiPageInfo> getMultiPageInfo(AvesEntry entry);
+  Future<MultiPageInfo?> getMultiPageInfo(AvesEntry entry);

-  Future<PanoramaInfo> getPanoramaInfo(AvesEntry entry);
+  Future<PanoramaInfo?> getPanoramaInfo(AvesEntry entry);

-  Future<String> getContentResolverProp(AvesEntry entry, String prop);
+  Future<String?> getContentResolverProp(AvesEntry entry, String prop);
 }

 class PlatformMetadataService implements MetadataService {
@ -26,7 +26,7 @@ class PlatformMetadataService implements MetadataService {

  @override
  Future<Map> getAllMetadata(AvesEntry entry) async {
-    if (entry.isSvg) return null;
+    if (entry.isSvg) return {};

    try {
      final result = await platform.invokeMethod('getAllMetadata', <String, dynamic>{
@ -34,7 +34,7 @@ class PlatformMetadataService implements MetadataService {
        'uri': entry.uri,
        'sizeBytes': entry.sizeBytes,
      });
-      return result as Map;
+      if (result != null) return result as Map;
    } on PlatformException catch (e) {
      debugPrint('getAllMetadata failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
@ -42,10 +42,10 @@ class PlatformMetadataService implements MetadataService {
  }

  @override
-  Future<CatalogMetadata> getCatalogMetadata(AvesEntry entry, {bool background = false}) async {
+  Future<CatalogMetadata?> getCatalogMetadata(AvesEntry entry, {bool background = false}) async {
    if (entry.isSvg) return null;

-    Future<CatalogMetadata> call() async {
+    Future<CatalogMetadata?> call() async {
      try {
        // returns map with:
        // 'mimeType': MIME type as reported by metadata extractors, not Media Store (string)
@ -80,7 +80,7 @@ class PlatformMetadataService implements MetadataService {
  }

  @override
-  Future<OverlayMetadata> getOverlayMetadata(AvesEntry entry) async {
+  Future<OverlayMetadata?> getOverlayMetadata(AvesEntry entry) async {
    if (entry.isSvg) return null;

    try {
@ -98,7 +98,7 @@ class PlatformMetadataService implements MetadataService {
  }

  @override
-  Future<MultiPageInfo> getMultiPageInfo(AvesEntry entry) async {
+  Future<MultiPageInfo?> getMultiPageInfo(AvesEntry entry) async {
    try {
      final result = await platform.invokeMethod('getMultiPageInfo', <String, dynamic>{
        'mimeType': entry.mimeType,
@ -120,7 +120,7 @@ class PlatformMetadataService implements MetadataService {
  }

  @override
-  Future<PanoramaInfo> getPanoramaInfo(AvesEntry entry) async {
+  Future<PanoramaInfo?> getPanoramaInfo(AvesEntry entry) async {
    try {
      // returns map with values for:
      // 'croppedAreaLeft' (int), 'croppedAreaTop' (int), 'croppedAreaWidth' (int), 'croppedAreaHeight' (int),
@ -138,7 +138,7 @@ class PlatformMetadataService implements MetadataService {
  }

  @override
-  Future<String> getContentResolverProp(AvesEntry entry, String prop) async {
+  Future<String?> getContentResolverProp(AvesEntry entry, String prop) async {
    try {
      return await platform.invokeMethod('getContentResolverProp', <String, dynamic>{
        'mimeType': entry.mimeType,
--- a/lib/services/service_policy.dart
+++ b/lib/services/service_policy.dart
@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:collection';

+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:tuple/tuple.dart';

@ -22,19 +23,19 @@ class ServicePolicy {
  Future<T> call<T>(
    Future<T> Function() platformCall, {
    int priority = ServiceCallPriority.normal,
-    Object key,
+    Object? key,
  }) {
    Completer<T> completer;
-    _Task task;
+    _Task<T > task;
    key ??= platformCall.hashCode;
    final toResume = _paused.remove(key);
    if (toResume != null) {
      priority = toResume.item1;
-      task = toResume.item2;
+      task = toResume.item2 as _Task<T>;
      completer = task.completer;
    } else {
      completer = Completer<T>();
-      task = _Task(
+      task = _Task<T>(
        () async {
          try {
            completer.complete(await platformCall());
@ -52,11 +53,11 @@ class ServicePolicy {
    return completer.future;
  }

-  Future<T> resume<T>(Object key) {
+  Future<T>? resume<T>(Object key) {
    final toResume = _paused.remove(key);
    if (toResume != null) {
      final priority = toResume.item1;
-      final task = toResume.item2;
+      final task = toResume.item2 as _Task<T >;
      _getQueue(priority)[key] = task;
      _pickNext();
      return task.completer.future;
@ -70,10 +71,10 @@ class ServicePolicy {
  void _pickNext() {
    _notifyQueueState();
    if (_runningQueue.length >= concurrentTaskMax) return;
-    final queue = _queues.entries.firstWhere((kv) => kv.value.isNotEmpty, orElse: () => null)?.value;
+    final queue = _queues.entries.firstWhereOrNull((kv) => kv.value.isNotEmpty)?.value;
    if (queue != null && queue.isNotEmpty) {
      final key = queue.keys.first;
-      final task = queue.remove(key);
+      final task = queue.remove(key)!;
      _runningQueue[key] = task;
      task.callback();
    }
@ -109,9 +110,9 @@ class ServicePolicy {
  }
 }

-class _Task {
+class _Task<T> {
  final VoidCallback callback;
-  final Completer completer;
+  final Completer<T> completer;

  const _Task(this.callback, this.completer);
 }
--- a/lib/services/services.dart
+++ b/lib/services/services.dart
@ -11,16 +11,16 @@ import 'package:path/path.dart' as p;

 final getIt = GetIt.instance;

-final pContext = getIt<p.Context>();
-final availability = getIt<AvesAvailability>();
-final metadataDb = getIt<MetadataDb>();
+final p.Context pContext = getIt<p.Context>();
+final AvesAvailability availability = getIt<AvesAvailability>();
+final MetadataDb metadataDb = getIt<MetadataDb>();

-final embeddedDataService = getIt<EmbeddedDataService>();
-final imageFileService = getIt<ImageFileService>();
-final mediaStoreService = getIt<MediaStoreService>();
-final metadataService = getIt<MetadataService>();
-final storageService = getIt<StorageService>();
-final timeService = getIt<TimeService>();
+final EmbeddedDataService embeddedDataService = getIt<EmbeddedDataService>();
+final ImageFileService imageFileService = getIt<ImageFileService>();
+final MediaStoreService mediaStoreService = getIt<MediaStoreService>();
+final MetadataService metadataService = getIt<MetadataService>();
+final StorageService storageService = getIt<StorageService>();
+final TimeService timeService = getIt<TimeService>();

 void initPlatformServices() {
  getIt.registerLazySingleton<p.Context>(() => p.Context());
--- a/lib/services/storage_service.dart
+++ b/lib/services/storage_service.dart
@ -3,12 +3,13 @@ import 'dart:async';
 import 'package:aves/utils/android_file_utils.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
+// ignore: import_of_legacy_library_into_null_safe
 import 'package:streams_channel/streams_channel.dart';

 abstract class StorageService {
  Future<Set<StorageVolume>> getStorageVolumes();

-  Future<int> getFreeSpace(StorageVolume volume);
+  Future<int?> getFreeSpace(StorageVolume volume);

  Future<List<String>> getGrantedDirectories();

@ -25,7 +26,7 @@ abstract class StorageService {
  Future<int> deleteEmptyDirectories(Iterable<String> dirPaths);

  // returns media URI
-  Future<Uri> scanFile(String path, String mimeType);
+  Future<Uri?> scanFile(String path, String mimeType);
 }

 class PlatformStorageService implements StorageService {
@ -44,16 +45,16 @@ class PlatformStorageService implements StorageService {
  }

  @override
-  Future<int> getFreeSpace(StorageVolume volume) async {
+  Future<int?> getFreeSpace(StorageVolume volume) async {
    try {
      final result = await platform.invokeMethod('getFreeSpace', <String, dynamic>{
        'path': volume.path,
      });
-      return result as int;
+      return result as int?;
    } on PlatformException catch (e) {
      debugPrint('getFreeSpace failed with code=${e.code}, exception=${e.message}, details=${e.details}}');
    }
-    return 0;
+    return null;
  }

  @override
@ -85,22 +86,26 @@ class PlatformStorageService implements StorageService {
      final result = await platform.invokeMethod('getInaccessibleDirectories', <String, dynamic>{
        'dirPaths': dirPaths.toList(),
      });
-      return (result as List).cast<Map>().map((map) => VolumeRelativeDirectory.fromMap(map)).toSet();
+      if (result != null) {
+        return (result as List).cast<Map>().map(VolumeRelativeDirectory.fromMap).toSet();
+      }
    } on PlatformException catch (e) {
      debugPrint('getInaccessibleDirectories failed with code=${e.code}, exception=${e.message}, details=${e.details}}');
    }
-    return null;
+    return {};
  }

  @override
  Future<Set<VolumeRelativeDirectory>> getRestrictedDirectories() async {
    try {
      final result = await platform.invokeMethod('getRestrictedDirectories');
-      return (result as List).cast<Map>().map((map) => VolumeRelativeDirectory.fromMap(map)).toSet();
+      if (result != null) {
+        return (result as List).cast<Map>().map(VolumeRelativeDirectory.fromMap).toSet();
+      }
    } on PlatformException catch (e) {
      debugPrint('getRestrictedDirectories failed with code=${e.code}, exception=${e.message}, details=${e.details}}');
    }
-    return null;
+    return {};
  }

  // returns whether user granted access to volume root at `volumePath`
@ -111,7 +116,7 @@ class PlatformStorageService implements StorageService {
      storageAccessChannel.receiveBroadcastStream(<String, dynamic>{
        'path': volumePath,
      }).listen(
-        (data) => completer.complete(data as bool),
+        (data) => completer.complete(data as bool?),
        onError: completer.completeError,
        onDone: () {
          if (!completer.isCompleted) completer.complete(false);
@ -129,9 +134,10 @@ class PlatformStorageService implements StorageService {
  @override
  Future<int> deleteEmptyDirectories(Iterable<String> dirPaths) async {
    try {
-      return await platform.invokeMethod('deleteEmptyDirectories', <String, dynamic>{
+      final result = await platform.invokeMethod('deleteEmptyDirectories', <String, dynamic>{
        'dirPaths': dirPaths.toList(),
      });
+      if (result != null) return result as int;
    } on PlatformException catch (e) {
      debugPrint('deleteEmptyDirectories failed with code=${e.code}, exception=${e.message}, details=${e.details}}');
    }
@ -140,14 +146,14 @@ class PlatformStorageService implements StorageService {

  // returns media URI
  @override
-  Future<Uri> scanFile(String path, String mimeType) async {
+  Future<Uri?> scanFile(String path, String mimeType) async {
    debugPrint('scanFile with path=$path, mimeType=$mimeType');
    try {
-      final uriString = await platform.invokeMethod('scanFile', <String, dynamic>{
+      final result = await platform.invokeMethod('scanFile', <String, dynamic>{
        'path': path,
        'mimeType': mimeType,
      });
-      return Uri.tryParse(uriString ?? '');
+      if (result != null) return Uri.tryParse(result);
    } on PlatformException catch (e) {
      debugPrint('scanFile failed with code=${e.code}, exception=${e.message}, details=${e.details}}');
    }
--- a/lib/services/svg_metadata_service.dart
+++ b/lib/services/svg_metadata_service.dart
@ -3,6 +3,7 @@ import 'dart:convert';
 import 'package:aves/model/entry.dart';
 import 'package:aves/services/services.dart';
 import 'package:aves/utils/string_utils.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:xml/xml.dart';
@ -15,15 +16,15 @@ class SvgMetadataService {
  static const _textElements = ['title', 'desc'];
  static const _metadataElement = 'metadata';

-  static Future<Size> getSize(AvesEntry entry) async {
+  static Future<Size?> getSize(AvesEntry entry) async {
    try {
      final data = await imageFileService.getSvg(entry.uri, entry.mimeType);

      final document = XmlDocument.parse(utf8.decode(data));
      final root = document.rootElement;

-      String getAttribute(String attributeName) => root.attributes.firstWhere((a) => a.name.qualified == attributeName, orElse: () => null)?.value;
-      double tryParseWithoutUnit(String s) => s == null ? null : double.tryParse(s.replaceAll(RegExp(r'[a-z%]'), ''));
+      String? getAttribute(String attributeName) => root.attributes.firstWhereOrNull((a) => a.name.qualified == attributeName)?.value;
+      double? tryParseWithoutUnit(String? s) => s == null ? null : double.tryParse(s.replaceAll(RegExp(r'[a-z%]'), ''));

      final width = tryParseWithoutUnit(getAttribute('width'));
      final height = tryParseWithoutUnit(getAttribute('height'));
@ -37,7 +38,7 @@ class SvgMetadataService {
        if (parts.length == 4) {
          final vbWidth = tryParseWithoutUnit(parts[2]);
          final vbHeight = tryParseWithoutUnit(parts[3]);
-          if (vbWidth > 0 && vbHeight > 0) {
+          if (vbWidth != null && vbWidth > 0 && vbHeight != null && vbHeight > 0) {
            return Size(vbWidth, vbHeight);
          }
        }
@ -66,7 +67,7 @@ class SvgMetadataService {

      final docDir = Map.fromEntries([
        ...root.attributes.where((a) => _attributes.contains(a.name.qualified)).map((a) => MapEntry(formatKey(a.name.qualified), a.value)),
-        ..._textElements.map((name) => MapEntry(formatKey(name), root.getElement(name)?.text)).where((kv) => kv.value != null),
+        ..._textElements.map((name) => MapEntry(formatKey(name), root.getElement(name)?.text)).where((kv) => kv.value != null).cast<MapEntry<String, String >>(),
      ]);

      final metadata = root.getElement(_metadataElement);
@ -80,7 +81,7 @@ class SvgMetadataService {
      };
    } catch (error, stack) {
      debugPrint('failed to parse XML from SVG with error=$error\n$stack');
-      return null;
    }
+    return {};
  }
 }
--- a/lib/services/time_service.dart
+++ b/lib/services/time_service.dart
@ -2,14 +2,14 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';

 abstract class TimeService {
-  Future<String> getDefaultTimeZone();
+  Future<String?> getDefaultTimeZone();
 }

 class PlatformTimeService implements TimeService {
  static const platform = MethodChannel('deckers.thibault/aves/time');

  @override
-  Future<String> getDefaultTimeZone() async {
+  Future<String?> getDefaultTimeZone() async {
    try {
      return await platform.invokeMethod('getDefaultTimeZone');
    } on PlatformException catch (e) {
--- a/lib/services/viewer_service.dart
+++ b/lib/services/viewer_service.dart
@ -4,10 +4,11 @@ import 'package:flutter/services.dart';
 class ViewerService {
  static const platform = MethodChannel('deckers.thibault/aves/viewer');

-  static Future<Map> getIntentData() async {
+  static Future<Map<String, dynamic>> getIntentData() async {
    try {
      // returns nullable map with 'action' and possibly 'uri' 'mimeType'
-      return await platform.invokeMethod('getIntentData') as Map;
+      final result = await platform.invokeMethod('getIntentData');
+      if (result != null) return (result as Map).cast<String, dynamic>();
    } on PlatformException catch (e) {
      debugPrint('getIntentData failed with code=${e.code}, exception=${e.message}, details=${e.details}');
    }
--- a/lib/theme/durations.dart
+++ b/lib/theme/durations.dart
@ -32,14 +32,13 @@ class Durations {
  static const collectionOpOverlayAnimation = Duration(milliseconds: 300);
  static const collectionScalingBackgroundAnimation = Duration(milliseconds: 200);
  static const sectionHeaderAnimation = Duration(milliseconds: 200);
-  static const thumbnailTransition = Duration(milliseconds: 200);
  static const thumbnailOverlayAnimation = Duration(milliseconds: 200);

  // search animations
  static const filterRowExpandAnimation = Duration(milliseconds: 300);

  // viewer animations
-  static const viewerVerticalPageScrollAnimation = Duration(milliseconds: 300);
+  static const viewerVerticalPageScrollAnimation = Duration(milliseconds: 500);
  static const viewerOverlayAnimation = Duration(milliseconds: 200);
  static const viewerOverlayChangeAnimation = Duration(milliseconds: 150);
  static const viewerOverlayPageScrollAnimation = Duration(milliseconds: 200);
@ -56,8 +55,10 @@ class Durations {

  // delays & refresh intervals
  static const opToastDisplay = Duration(seconds: 3);
+  static const opToastActionDisplay = Duration(seconds: 5);
+  static const infoScrollMonitoringTimerDelay = Duration(milliseconds: 100);
  static const collectionScrollMonitoringTimerDelay = Duration(milliseconds: 100);
-  static const collectionScalingCompleteNotificationDelay = Duration(milliseconds: 300);
+  static const highlightJumpDelay = Duration(milliseconds: 400);
  static const highlightScrollInitDelay = Duration(milliseconds: 800);
  static const videoProgressTimerInterval = Duration(milliseconds: 300);
  static Duration staggeredAnimationDelay = Durations.staggeredAnimation ~/ 6 * timeDilation;
--- a/lib/theme/icons.dart
+++ b/lib/theme/icons.dart
@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+// ignore: import_of_legacy_library_into_null_safe
 import 'package:material_design_icons_flutter/material_design_icons_flutter.dart';

 class AIcons {
@ -19,7 +20,7 @@ class AIcons {
  static const IconData location = Icons.place_outlined;
  static const IconData locationOff = Icons.location_off_outlined;
  static const IconData privacy = MdiIcons.shieldAccountOutline;
-  static const IconData raw = Icons.camera_outlined;
+  static const IconData raw = Icons.raw_on_outlined;
  static const IconData shooting = Icons.camera_outlined;
  static const IconData removableStorage = Icons.sd_storage_outlined;
  static const IconData sensorControl = Icons.explore_outlined;
--- a/lib/theme/themes.dart
+++ b/lib/theme/themes.dart
@ -9,13 +9,13 @@ class Themes {
  static final darkTheme = ThemeData(
    brightness: Brightness.dark,
    accentColor: _accentColor,
-    scaffoldBackgroundColor: Colors.grey[900],
+    scaffoldBackgroundColor: Colors.grey.shade900,
    dialogBackgroundColor: Colors.grey[850],
    toggleableActiveColor: _accentColor,
-    tooltipTheme: TooltipThemeData(
+    tooltipTheme: const TooltipThemeData(
      verticalOffset: 32,
    ),
-    appBarTheme: AppBarTheme(
+    appBarTheme: const AppBarTheme(
      textTheme: TextTheme(
        headline6: TextStyle(
          fontSize: 20,
@ -24,15 +24,16 @@ class Themes {
        ),
      ),
    ),
-    colorScheme: ColorScheme.dark(
+    colorScheme: const ColorScheme.dark(
      primary: _accentColor,
      secondary: _accentColor,
      onPrimary: Colors.white,
      onSecondary: Colors.white,
    ),
    snackBarTheme: SnackBarThemeData(
-      backgroundColor: Colors.grey[800],
-      contentTextStyle: TextStyle(
+      backgroundColor: Colors.grey.shade800,
+      actionTextColor: _accentColor,
+      contentTextStyle: const TextStyle(
        color: Colors.white,
      ),
      behavior: SnackBarBehavior.floating,
--- a/lib/utils/android_file_utils.dart
+++ b/lib/utils/android_file_utils.dart
@ -2,13 +2,14 @@ import 'package:aves/services/android_app_service.dart';
 import 'package:aves/services/services.dart';
 import 'package:aves/utils/change_notifier.dart';
 import 'package:aves/widgets/common/extensions/build_context.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

 final AndroidFileUtils androidFileUtils = AndroidFileUtils._private();

 class AndroidFileUtils {
-  String primaryStorage, dcimPath, downloadPath, moviesPath, picturesPath;
+  late String primaryStorage, dcimPath, downloadPath, moviesPath, picturesPath;
  Set<StorageVolume> storageVolumes = {};
  Set<Package> _packages = {};
  List<String> _potentialAppDirs = [];
@ -22,7 +23,7 @@ class AndroidFileUtils {
  Future<void> init() async {
    storageVolumes = await storageService.getStorageVolumes();
    // path_provider getExternalStorageDirectory() gives '/storage/emulated/0/Android/data/deckers.thibault.aves/files'
-    primaryStorage = storageVolumes.firstWhere((volume) => volume.isPrimary).path;
+    primaryStorage = storageVolumes.firstWhereOrNull((volume) => volume.isPrimary)?.path ?? '/';
    dcimPath = pContext.join(primaryStorage, 'DCIM');
    downloadPath = pContext.join(primaryStorage, 'Download');
    moviesPath = pContext.join(primaryStorage, 'Movies');
@ -35,16 +36,17 @@ class AndroidFileUtils {
    appNameChangeNotifier.notifyListeners();
  }

-  bool isCameraPath(String path) => path != null && path.startsWith(dcimPath) && (path.endsWith('Camera') || path.endsWith('100ANDRO'));
+  bool isCameraPath(String path) => path.startsWith(dcimPath) && (path.endsWith('Camera') || path.endsWith('100ANDRO'));

-  bool isScreenshotsPath(String path) => path != null && (path.startsWith(dcimPath) || path.startsWith(picturesPath)) && path.endsWith('Screenshots');
+  bool isScreenshotsPath(String path) => (path.startsWith(dcimPath) || path.startsWith(picturesPath)) && path.endsWith('Screenshots');

-  bool isScreenRecordingsPath(String path) => path != null && (path.startsWith(dcimPath) || path.startsWith(moviesPath)) && (path.endsWith('Screen recordings') || path.endsWith('ScreenRecords'));
+  bool isScreenRecordingsPath(String path) => (path.startsWith(dcimPath) || path.startsWith(moviesPath)) && (path.endsWith('Screen recordings') || path.endsWith('ScreenRecords'));

  bool isDownloadPath(String path) => path == downloadPath;

-  StorageVolume getStorageVolume(String path) {
-    final volume = storageVolumes.firstWhere((v) => path.startsWith(v.path), orElse: () => null);
+  StorageVolume? getStorageVolume(String? path) {
+    if (path == null) return null;
+    final volume = storageVolumes.firstWhereOrNull((v) => path.startsWith(v.path));
    // storage volume path includes trailing '/', but argument path may or may not,
    // which is an issue when the path is at the root
    return volume != null || path.endsWith('/') ? volume : getStorageVolume('$path/');
@ -53,27 +55,25 @@ class AndroidFileUtils {
  bool isOnRemovableStorage(String path) => getStorageVolume(path)?.isRemovable ?? false;

  AlbumType getAlbumType(String albumPath) {
-    if (albumPath != null) {
-      if (isCameraPath(albumPath)) return AlbumType.camera;
-      if (isDownloadPath(albumPath)) return AlbumType.download;
-      if (isScreenRecordingsPath(albumPath)) return AlbumType.screenRecordings;
-      if (isScreenshotsPath(albumPath)) return AlbumType.screenshots;
+    if (isCameraPath(albumPath)) return AlbumType.camera;
+    if (isDownloadPath(albumPath)) return AlbumType.download;
+    if (isScreenRecordingsPath(albumPath)) return AlbumType.screenRecordings;
+    if (isScreenshotsPath(albumPath)) return AlbumType.screenshots;
+
+    final dir = pContext.split(albumPath).last;
+    if (albumPath.startsWith(primaryStorage) && _potentialAppDirs.contains(dir)) return AlbumType.app;

-      final dir = pContext.split(albumPath).last;
-      if (albumPath.startsWith(primaryStorage) && _potentialAppDirs.contains(dir)) return AlbumType.app;
-    }
    return AlbumType.regular;
  }

-  String getAlbumAppPackageName(String albumPath) {
-    if (albumPath == null) return null;
+  String? getAlbumAppPackageName(String albumPath) {
    final dir = pContext.split(albumPath).last;
-    final package = _launcherPackages.firstWhere((package) => package.potentialDirs.contains(dir), orElse: () => null);
+    final package = _launcherPackages.firstWhereOrNull((package) => package.potentialDirs.contains(dir));
    return package?.packageName;
  }

-  String getCurrentAppName(String packageName) {
-    final package = _packages.firstWhere((package) => package.packageName == packageName, orElse: () => null);
+  String? getCurrentAppName(String packageName) {
+    final package = _packages.firstWhereOrNull((package) => package.packageName == packageName);
    return package?.currentLabel;
  }
 }
@ -81,25 +81,26 @@ class AndroidFileUtils {
 enum AlbumType { regular, app, camera, download, screenRecordings, screenshots }

 class Package {
-  final String packageName, currentLabel, englishLabel;
+  final String packageName;
+  final String? currentLabel, englishLabel;
  final bool categoryLauncher, isSystem;
  final Set<String> ownedDirs = {};

  Package({
-    this.packageName,
-    this.currentLabel,
-    this.englishLabel,
-    this.categoryLauncher,
-    this.isSystem,
+    required this.packageName,
+    required this.currentLabel,
+    required this.englishLabel,
+    required this.categoryLauncher,
+    required this.isSystem,
  });

  factory Package.fromMap(Map map) {
    return Package(
-      packageName: map['packageName'],
+      packageName: map['packageName'] ?? '',
      currentLabel: map['currentLabel'],
      englishLabel: map['englishLabel'],
-      categoryLauncher: map['categoryLauncher'],
-      isSystem: map['isSystem'],
+      categoryLauncher: map['categoryLauncher'] ?? false,
+      isSystem: map['isSystem'] ?? false,
    );
  }

@ -107,7 +108,7 @@ class Package {
        currentLabel,
        englishLabel,
        ...ownedDirs,
-      ].where((dir) => dir != null).toSet();
+      ].where((dir) => dir != null).cast<String>().toSet();

  @override
  String toString() => '$runtimeType#${shortHash(this)}{packageName=$packageName, categoryLauncher=$categoryLauncher, isSystem=$isSystem, currentLabel=$currentLabel, englishLabel=$englishLabel, ownedDirs=$ownedDirs}';
@ -115,24 +116,25 @@ class Package {

@immutable
 class StorageVolume {
-  final String _description, path, state;
+  final String? _description;
+  final String path, state;
  final bool isPrimary, isRemovable;

  const StorageVolume({
-    String description,
-    this.isPrimary,
-    this.isRemovable,
-    this.path,
-    this.state,
+    required String? description,
+    required this.isPrimary,
+    required this.isRemovable,
+    required this.path,
+    required this.state,
  }) : _description = description;

-  String getDescription(BuildContext context) {
-    if (_description != null) return _description;
+  String getDescription(BuildContext? context) {
+    if (_description != null) return _description!;
    // ideally, the context should always be provided, but in some cases (e.g. album comparison),
    // this would require numerous additional methods to have the context as argument
    // for such a minor benefit: fallback volume description on Android < N
-    if (isPrimary) return context?.l10n?.storageVolumeDescriptionFallbackPrimary ?? 'Internal Storage';
-    return context?.l10n?.storageVolumeDescriptionFallbackNonPrimary ?? 'SD card';
+    if (isPrimary) return context?.l10n.storageVolumeDescriptionFallbackPrimary ?? 'Internal Storage';
+    return context?.l10n.storageVolumeDescriptionFallbackNonPrimary ?? 'SD card';
  }

  factory StorageVolume.fromMap(Map map) {
@ -152,19 +154,19 @@ class VolumeRelativeDirectory {
  final String volumePath, relativeDir;

  const VolumeRelativeDirectory({
-    this.volumePath,
-    this.relativeDir,
+    required this.volumePath,
+    required this.relativeDir,
  });

-  factory VolumeRelativeDirectory.fromMap(Map map) {
+  static VolumeRelativeDirectory fromMap(Map map) {
    return VolumeRelativeDirectory(
-      volumePath: map['volumePath'],
+      volumePath: map['volumePath'] ?? '',
      relativeDir: map['relativeDir'] ?? '',
    );
  }

  // prefer static method over a null returning factory constructor
-  static VolumeRelativeDirectory fromPath(String dirPath) {
+  static VolumeRelativeDirectory? fromPath(String dirPath) {
    final volume = androidFileUtils.getStorageVolume(dirPath);
    if (volume == null) return null;

@ -177,7 +179,7 @@ class VolumeRelativeDirectory {
  }

  String getVolumeDescription(BuildContext context) {
-    final volume = androidFileUtils.storageVolumes.firstWhere((volume) => volume.path == volumePath, orElse: () => null);
+    final volume = androidFileUtils.storageVolumes.firstWhereOrNull((volume) => volume.path == volumePath);
    return volume?.getDescription(context) ?? volumePath;
  }

--- a/lib/utils/change_notifier.dart
+++ b/lib/utils/change_notifier.dart
@ -2,22 +2,22 @@ import 'package:flutter/foundation.dart';

 // reimplemented ChangeNotifier so that it can be used anywhere, not just as a mixin
 class AChangeNotifier implements Listenable {
-  ObserverList<VoidCallback> _listeners = ObserverList<VoidCallback>();
+  ObserverList<VoidCallback>? _listeners = ObserverList<VoidCallback>();

  @override
-  void addListener(VoidCallback listener) => _listeners.add(listener);
+  void addListener(VoidCallback listener) => _listeners!.add(listener);

  @override
-  void removeListener(VoidCallback listener) => _listeners.remove(listener);
+  void removeListener(VoidCallback listener) => _listeners!.remove(listener);

  void dispose() => _listeners = null;

  void notifyListeners() {
    if (_listeners == null) return;
-    final localListeners = List<VoidCallback>.from(_listeners);
+    final localListeners = List<VoidCallback>.from(_listeners!);
    for (final listener in localListeners) {
      try {
-        if (_listeners.contains(listener)) listener();
+        if (_listeners!.contains(listener)) listener();
      } catch (error, stack) {
        debugPrint('$runtimeType failed to notify listeners with error=$error\n$stack');
      }
--- a/lib/utils/constants.dart
+++ b/lib/utils/constants.dart
@ -15,10 +15,12 @@ class Constants {
    fontFeatures: [FontFeature.enable('smcp')],
  );

-  static const embossShadow = Shadow(
-    color: Colors.black87,
-    offset: Offset(0.5, 1.0),
-  );
+  static const embossShadows = [
+    Shadow(
+      color: Colors.black,
+      offset: Offset(0.5, 1.0),
+    )
+  ];

  static const overlayUnknown = '—'; // em dash

@ -40,7 +42,7 @@ class Constants {
      sourceUrl: 'https://android.googlesource.com/platform/frameworks/support/+/androidx-main/exifinterface/exifinterface',
    ),
    Dependency(
-      name: 'Android-TiffBitmapFactory',
+      name: 'Android-TiffBitmapFactory (Aves fork)',
      license: 'MIT',
      licenseUrl: 'https://github.com/deckerst/Android-TiffBitmapFactory/blob/master/license.txt',
      sourceUrl: 'https://github.com/deckerst/Android-TiffBitmapFactory',
@ -67,10 +69,10 @@ class Constants {

  static const List<Dependency> flutterPlugins = [
    Dependency(
-      name: 'Connectivity',
+      name: 'Connectivity Plus',
      license: 'BSD 3-Clause',
-      licenseUrl: 'https://github.com/flutter/plugins/blob/master/packages/connectivity/connectivity/LICENSE',
-      sourceUrl: 'https://github.com/flutter/plugins/blob/master/packages/connectivity/connectivity',
+      licenseUrl: 'https://github.com/fluttercommunity/plus_plugins/blob/main/packages/connectivity_plus/LICENSE',
+      sourceUrl: 'https://github.com/fluttercommunity/plus_plugins/tree/main/packages/connectivity_plus',
    ),
    Dependency(
      name: 'FlutterFire (Core, Analytics, Crashlytics)',
@ -79,7 +81,7 @@ class Constants {
      sourceUrl: 'https://github.com/FirebaseExtended/flutterfire',
    ),
    Dependency(
-      name: 'fijkplayer',
+      name: 'fijkplayer (Aves fork)',
      license: 'MIT',
      licenseUrl: 'https://github.com/deckerst/fijkplayer/blob/master/LICENSE',
      sourceUrl: 'https://github.com/deckerst/fijkplayer',
@ -97,10 +99,10 @@ class Constants {
      sourceUrl: 'https://github.com/flutter/plugins/blob/master/packages/google_maps_flutter/google_maps_flutter',
    ),
    Dependency(
-      name: 'Package Info',
+      name: 'Package Info Plus',
      license: 'BSD 3-Clause',
-      licenseUrl: 'https://github.com/flutter/plugins/blob/master/packages/package_info/LICENSE',
-      sourceUrl: 'https://github.com/flutter/plugins/tree/master/packages/package_info',
+      licenseUrl: 'https://github.com/fluttercommunity/plus_plugins/tree/main/packages/package_info_plus/LICENSE',
+      sourceUrl: 'https://github.com/fluttercommunity/plus_plugins/tree/main/packages/package_info_plus',
    ),
    Dependency(
      name: 'Permission Handler',
@ -127,10 +129,10 @@ class Constants {
      sourceUrl: 'https://github.com/tekartik/sqflite',
    ),
    Dependency(
-      name: 'Streams Channel',
+      name: 'Streams Channel (Aves fork)',
      license: 'Apache 2.0',
-      licenseUrl: 'https://github.com/loup-v/streams_channel/blob/master/LICENSE',
-      sourceUrl: 'https://github.com/loup-v/streams_channel',
+      licenseUrl: 'https://github.com/deckerst/aves_streams_channel/blob/master/LICENSE',
+      sourceUrl: 'https://github.com/deckerst/aves_streams_channel',
    ),
    Dependency(
      name: 'URL Launcher',
@ -229,7 +231,7 @@ class Constants {
      sourceUrl: 'https://github.com/benPesso/flutter_decorated_icon',
    ),
    Dependency(
-      name: 'Expansion Tile Card',
+      name: 'Expansion Tile Card (Aves fork)',
      license: 'BSD 3-Clause',
      licenseUrl: 'https://github.com/deckerst/expansion_tile_card/blob/master/LICENSE',
      sourceUrl: 'https://github.com/deckerst/expansion_tile_card',
@ -249,8 +251,8 @@ class Constants {
    Dependency(
      name: 'Flutter Markdown',
      license: 'BSD 3-Clause',
-      licenseUrl: 'https://github.com/flutter/flutter_markdown/blob/master/LICENSE',
-      sourceUrl: 'https://github.com/flutter/flutter_markdown',
+      licenseUrl: 'https://github.com/flutter/packages/blob/master/packages/flutter_markdown/LICENSE',
+      sourceUrl: 'https://github.com/flutter/packages/tree/master/packages/flutter_markdown',
    ),
    Dependency(
      name: 'Flutter Staggered Animations',
@ -310,9 +312,9 @@ class Dependency {
  final String licenseUrl;

  const Dependency({
-    @required this.name,
-    @required this.license,
-    @required this.licenseUrl,
-    @required this.sourceUrl,
+    required this.name,
+    required this.license,
+    required this.licenseUrl,
+    required this.sourceUrl,
  });
 }
--- a/lib/utils/debouncer.dart
+++ b/lib/utils/debouncer.dart
@ -5,11 +5,11 @@ import 'package:flutter/foundation.dart';
 class Debouncer {
  final Duration delay;

-  Timer _timer;
+  Timer? _timer;

-  Debouncer({@required this.delay});
+  Debouncer({required this.delay});

-  void call(Function action) {
+  void call(VoidCallback action) {
    _timer?.cancel();
    _timer = Timer(delay, action);
  }
--- a/lib/utils/math_utils.dart
+++ b/lib/utils/math_utils.dart
@ -1,7 +1,5 @@
 import 'dart:math';

-import 'package:flutter/foundation.dart';
-
 final double _log2 = log(2);
 const double _piOver180 = pi / 180.0;

@ -9,12 +7,12 @@ double toDegrees(num radians) => radians / _piOver180;

 double toRadians(num degrees) => degrees * _piOver180;

-int highestPowerOf2(num x) => x < 1 ? 0 : pow(2, (log(x) / _log2).floor());
+int highestPowerOf2(num x) => x < 1 ? 0 : pow(2, (log(x) / _log2).floor()) as int;

-double roundToPrecision(final double value, {@required final int decimals}) => (value * pow(10, decimals)).round() / pow(10, decimals);
+double roundToPrecision(final double value, {required final int decimals}) => (value * pow(10, decimals)).round() / pow(10, decimals);

 // e.g. x=12345, precision=3 should return 13000
 int ceilBy(num x, int precision) {
  final factor = pow(10, precision);
-  return (x / factor).ceil() * factor;
+  return (x / factor).ceil() * (factor as int);
 }
--- a/lib/utils/string_utils.dart
+++ b/lib/utils/string_utils.dart
@ -3,7 +3,7 @@ extension ExtraString on String {
  static final _sentenceCaseStep2 = RegExp(r'([a-z])([A-Z])');

  String toSentenceCase() {
-    var s = replaceFirstMapped(RegExp('.'), (m) => m.group(0).toUpperCase());
+    var s = replaceFirstMapped(RegExp('.'), (m) => m.group(0)!.toUpperCase());
    return s.replaceAllMapped(_sentenceCaseStep1, (m) => ' ${m.group(1)}').replaceAllMapped(_sentenceCaseStep2, (m) => '${m.group(1)} ${m.group(2)}').trim();
  }
 }
--- a/lib/utils/time_utils.dart
+++ b/lib/utils/time_utils.dart
@ -15,15 +15,15 @@ String formatPreciseDuration(Duration d) {
 }

 extension ExtraDateTime on DateTime {
-  bool isAtSameYearAs(DateTime other) => this?.year == other?.year;
+  bool isAtSameYearAs(DateTime? other) => year == other?.year;

-  bool isAtSameMonthAs(DateTime other) => isAtSameYearAs(other) && this?.month == other?.month;
+  bool isAtSameMonthAs(DateTime? other) => isAtSameYearAs(other) && month == other?.month;

-  bool isAtSameDayAs(DateTime other) => isAtSameMonthAs(other) && this?.day == other?.day;
+  bool isAtSameDayAs(DateTime? other) => isAtSameMonthAs(other) && day == other?.day;

  bool get isToday => isAtSameDayAs(DateTime.now());

-  bool get isYesterday => isAtSameDayAs(DateTime.now().subtract(Duration(days: 1)));
+  bool get isYesterday => isAtSameDayAs(DateTime.now().subtract(const Duration(days: 1)));

  bool get isThisMonth => isAtSameMonthAs(DateTime.now());

--- a/lib/widgets/about/about_page.dart
+++ b/lib/widgets/about/about_page.dart
@ -18,15 +18,15 @@ class AboutPage extends StatelessWidget {
        child: CustomScrollView(
          slivers: [
            SliverPadding(
-              padding: EdgeInsets.only(top: 16),
+              padding: const EdgeInsets.only(top: 16),
              sliver: SliverList(
                delegate: SliverChildListDelegate(
                  [
                    AppReference(),
-                    Divider(),
+                    const Divider(),
                    AboutUpdate(),
                    AboutCredits(),
-                    Divider(),
+                    const Divider(),
                  ],
                ),
              ),
--- a/lib/widgets/about/app_ref.dart
+++ b/lib/widgets/about/app_ref.dart
@ -5,7 +5,7 @@ import 'package:aves/widgets/common/basic/link_chip.dart';
 import 'package:aves/widgets/common/extensions/build_context.dart';
 import 'package:aves/widgets/common/identity/aves_logo.dart';
 import 'package:flutter/material.dart';
-import 'package:package_info/package_info.dart';
+import 'package:package_info_plus/package_info_plus.dart';

 class AppReference extends StatefulWidget {
  @override
@ -13,7 +13,7 @@ class AppReference extends StatefulWidget {
 }

 class _AppReferenceState extends State<AppReference> {
-  Future<PackageInfo> _packageInfoLoader;
+  late Future<PackageInfo> _packageInfoLoader;

  @override
  void initState() {
@ -28,14 +28,14 @@ class _AppReferenceState extends State<AppReference> {
        children: [
          _buildAvesLine(),
          _buildFlutterLine(),
-          SizedBox(height: 16),
+          const SizedBox(height: 16),
        ],
      ),
    );
  }

  Widget _buildAvesLine() {
-    final style = TextStyle(
+    const style = TextStyle(
      fontSize: 20,
      fontWeight: FontWeight.normal,
      letterSpacing: 1.0,
@ -47,7 +47,7 @@ class _AppReferenceState extends State<AppReference> {
      builder: (context, snapshot) {
        return LinkChip(
          leading: AvesLogo(
-            size: style.fontSize * MediaQuery.textScaleFactorOf(context) * 1.25,
+            size: style.fontSize! * MediaQuery.textScaleFactorOf(context) * 1.25,
          ),
          text: '${context.l10n.appName} ${snapshot.data?.version}',
          url: 'https://github.com/deckerst/aves',
@ -59,16 +59,16 @@ class _AppReferenceState extends State<AppReference> {

  Widget _buildFlutterLine() {
    final style = DefaultTextStyle.of(context).style;
-    final subColor = style.color.withOpacity(.6);
+    final subColor = style.color!.withOpacity(.6);

    return Text.rich(
      TextSpan(
        children: [
          WidgetSpan(
            child: Padding(
-              padding: EdgeInsetsDirectional.only(end: 4),
+              padding: const EdgeInsetsDirectional.only(end: 4),
              child: FlutterLogo(
-                size: style.fontSize * 1.25,
+                size: style.fontSize! * 1.25,
              ),
            ),
          ),
--- a/lib/widgets/about/credits.dart
+++ b/lib/widgets/about/credits.dart
@ -9,12 +9,12 @@ class AboutCredits extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Padding(
-      padding: EdgeInsets.symmetric(horizontal: 16),
+      padding: const EdgeInsets.symmetric(horizontal: 16),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          ConstrainedBox(
-            constraints: BoxConstraints(minHeight: 48),
+            constraints: const BoxConstraints(minHeight: 48),
            child: Align(
              alignment: AlignmentDirectional.centerStart,
              child: Text(context.l10n.aboutCredits, style: Constants.titleTextStyle),
@ -24,7 +24,7 @@ class AboutCredits extends StatelessWidget {
            TextSpan(
              children: [
                TextSpan(text: context.l10n.aboutCreditsWorldAtlas1),
-                WidgetSpan(
+                const WidgetSpan(
                  child: LinkChip(
                    text: 'World Atlas',
                    url: 'https://github.com/topojson/world-atlas',
@ -36,7 +36,7 @@ class AboutCredits extends StatelessWidget {
              ],
            ),
          ),
-          SizedBox(height: 16),
+          const SizedBox(height: 16),
        ],
      ),
    );
--- a/lib/widgets/about/licenses.dart
+++ b/lib/widgets/about/licenses.dart
@ -12,8 +12,8 @@ class Licenses extends StatefulWidget {
 }

 class _LicensesState extends State<Licenses> {
-  final ValueNotifier<String> _expandedNotifier = ValueNotifier(null);
-  List<Dependency> _platform, _flutterPlugins, _flutterPackages, _dartPackages;
+  final ValueNotifier<String?> _expandedNotifier = ValueNotifier(null);
+  late List<Dependency> _platform, _flutterPlugins, _flutterPackages, _dartPackages;

  @override
  void initState() {
@ -36,12 +36,12 @@ class _LicensesState extends State<Licenses> {
  @override
  Widget build(BuildContext context) {
    return SliverPadding(
-      padding: EdgeInsets.symmetric(horizontal: 8),
+      padding: const EdgeInsets.symmetric(horizontal: 8),
      sliver: SliverList(
        delegate: SliverChildListDelegate(
          [
            _buildHeader(),
-            SizedBox(height: 16),
+            const SizedBox(height: 16),
            AvesExpansionTile(
              title: context.l10n.aboutLicensesAndroidLibraries,
              color: BrandColors.android,
@ -76,7 +76,7 @@ class _LicensesState extends State<Licenses> {
                        // as of Flutter v1.22.4, `cardColor` is used as a background color by `LicensePage`
                        cardColor: Theme.of(context).scaffoldBackgroundColor,
                      ),
-                      child: LicensePage(),
+                      child: const LicensePage(),
                    ),
                  ),
                ),
@ -91,18 +91,18 @@ class _LicensesState extends State<Licenses> {

  Widget _buildHeader() {
    return Padding(
-      padding: EdgeInsets.symmetric(horizontal: 8),
+      padding: const EdgeInsets.symmetric(horizontal: 8),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          ConstrainedBox(
-            constraints: BoxConstraints(minHeight: 48),
+            constraints: const BoxConstraints(minHeight: 48),
            child: Align(
              alignment: AlignmentDirectional.centerStart,
              child: Text(context.l10n.aboutLicenses, style: Constants.titleTextStyle),
            ),
          ),
-          SizedBox(height: 8),
+          const SizedBox(height: 8),
          Text(context.l10n.aboutLicensesBanner),
        ],
      ),
@ -118,21 +118,21 @@ class LicenseRow extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final textTheme = Theme.of(context).textTheme;
-    final bodyTextStyle = textTheme.bodyText2;
-    final subColor = bodyTextStyle.color.withOpacity(.6);
+    final bodyTextStyle = textTheme.bodyText2!;
+    final subColor = bodyTextStyle.color!.withOpacity(.6);

    return Padding(
-      padding: EdgeInsets.symmetric(vertical: 8),
+      padding: const EdgeInsets.symmetric(vertical: 8),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          LinkChip(
            text: package.name,
            url: package.sourceUrl,
-            textStyle: TextStyle(fontWeight: FontWeight.bold),
+            textStyle: const TextStyle(fontWeight: FontWeight.bold),
          ),
          Padding(
-            padding: EdgeInsetsDirectional.only(start: 16),
+            padding: const EdgeInsetsDirectional.only(start: 16),
            child: LinkChip(
              text: package.license,
              url: package.licenseUrl,
--- a/lib/widgets/about/news_badge.dart
+++ b/lib/widgets/about/news_badge.dart
@ -1,9 +1,11 @@
 import 'package:flutter/material.dart';

 class AboutNewsBadge extends StatelessWidget {
+  const AboutNewsBadge();
+
  @override
  Widget build(BuildContext context) {
-    return Icon(
+    return const Icon(
      Icons.circle,
      size: 12,
      color: Colors.red,
--- a/lib/widgets/about/update.dart
+++ b/lib/widgets/about/update.dart
@ -11,7 +11,7 @@ class AboutUpdate extends StatefulWidget {
 }

 class _AboutUpdateState extends State<AboutUpdate> {
-  Future<bool> _updateChecker;
+  late Future<bool> _updateChecker;

  @override
  void initState() {
@ -25,22 +25,22 @@ class _AboutUpdateState extends State<AboutUpdate> {
      future: _updateChecker,
      builder: (context, snapshot) {
        final newVersionAvailable = snapshot.data == true;
-        if (!newVersionAvailable) return SizedBox();
+        if (!newVersionAvailable) return const SizedBox();
        return Column(
          children: [
            Padding(
-              padding: EdgeInsets.symmetric(horizontal: 16),
+              padding: const EdgeInsets.symmetric(horizontal: 16),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  ConstrainedBox(
-                    constraints: BoxConstraints(minHeight: 48),
+                    constraints: const BoxConstraints(minHeight: 48),
                    child: Align(
                      alignment: AlignmentDirectional.centerStart,
                      child: Text.rich(
                        TextSpan(
                          children: [
-                            WidgetSpan(
+                            const WidgetSpan(
                              child: Padding(
                                padding: EdgeInsetsDirectional.only(end: 8),
                                child: AboutNewsBadge(),
@ -61,7 +61,7 @@ class _AboutUpdateState extends State<AboutUpdate> {
                          child: LinkChip(
                            text: context.l10n.aboutUpdateGithub,
                            url: 'https://github.com/deckerst/aves/releases',
-                            textStyle: TextStyle(fontWeight: FontWeight.bold),
+                            textStyle: const TextStyle(fontWeight: FontWeight.bold),
                          ),
                          alignment: PlaceholderAlignment.middle,
                        ),
@ -70,7 +70,7 @@ class _AboutUpdateState extends State<AboutUpdate> {
                          child: LinkChip(
                            text: context.l10n.aboutUpdateGooglePlay,
                            url: 'https://play.google.com/store/apps/details?id=deckers.thibault.aves',
-                            textStyle: TextStyle(fontWeight: FontWeight.bold),
+                            textStyle: const TextStyle(fontWeight: FontWeight.bold),
                          ),
                          alignment: PlaceholderAlignment.middle,
                        ),
@ -78,11 +78,11 @@ class _AboutUpdateState extends State<AboutUpdate> {
                      ],
                    ),
                  ),
-                  SizedBox(height: 16),
+                  const SizedBox(height: 16),
                ],
              ),
            ),
-            Divider(),
+            const Divider(),
          ],
        );
      },
--- a/lib/widgets/aves_app.dart
+++ b/lib/widgets/aves_app.dart
@ -0,0 +1,173 @@
+import 'dart:ui';
+
+import 'package:aves/app_mode.dart';
+import 'package:aves/model/settings/settings.dart';
+import 'package:aves/model/source/collection_source.dart';
+import 'package:aves/model/source/media_store_source.dart';
+import 'package:aves/services/services.dart';
+import 'package:aves/theme/durations.dart';
+import 'package:aves/theme/icons.dart';
+import 'package:aves/theme/themes.dart';
+import 'package:aves/utils/debouncer.dart';
+import 'package:aves/widgets/common/behaviour/route_tracker.dart';
+import 'package:aves/widgets/common/behaviour/routes.dart';
+import 'package:aves/widgets/common/extensions/build_context.dart';
+import 'package:aves/widgets/common/providers/highlight_info_provider.dart';
+import 'package:aves/widgets/home_page.dart';
+import 'package:aves/widgets/welcome_page.dart';
+import 'package:firebase_analytics/firebase_analytics.dart';
+import 'package:firebase_analytics/observer.dart';
+import 'package:firebase_core/firebase_core.dart';
+import 'package:firebase_crashlytics/firebase_crashlytics.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+import 'package:overlay_support/overlay_support.dart';
+import 'package:provider/provider.dart';
+
+class AvesApp extends StatefulWidget {
+  @override
+  _AvesAppState createState() => _AvesAppState();
+}
+
+class _AvesAppState extends State<AvesApp> {
+  final ValueNotifier<AppMode> appModeNotifier = ValueNotifier(AppMode.main);
+  late Future<void> _appSetup;
+  final _mediaStoreSource = MediaStoreSource();
+  final Debouncer _contentChangeDebouncer = Debouncer(delay: Durations.contentChangeDebounceDelay);
+  final Set<String> changedUris = {};
+
+  // observers are not registered when using the same list object with different items
+  // the list itself needs to be reassigned
+  List<NavigatorObserver> _navigatorObservers = [];
+  final EventChannel _contentChangeChannel = const EventChannel('deckers.thibault/aves/contentchange');
+  final EventChannel _newIntentChannel = const EventChannel('deckers.thibault/aves/intent');
+  final GlobalKey<NavigatorState> _navigatorKey = GlobalKey(debugLabel: 'app-navigator');
+
+  Widget getFirstPage({Map? intentData}) => settings.hasAcceptedTerms ? HomePage(intentData: intentData) : const WelcomePage();
+
+  @override
+  void initState() {
+    super.initState();
+    initPlatformServices();
+    _appSetup = _setup();
+    _contentChangeChannel.receiveBroadcastStream().listen((event) => _onContentChange(event as String?));
+    _newIntentChannel.receiveBroadcastStream().listen((event) => _onNewIntent(event as Map?));
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    // place the settings provider above `MaterialApp`
+    // so it can be used during navigation transitions
+    return ChangeNotifierProvider<Settings>.value(
+      value: settings,
+      child: ListenableProvider<ValueNotifier<AppMode>>.value(
+        value: appModeNotifier,
+        child: Provider<CollectionSource>.value(
+          value: _mediaStoreSource,
+          child: HighlightInfoProvider(
+            child: OverlaySupport(
+              child: FutureBuilder<void>(
+                future: _appSetup,
+                builder: (context, snapshot) {
+                  final initialized = !snapshot.hasError && snapshot.connectionState == ConnectionState.done;
+                  final home = initialized
+                      ? getFirstPage()
+                      : Scaffold(
+                          body: snapshot.hasError ? _buildError(snapshot.error!) : const SizedBox(),
+                        );
+                  return Selector<Settings, Locale?>(
+                      selector: (context, s) => s.locale,
+                      builder: (context, settingsLocale, child) {
+                        return MaterialApp(
+                          navigatorKey: _navigatorKey,
+                          home: home,
+                          navigatorObservers: _navigatorObservers,
+                          onGenerateTitle: (context) => context.l10n.appName,
+                          darkTheme: Themes.darkTheme,
+                          themeMode: ThemeMode.dark,
+                          locale: settingsLocale,
+                          localizationsDelegates: [
+                            ...AppLocalizations.localizationsDelegates,
+                          ],
+                          supportedLocales: AppLocalizations.supportedLocales,
+                          // checkerboardRasterCacheImages: true,
+                          // checkerboardOffscreenLayers: true,
+                        );
+                      });
+                },
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildError(Object error) {
+    return Container(
+      alignment: Alignment.center,
+      padding: const EdgeInsets.all(16),
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          const Icon(AIcons.error),
+          const SizedBox(height: 16),
+          Text(error.toString()),
+        ],
+      ),
+    );
+  }
+
+  Future<void> _setup() async {
+    await Firebase.initializeApp().then((app) {
+      final crashlytics = FirebaseCrashlytics.instance;
+      FlutterError.onError = crashlytics.recordFlutterError;
+      crashlytics.setCustomKey('locales', window.locales.join(', '));
+      final now = DateTime.now();
+      crashlytics.setCustomKey('timezone', '${now.timeZoneName} (${now.timeZoneOffset})');
+      crashlytics.setCustomKey(
+          'build_mode',
+          kReleaseMode
+              ? 'release'
+              : kProfileMode
+                  ? 'profile'
+                  : 'debug');
+    });
+    await settings.init();
+    await settings.initFirebase();
+    _navigatorObservers = [
+      FirebaseAnalyticsObserver(analytics: FirebaseAnalytics()),
+      CrashlyticsRouteTracker(),
+    ];
+  }
+
+  void _onNewIntent(Map? intentData) {
+    debugPrint('$runtimeType onNewIntent with intentData=$intentData');
+
+    // do not reset when relaunching the app
+    if (appModeNotifier.value == AppMode.main && (intentData == null || intentData.isEmpty == true)) return;
+
+    FirebaseCrashlytics.instance.log('New intent');
+    _navigatorKey.currentState!.pushReplacement(DirectMaterialPageRoute(
+      settings: const RouteSettings(name: HomePage.routeName),
+      builder: (_) => getFirstPage(intentData: intentData),
+    ));
+  }
+
+  void _onContentChange(String? uri) {
+    if (uri != null) changedUris.add(uri);
+    if (changedUris.isNotEmpty) {
+      _contentChangeDebouncer(() async {
+        final todo = changedUris.toSet();
+        changedUris.clear();
+        final tempUris = await _mediaStoreSource.refreshUris(todo);
+        if (tempUris.isNotEmpty) {
+          changedUris.addAll(tempUris);
+          _onContentChange(null);
+        }
+      });
+    }
+  }
+}
--- a/lib/widgets/collection/app_bar.dart
+++ b/lib/widgets/collection/app_bar.dart
@ -35,9 +35,9 @@ class CollectionAppBar extends StatefulWidget {
  final CollectionLens collection;

  const CollectionAppBar({
-    Key key,
-    @required this.appBarHeightNotifier,
-    @required this.collection,
+    Key? key,
+    required this.appBarHeightNotifier,
+    required this.collection,
  }) : super(key: key);

  @override
@ -46,9 +46,9 @@ class CollectionAppBar extends StatefulWidget {

 class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerProviderStateMixin {
  final TextEditingController _searchFieldController = TextEditingController();
-  EntrySetActionDelegate _actionDelegate;
-  AnimationController _browseToSelectAnimation;
-  Future<bool> _canAddShortcutsLoader;
+  final EntrySetActionDelegate _actionDelegate = EntrySetActionDelegate();
+  late AnimationController _browseToSelectAnimation;
+  late Future<bool> _canAddShortcutsLoader;

  CollectionLens get collection => widget.collection;

@ -59,16 +59,13 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
  @override
  void initState() {
    super.initState();
-    _actionDelegate = EntrySetActionDelegate(
-      collection: collection,
-    );
    _browseToSelectAnimation = AnimationController(
      duration: Durations.iconAnimation,
      vsync: this,
    );
    _canAddShortcutsLoader = AppShortcutService.canPin();
    _registerWidget(widget);
-    WidgetsBinding.instance.addPostFrameCallback((_) => _updateHeight());
+    WidgetsBinding.instance!.addPostFrameCallback((_) => _updateHeight());
  }

  @override
@ -127,8 +124,8 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
  }

  Widget _buildAppBarLeading() {
-    VoidCallback onPressed;
-    String tooltip;
+    VoidCallback? onPressed;
+    String? tooltip;
    if (collection.isBrowsing) {
      onPressed = Scaffold.of(context).openDrawer;
      tooltip = MaterialLocalizations.of(context).openAppDrawerTooltip;
@ -137,7 +134,7 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
      tooltip = MaterialLocalizations.of(context).backButtonTooltip;
    }
    return IconButton(
-      key: Key('appbar-leading-button'),
+      key: const Key('appbar-leading-button'),
      icon: AnimatedIcon(
        icon: AnimatedIcons.menu_arrow,
        progress: _browseToSelectAnimation,
@ -147,7 +144,7 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
    );
  }

-  Widget _buildAppBarTitle() {
+  Widget? _buildAppBarTitle() {
    if (collection.isBrowsing) {
      final appMode = context.watch<ValueNotifier<AppMode>>().value;
      Widget title = Text(appMode.isPicking ? context.l10n.collectionPickPageTitle : context.l10n.collectionPageTitle);
@ -197,19 +194,19 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
        builder: (context, snapshot) {
          final canAddShortcuts = snapshot.data ?? false;
          return PopupMenuButton<CollectionAction>(
-            key: Key('appbar-menu-button'),
+            key: const Key('appbar-menu-button'),
            itemBuilder: (context) {
              final isNotEmpty = !collection.isEmpty;
              final hasSelection = collection.selection.isNotEmpty;
              return [
                PopupMenuItem(
-                  key: Key('menu-sort'),
+                  key: const Key('menu-sort'),
                  value: CollectionAction.sort,
                  child: MenuRow(text: context.l10n.menuActionSort, icon: AIcons.sort),
                ),
                if (collection.sortFactor == EntrySortFactor.date)
                  PopupMenuItem(
-                    key: Key('menu-group'),
+                    key: const Key('menu-group'),
                    value: CollectionAction.group,
                    child: MenuRow(text: context.l10n.menuActionGroup, icon: AIcons.group),
                  ),
@ -231,7 +228,7 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
                    ),
                ],
                if (collection.isSelecting) ...[
-                  PopupMenuDivider(),
+                  const PopupMenuDivider(),
                  PopupMenuItem(
                    value: CollectionAction.copy,
                    enabled: hasSelection,
@ -247,7 +244,7 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
                    enabled: hasSelection,
                    child: MenuRow(text: context.l10n.collectionActionRefreshMetadata),
                  ),
-                  PopupMenuDivider(),
+                  const PopupMenuDivider(),
                  PopupMenuItem(
                    value: CollectionAction.selectAll,
                    enabled: collection.selection.length < collection.entryCount,
@ -359,17 +356,18 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
      final sortedFilters = List<CollectionFilter>.from(filters)..sort();
      defaultName = sortedFilters.first.getLabel(context);
    }
-    final result = await showDialog<Tuple2<AvesEntry, String>>(
+    final result = await showDialog<Tuple2<AvesEntry?, String>>(
      context: context,
      builder: (context) => AddShortcutDialog(
        collection: collection,
-        defaultName: defaultName,
+        defaultName: defaultName ?? '',
      ),
    );
+    if (result == null) return;
+
    final coverEntry = result.item1;
    final name = result.item2;
-
-    if (name == null || name.isEmpty) return;
+    if (name.isEmpty) return;

    unawaited(AppShortcutService.pin(name, coverEntry, filters));
  }
@ -389,7 +387,7 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
    Navigator.push(
      context,
      MaterialPageRoute(
-        settings: RouteSettings(name: StatsPage.routeName),
+        settings: const RouteSettings(name: StatsPage.routeName),
        builder: (context) => StatsPage(
          source: source,
          parentCollection: collection,
--- a/lib/widgets/collection/collection_grid.dart
+++ b/lib/widgets/collection/collection_grid.dart
@ -4,7 +4,6 @@ import 'package:aves/app_mode.dart';
 import 'package:aves/model/entry.dart';
 import 'package:aves/model/filters/favourite.dart';
 import 'package:aves/model/filters/mime.dart';
-import 'package:aves/model/highlight.dart';
 import 'package:aves/model/source/collection_lens.dart';
 import 'package:aves/model/source/enums.dart';
 import 'package:aves/ref/mime_types.dart';
@ -22,7 +21,7 @@ import 'package:aves/widgets/common/basic/insets.dart';
 import 'package:aves/widgets/common/behaviour/sloppy_scroll_physics.dart';
 import 'package:aves/widgets/common/extensions/build_context.dart';
 import 'package:aves/widgets/common/extensions/media_query.dart';
-import 'package:aves/widgets/common/grid/section_layout.dart';
+import 'package:aves/widgets/common/grid/item_tracker.dart';
 import 'package:aves/widgets/common/grid/sliver.dart';
 import 'package:aves/widgets/common/identity/empty.dart';
 import 'package:aves/widgets/common/identity/scroll_thumb.dart';
@ -35,29 +34,30 @@ import 'package:provider/provider.dart';
 import 'package:tuple/tuple.dart';

 class CollectionGrid extends StatefulWidget {
-  final String settingsRouteKey;
+  final String? settingsRouteKey;

  const CollectionGrid({
+    Key? key,
    this.settingsRouteKey,
-  });
+  }) : super(key: key);

  @override
  _CollectionGridState createState() => _CollectionGridState();
 }

 class _CollectionGridState extends State<CollectionGrid> {
-  TileExtentController _tileExtentController;
+  TileExtentController? _tileExtentController;

  @override
  Widget build(BuildContext context) {
    _tileExtentController ??= TileExtentController(
-      settingsRouteKey: widget.settingsRouteKey ?? context.currentRouteName,
+      settingsRouteKey: widget.settingsRouteKey ?? context.currentRouteName!,
      columnCountDefault: 4,
      extentMin: 46,
-      spacing: 0,
+      spacing: 2,
    );
    return TileExtentControllerProvider(
-      controller: _tileExtentController,
+      controller: _tileExtentController!,
      child: _CollectionGridContent(),
    );
  }
@ -75,19 +75,21 @@ class _CollectionGridContent extends StatelessWidget {
          builder: (context, tileExtent, child) {
            return ThumbnailTheme(
              extent: tileExtent,
-              child: Selector<TileExtentController, Tuple2<double, int>>(
-                selector: (context, c) => Tuple2(c.viewportSize.width, c.columnCount),
+              child: Selector<TileExtentController, Tuple3<double, int, double>>(
+                selector: (context, c) => Tuple3(c.viewportSize.width, c.columnCount, c.spacing),
                builder: (context, c, child) {
                  final scrollableWidth = c.item1;
                  final columnCount = c.item2;
+                  final tileSpacing = c.item3;
                  // do not listen for animation delay change
                  final controller = Provider.of<TileExtentController>(context, listen: false);
                  final tileAnimationDelay = controller.getTileAnimationDelay(Durations.staggeredAnimationPageTarget);
                  return SectionedEntryListLayoutProvider(
                    collection: collection,
                    scrollableWidth: scrollableWidth,
-                    tileExtent: tileExtent,
                    columnCount: columnCount,
+                    spacing: tileSpacing,
+                    tileExtent: tileExtent,
                    tileBuilder: (entry) => InteractiveThumbnail(
                      key: ValueKey(entry.contentId),
                      collection: collection,
@ -99,7 +101,7 @@ class _CollectionGridContent extends StatelessWidget {
                    child: _CollectionSectionedContent(
                      collection: collection,
                      isScrollingNotifier: _isScrollingNotifier,
-                      scrollController: PrimaryScrollController.of(context),
+                      scrollController: PrimaryScrollController.of(context)!,
                    ),
                  );
                },
@ -119,42 +121,46 @@ class _CollectionSectionedContent extends StatefulWidget {
  final ScrollController scrollController;

  const _CollectionSectionedContent({
-    @required this.collection,
-    @required this.isScrollingNotifier,
-    @required this.scrollController,
+    required this.collection,
+    required this.isScrollingNotifier,
+    required this.scrollController,
  });

  @override
  _CollectionSectionedContentState createState() => _CollectionSectionedContentState();
 }

-class _CollectionSectionedContentState extends State<_CollectionSectionedContent> {
+class _CollectionSectionedContentState extends State<_CollectionSectionedContent> with WidgetsBindingObserver, GridItemTrackerMixin<AvesEntry, _CollectionSectionedContent> {
  CollectionLens get collection => widget.collection;

+  @override
  ScrollController get scrollController => widget.scrollController;

-  final ValueNotifier<double> _appBarHeightNotifier = ValueNotifier(0);
-  final GlobalKey _scrollableKey = GlobalKey(debugLabel: 'thumbnail-collection-scrollable');
+  @override
+  final ValueNotifier<double> appBarHeightNotifier = ValueNotifier(0);
+
+  @override
+  final GlobalKey scrollableKey = GlobalKey(debugLabel: 'thumbnail-collection-scrollable');

  @override
  Widget build(BuildContext context) {
    final scrollView = AnimationLimiter(
      child: _CollectionScrollView(
-        scrollableKey: _scrollableKey,
+        scrollableKey: scrollableKey,
        collection: collection,
        appBar: CollectionAppBar(
-          appBarHeightNotifier: _appBarHeightNotifier,
+          appBarHeightNotifier: appBarHeightNotifier,
          collection: collection,
        ),
-        appBarHeightNotifier: _appBarHeightNotifier,
+        appBarHeightNotifier: appBarHeightNotifier,
        isScrollingNotifier: widget.isScrollingNotifier,
        scrollController: scrollController,
      ),
    );

    final scaler = _CollectionScaler(
-      scrollableKey: _scrollableKey,
-      appBarHeightNotifier: _appBarHeightNotifier,
+      scrollableKey: scrollableKey,
+      appBarHeightNotifier: appBarHeightNotifier,
      child: scrollView,
    );

@ -163,7 +169,7 @@ class _CollectionSectionedContentState extends State<_CollectionSectionedContent
      selectable: isMainMode,
      collection: collection,
      scrollController: scrollController,
-      appBarHeightNotifier: _appBarHeightNotifier,
+      appBarHeightNotifier: appBarHeightNotifier,
      child: scaler,
    );

@ -177,9 +183,9 @@ class _CollectionScaler extends StatelessWidget {
  final Widget child;

  const _CollectionScaler({
-    @required this.scrollableKey,
-    @required this.appBarHeightNotifier,
-    @required this.child,
+    required this.scrollableKey,
+    required this.appBarHeightNotifier,
+    required this.child,
  });

  @override
@ -187,15 +193,13 @@ class _CollectionScaler extends StatelessWidget {
    final tileSpacing = context.select<TileExtentController, double>((controller) => controller.spacing);
    return GridScaleGestureDetector<AvesEntry>(
      scrollableKey: scrollableKey,
-      appBarHeightNotifier: appBarHeightNotifier,
      gridBuilder: (center, extent, child) => CustomPaint(
-        // painting the thumbnail half-border on top of the grid yields artifacts,
-        // so we use a `foregroundPainter` to cover them instead
-        foregroundPainter: GridPainter(
+        painter: GridPainter(
          center: center,
          extent: extent,
          spacing: tileSpacing,
-          strokeWidth: DecoratedThumbnail.borderWidth * 2,
+          borderWidth: DecoratedThumbnail.borderWidth,
+          borderRadius: Radius.zero,
          color: DecoratedThumbnail.borderColor,
        ),
        child: child,
@ -204,16 +208,11 @@ class _CollectionScaler extends StatelessWidget {
        extent: extent,
        child: DecoratedThumbnail(
          entry: entry,
-          extent: extent,
+          tileExtent: context.read<TileExtentController>().effectiveExtentMax,
          selectable: false,
          highlightable: false,
        ),
      ),
-      getScaledItemTileRect: (context, entry) {
-        final sectionedListLayout = context.read<SectionedListLayout<AvesEntry>>();
-        return sectionedListLayout.getTileRect(entry) ?? Rect.zero;
-      },
-      onScaled: (entry) => context.read<HighlightInfo>().set(entry),
      child: child,
    );
  }
@ -228,12 +227,12 @@ class _CollectionScrollView extends StatefulWidget {
  final ScrollController scrollController;

  const _CollectionScrollView({
-    @required this.scrollableKey,
-    @required this.collection,
-    @required this.appBar,
-    @required this.appBarHeightNotifier,
-    @required this.isScrollingNotifier,
-    @required this.scrollController,
+    required this.scrollableKey,
+    required this.collection,
+    required this.appBar,
+    required this.appBarHeightNotifier,
+    required this.isScrollingNotifier,
+    required this.scrollController,
  });

  @override
@ -241,7 +240,7 @@ class _CollectionScrollView extends StatefulWidget {
 }

 class _CollectionScrollViewState extends State<_CollectionScrollView> {
-  Timer _scrollMonitoringTimer;
+  Timer? _scrollMonitoringTimer;

  @override
  void initState() {
@ -316,8 +315,8 @@ class _CollectionScrollViewState extends State<_CollectionScrollView> {
      primary: true,
      // workaround to prevent scrolling the app bar away
      // when there is no content and we use `SliverFillRemaining`
-      physics: collection.isEmpty ? NeverScrollableScrollPhysics() : SloppyScrollPhysics(parent: AlwaysScrollableScrollPhysics()),
-      cacheExtent: context.select<TileExtentController, double>((controller) => controller.effectiveExtentMax * 2),
+      physics: collection.isEmpty ? const NeverScrollableScrollPhysics() : const SloppyScrollPhysics(parent: AlwaysScrollableScrollPhysics()),
+      cacheExtent: context.select<TileExtentController, double>((controller) => controller.effectiveExtentMax),
      slivers: [
        appBar,
        collection.isEmpty
@ -336,7 +335,7 @@ class _CollectionScrollViewState extends State<_CollectionScrollView> {
      valueListenable: collection.source.stateNotifier,
      builder: (context, sourceState, child) {
        if (sourceState == SourceState.loading) {
-          return SizedBox.shrink();
+          return const SizedBox.shrink();
        }
        if (collection.filters.any((filter) => filter is FavouriteFilter)) {
          return EmptyContent(
--- a/lib/widgets/collection/collection_page.dart
+++ b/lib/widgets/collection/collection_page.dart
@ -46,7 +46,9 @@ class _CollectionPageState extends State<CollectionPage> {
                bottom: false,
                child: ChangeNotifierProvider<CollectionLens>.value(
                  value: collection,
-                  child: CollectionGrid(),
+                  child: const CollectionGrid(
+                    key: Key('collection-grid'),
+                  ),
                ),
              ),
            ),
--- a/lib/widgets/collection/draggable_thumb_label.dart
+++ b/lib/widgets/collection/draggable_thumb_label.dart
@ -13,8 +13,8 @@ class CollectionDraggableThumbLabel extends StatelessWidget {
  final double offsetY;

  const CollectionDraggableThumbLabel({
-    @required this.collection,
-    @required this.offsetY,
+    required this.collection,
+    required this.offsetY,
  });

  @override
@ -28,7 +28,7 @@ class CollectionDraggableThumbLabel extends StatelessWidget {
              case EntryGroupFactor.album:
                return [
                  DraggableThumbLabel.formatMonthThumbLabel(context, entry.bestDate),
-                  if (_hasMultipleSections(context)) context.read<CollectionSource>().getAlbumDisplayName(context, entry.directory),
+                  if (_showAlbumName(context, entry)) _getAlbumName(context, entry),
                ];
              case EntryGroupFactor.month:
              case EntryGroupFactor.none:
@ -40,21 +40,23 @@ class CollectionDraggableThumbLabel extends StatelessWidget {
                  DraggableThumbLabel.formatDayThumbLabel(context, entry.bestDate),
                ];
            }
-            break;
          case EntrySortFactor.name:
            return [
-              if (_hasMultipleSections(context)) context.read<CollectionSource>().getAlbumDisplayName(context, entry.directory),
-              entry.bestTitle,
+              if (_showAlbumName(context, entry)) _getAlbumName(context, entry),
+              if (entry.bestTitle != null) entry.bestTitle!,
            ];
          case EntrySortFactor.size:
            return [
-              formatFilesize(entry.sizeBytes, round: 0),
+              if (entry.sizeBytes != null) formatFilesize(entry.sizeBytes!, round: 0),
            ];
        }
-        return [];
      },
    );
  }

  bool _hasMultipleSections(BuildContext context) => context.read<SectionedListLayout<AvesEntry>>().sections.length > 1;
+
+  bool _showAlbumName(BuildContext context, AvesEntry entry) => _hasMultipleSections(context) && entry.directory != null;
+
+  String _getAlbumName(BuildContext context, AvesEntry entry) => context.read<CollectionSource>().getAlbumDisplayName(context, entry.directory!);
 }
--- a/lib/widgets/collection/entry_set_action_delegate.dart
+++ b/lib/widgets/collection/entry_set_action_delegate.dart
@ -3,41 +3,36 @@ import 'dart:async';
 import 'package:aves/model/actions/collection_actions.dart';
 import 'package:aves/model/actions/entry_actions.dart';
 import 'package:aves/model/actions/move_type.dart';
-import 'package:aves/model/entry.dart';
+import 'package:aves/model/filters/album.dart';
+import 'package:aves/model/highlight.dart';
 import 'package:aves/model/source/collection_lens.dart';
-import 'package:aves/model/source/collection_source.dart';
 import 'package:aves/services/android_app_service.dart';
 import 'package:aves/services/image_op_events.dart';
 import 'package:aves/services/services.dart';
+import 'package:aves/theme/durations.dart';
 import 'package:aves/utils/android_file_utils.dart';
+import 'package:aves/widgets/collection/collection_page.dart';
 import 'package:aves/widgets/common/action_mixins/feedback.dart';
 import 'package:aves/widgets/common/action_mixins/permission_aware.dart';
 import 'package:aves/widgets/common/action_mixins/size_aware.dart';
 import 'package:aves/widgets/common/extensions/build_context.dart';
 import 'package:aves/widgets/dialogs/aves_dialog.dart';
 import 'package:aves/widgets/filter_grids/album_pick.dart';
-import 'package:flutter/foundation.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
+import 'package:pedantic/pedantic.dart';
+import 'package:provider/provider.dart';

 class EntrySetActionDelegate with FeedbackMixin, PermissionAwareMixin, SizeAwareMixin {
-  final CollectionLens collection;
-
-  CollectionSource get source => collection.source;
-
-  Set<AvesEntry> get selection => collection.selection;
-
-  EntrySetActionDelegate({
-    @required this.collection,
-  });
-
  void onEntryActionSelected(BuildContext context, EntryAction action) {
    switch (action) {
      case EntryAction.delete:
        _showDeleteDialog(context);
        break;
      case EntryAction.share:
-        AndroidAppService.shareEntries(selection).then((success) {
+        final collection = context.read<CollectionLens>();
+        AndroidAppService.shareEntries(collection.selection).then((success) {
          if (!success) showNoMatchingAppDialog(context);
        });
        break;
@ -55,16 +50,25 @@ class EntrySetActionDelegate with FeedbackMixin, PermissionAwareMixin, SizeAware
        _moveSelection(context, moveType: MoveType.move);
        break;
      case CollectionAction.refreshMetadata:
-        source.refreshMetadata(selection);
-        collection.browse();
+        _refreshMetadata(context);
        break;
      default:
        break;
    }
  }

-  Future<void> _moveSelection(BuildContext context, {@required MoveType moveType}) async {
-    final selectionDirs = selection.where((e) => e.path != null).map((e) => e.directory).toSet();
+  void _refreshMetadata(BuildContext context) {
+    final collection = context.read<CollectionLens>();
+    collection.source.refreshMetadata(collection.selection);
+    collection.browse();
+  }
+
+  Future<void> _moveSelection(BuildContext context, {required MoveType moveType}) async {
+    final collection = context.read<CollectionLens>();
+    final source = collection.source;
+    final selection = collection.selection;
+
+    final selectionDirs = selection.where((e) => e.path != null).map((e) => e.directory).cast<String>().toSet();
    if (moveType == MoveType.move) {
      // check whether moving is possible given OS restrictions,
      // before asking to pick a destination album
@ -82,7 +86,7 @@ class EntrySetActionDelegate with FeedbackMixin, PermissionAwareMixin, SizeAware
    final destinationAlbum = await Navigator.push(
      context,
      MaterialPageRoute<String>(
-        settings: RouteSettings(name: AlbumPickPage.routeName),
+        settings: const RouteSettings(name: AlbumPickPage.routeName),
        builder: (context) => AlbumPickPage(source: source, moveType: moveType),
      ),
    );
@ -99,6 +103,8 @@ class EntrySetActionDelegate with FeedbackMixin, PermissionAwareMixin, SizeAware

    final copy = moveType == MoveType.copy;
    final todoCount = todoEntries.length;
+    assert(todoCount > 0);
+
    source.pauseMonitoring();
    showOpReport<MoveOpEvent>(
      context: context,
@ -115,6 +121,11 @@ class EntrySetActionDelegate with FeedbackMixin, PermissionAwareMixin, SizeAware
        collection.browse();
        source.resumeMonitoring();

+        // cleanup
+        if (moveType == MoveType.move) {
+          await storageService.deleteEmptyDirectories(selectionDirs);
+        }
+
        final l10n = context.l10n;
        final movedCount = movedOps.length;
        if (movedCount < todoCount) {
@ -122,19 +133,56 @@ class EntrySetActionDelegate with FeedbackMixin, PermissionAwareMixin, SizeAware
          showFeedback(context, copy ? l10n.collectionCopyFailureFeedback(count) : l10n.collectionMoveFailureFeedback(count));
        } else {
          final count = movedCount;
-          showFeedback(context, copy ? l10n.collectionCopySuccessFeedback(count) : l10n.collectionMoveSuccessFeedback(count));
-        }
-
-        // cleanup
-        if (moveType == MoveType.move) {
-          await storageService.deleteEmptyDirectories(selectionDirs);
+          showFeedback(
+            context,
+            copy ? l10n.collectionCopySuccessFeedback(count) : l10n.collectionMoveSuccessFeedback(count),
+            SnackBarAction(
+              label: context.l10n.showButtonLabel,
+              onPressed: () async {
+                final highlightInfo = context.read<HighlightInfo>();
+                var targetCollection = collection;
+                if (collection.filters.any((f) => f is AlbumFilter)) {
+                  final filter = AlbumFilter(destinationAlbum, source.getAlbumDisplayName(context, destinationAlbum));
+                  // we could simply add the filter to the current collection
+                  // but navigating makes the change less jarring
+                  targetCollection = CollectionLens(
+                    source: collection.source,
+                    filters: collection.filters,
+                    groupFactor: collection.groupFactor,
+                    sortFactor: collection.sortFactor,
+                  )..addFilter(filter);
+                  unawaited(Navigator.pushReplacement(
+                    context,
+                    MaterialPageRoute(
+                      settings: const RouteSettings(name: CollectionPage.routeName),
+                      builder: (context) {
+                        return CollectionPage(
+                          targetCollection,
+                        );
+                      },
+                    ),
+                  ));
+                  await Future.delayed(Durations.staggeredAnimationPageTarget);
+                }
+                await Future.delayed(Durations.highlightScrollInitDelay);
+                final newUris = movedOps.map((v) => v.newFields['uri'] as String?).toSet();
+                final targetEntry = targetCollection.sortedEntries.firstWhereOrNull((entry) => newUris.contains(entry.uri));
+                if (targetEntry != null) {
+                  highlightInfo.trackItem(targetEntry, highlightItem: targetEntry);
+                }
+              },
+            ),
+          );
        }
      },
    );
  }

  Future<void> _showDeleteDialog(BuildContext context) async {
-    final selectionDirs = selection.where((e) => e.path != null).map((e) => e.directory).toSet();
+    final collection = context.read<CollectionLens>();
+    final source = collection.source;
+    final selection = collection.selection;
+    final selectionDirs = selection.where((e) => e.path != null).map((e) => e.directory).cast<String>().toSet();
    final todoCount = selection.length;

    final confirmed = await showDialog<bool>(
--- a/lib/widgets/collection/filter_bar.dart
+++ b/lib/widgets/collection/filter_bar.dart
@ -9,18 +9,18 @@ class FilterBar extends StatefulWidget implements PreferredSizeWidget {

  final List<CollectionFilter> filters;
  final bool removable;
-  final FilterCallback onTap;
+  final FilterCallback? onTap;

  FilterBar({
-    Key key,
-    @required Set<CollectionFilter> filters,
-    @required this.removable,
+    Key? key,
+    required Set<CollectionFilter> filters,
+    required this.removable,
    this.onTap,
  })  : filters = List<CollectionFilter>.from(filters)..sort(),
        super(key: key);

  @override
-  final Size preferredSize = Size.fromHeight(preferredHeight);
+  final Size preferredSize = const Size.fromHeight(preferredHeight);

  @override
  _FilterBarState createState() => _FilterBarState();
@ -28,9 +28,9 @@ class FilterBar extends StatefulWidget implements PreferredSizeWidget {

 class _FilterBarState extends State<FilterBar> {
  final GlobalKey<AnimatedListState> _animatedListKey = GlobalKey(debugLabel: 'filter-bar-animated-list');
-  CollectionFilter _userTappedFilter;
+  CollectionFilter? _userTappedFilter;

-  FilterCallback get onTap => widget.onTap;
+  FilterCallback? get onTap => widget.onTap;

  @override
  void didUpdateWidget(covariant FilterBar oldWidget) {
@ -46,7 +46,7 @@ class _FilterBarState extends State<FilterBar> {
      // only animate item removal when triggered by a user interaction with the chip,
      // not from automatic chip replacement following chip selection
      final animate = _userTappedFilter == filter;
-      listState.removeItem(
+      listState!.removeItem(
        index,
        animate
            ? (context, animation) {
@ -69,7 +69,7 @@ class _FilterBarState extends State<FilterBar> {
    });
    added.forEach((filter) {
      final index = current.indexOf(filter);
-      listState.insertItem(
+      listState!.insertItem(
        index,
        duration: Duration.zero,
      );
@ -92,10 +92,10 @@ class _FilterBarState extends State<FilterBar> {
          key: _animatedListKey,
          initialItemCount: widget.filters.length,
          scrollDirection: Axis.horizontal,
-          physics: BouncingScrollPhysics(),
-          padding: EdgeInsets.only(left: 8),
+          physics: const BouncingScrollPhysics(),
+          padding: const EdgeInsets.only(left: 8),
          itemBuilder: (context, index, animation) {
-            if (index >= widget.filters.length) return null;
+            if (index >= widget.filters.length) return const SizedBox();
            return _buildChip(widget.filters.toList()[index]);
          },
        ),
@ -105,7 +105,7 @@ class _FilterBarState extends State<FilterBar> {

  Padding _buildChip(CollectionFilter filter) {
    return Padding(
-      padding: EdgeInsets.only(right: 8),
+      padding: const EdgeInsets.only(right: 8),
      child: Center(
        child: AvesFilterChip(
          key: ValueKey(filter),
@ -115,7 +115,7 @@ class _FilterBarState extends State<FilterBar> {
          onTap: onTap != null
              ? (filter) {
                  _userTappedFilter = filter;
-                  onTap(filter);
+                  onTap!(filter);
                }
              : null,
        ),
--- a/lib/widgets/collection/grid/headers/album.dart
+++ b/lib/widgets/collection/grid/headers/album.dart
@ -2,37 +2,43 @@ import 'package:aves/model/source/collection_source.dart';
 import 'package:aves/model/source/section_keys.dart';
 import 'package:aves/theme/icons.dart';
 import 'package:aves/utils/android_file_utils.dart';
+import 'package:aves/widgets/common/extensions/build_context.dart';
 import 'package:aves/widgets/common/grid/header.dart';
 import 'package:aves/widgets/common/identity/aves_icons.dart';
 import 'package:flutter/material.dart';

 class AlbumSectionHeader extends StatelessWidget {
-  final String directory, albumName;
+  final String? directory, albumName;

  const AlbumSectionHeader({
-    Key key,
-    @required this.directory,
-    @required this.albumName,
+    Key? key,
+    required this.directory,
+    required this.albumName,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
-    var albumIcon = IconUtils.getAlbumIcon(context: context, album: directory);
-    if (albumIcon != null) {
-      albumIcon = Material(
-        type: MaterialType.circle,
-        elevation: 3,
-        color: Colors.transparent,
-        shadowColor: Colors.black,
-        child: albumIcon,
-      );
+    Widget? albumIcon;
+    if (directory != null) {
+      albumIcon = IconUtils.getAlbumIcon(context: context, albumPath: directory!);
+      if (albumIcon != null) {
+        albumIcon = RepaintBoundary(
+          child: Material(
+            type: MaterialType.circle,
+            elevation: 3,
+            color: Colors.transparent,
+            shadowColor: Colors.black,
+            child: albumIcon,
+          ),
+        );
+      }
    }
    return SectionHeader(
      sectionKey: EntryAlbumSectionKey(directory),
      leading: albumIcon,
-      title: albumName,
-      trailing: androidFileUtils.isOnRemovableStorage(directory)
-          ? Icon(
+      title: albumName ?? context.l10n.sectionUnknown,
+      trailing: directory != null && androidFileUtils.isOnRemovableStorage(directory!)
+          ? const Icon(
              AIcons.removableStorage,
              size: 16,
              color: Color(0xFF757575),
@ -42,7 +48,7 @@ class AlbumSectionHeader extends StatelessWidget {
  }

  static double getPreferredHeight(BuildContext context, double maxWidth, CollectionSource source, EntryAlbumSectionKey sectionKey) {
-    final directory = sectionKey.directory;
+    final directory = sectionKey.directory ?? context.l10n.sectionUnknown;
    return SectionHeader.getPreferredHeight(
      context: context,
      maxWidth: maxWidth,
--- a/lib/widgets/collection/grid/headers/any.dart
+++ b/lib/widgets/collection/grid/headers/any.dart
@ -15,10 +15,10 @@ class CollectionSectionHeader extends StatelessWidget {
  final double height;

  const CollectionSectionHeader({
-    Key key,
-    @required this.collection,
-    @required this.sectionKey,
-    @required this.height,
+    Key? key,
+    required this.collection,
+    required this.sectionKey,
+    required this.height,
  }) : super(key: key);

  @override
@ -29,10 +29,10 @@ class CollectionSectionHeader extends StatelessWidget {
            height: height,
            child: header,
          )
-        : SizedBox.shrink();
+        : const SizedBox.shrink();
  }

-  Widget _buildHeader(BuildContext context) {
+  Widget? _buildHeader(BuildContext context) {
    switch (collection.sortFactor) {
      case EntrySortFactor.date:
        switch (collection.groupFactor) {
@ -60,7 +60,7 @@ class CollectionSectionHeader extends StatelessWidget {
    return AlbumSectionHeader(
      key: ValueKey(sectionKey),
      directory: directory,
-      albumName: source.getAlbumDisplayName(context, directory),
+      albumName: directory != null ? source.getAlbumDisplayName(context, directory) : null,
    );
  }

--- a/lib/widgets/collection/grid/headers/date.dart
+++ b/lib/widgets/collection/grid/headers/date.dart
@ -6,11 +6,11 @@ import 'package:flutter/material.dart';
 import 'package:intl/intl.dart';

 class DaySectionHeader extends StatelessWidget {
-  final DateTime date;
+  final DateTime? date;

  const DaySectionHeader({
-    Key key,
-    @required this.date,
+    Key? key,
+    required this.date,
  }) : super(key: key);

  // Examples (en_US):
@ -33,7 +33,7 @@ class DaySectionHeader extends StatelessWidget {
  // `MEd`:         `1. 26. (화)`
  // `yMEd`:        `2021. 1. 26. (화)`

-  static String _formatDate(BuildContext context, DateTime date) {
+  static String _formatDate(BuildContext context, DateTime? date) {
    final l10n = context.l10n;
    if (date == null) return l10n.sectionUnknown;
    if (date.isToday) return l10n.dateToday;
@ -53,14 +53,14 @@ class DaySectionHeader extends StatelessWidget {
 }

 class MonthSectionHeader extends StatelessWidget {
-  final DateTime date;
+  final DateTime? date;

  const MonthSectionHeader({
-    Key key,
-    @required this.date,
+    Key? key,
+    required this.date,
  }) : super(key: key);

-  static String _formatDate(BuildContext context, DateTime date) {
+  static String _formatDate(BuildContext context, DateTime? date) {
    final l10n = context.l10n;
    if (date == null) return l10n.sectionUnknown;
    if (date.isThisMonth) return l10n.dateThisMonth;
--- a/lib/widgets/collection/grid/section_layout.dart
+++ b/lib/widgets/collection/grid/section_layout.dart
@ -3,23 +3,24 @@ import 'package:aves/model/source/collection_lens.dart';
 import 'package:aves/model/source/section_keys.dart';
 import 'package:aves/widgets/collection/grid/headers/any.dart';
 import 'package:aves/widgets/common/grid/section_layout.dart';
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';

 class SectionedEntryListLayoutProvider extends SectionedListLayoutProvider<AvesEntry> {
  final CollectionLens collection;

  const SectionedEntryListLayoutProvider({
-    @required this.collection,
-    @required double scrollableWidth,
-    @required int columnCount,
-    @required double tileExtent,
-    @required Widget Function(AvesEntry entry) tileBuilder,
-    @required Duration tileAnimationDelay,
-    @required Widget child,
+    required this.collection,
+    required double scrollableWidth,
+    required int columnCount,
+    required double spacing,
+    required double tileExtent,
+    required Widget Function(AvesEntry entry) tileBuilder,
+    required Duration tileAnimationDelay,
+    required Widget child,
  }) : super(
          scrollableWidth: scrollableWidth,
          columnCount: columnCount,
+          spacing: spacing,
          tileExtent: tileExtent,
          tileBuilder: tileBuilder,
          tileAnimationDelay: tileAnimationDelay,
--- a/lib/widgets/collection/grid/selector.dart
+++ b/lib/widgets/collection/grid/selector.dart
@ -19,10 +19,10 @@ class GridSelectionGestureDetector extends StatefulWidget {

  const GridSelectionGestureDetector({
    this.selectable = true,
-    @required this.collection,
-    @required this.scrollController,
-    @required this.appBarHeightNotifier,
-    @required this.child,
+    required this.collection,
+    required this.scrollController,
+    required this.appBarHeightNotifier,
+    required this.child,
  });

  @override
@ -30,16 +30,16 @@ class GridSelectionGestureDetector extends StatefulWidget {
 }

 class _GridSelectionGestureDetectorState extends State<GridSelectionGestureDetector> {
-  bool _pressing = false, _selecting;
-  int _fromIndex, _lastToIndex;
-  Offset _localPosition;
-  EdgeInsets _scrollableInsets;
-  double _scrollSpeedFactor;
-  Timer _updateTimer;
+  bool _pressing = false, _selecting = false;
+  late int _fromIndex, _lastToIndex;
+  late Offset _localPosition;
+  late EdgeInsets _scrollableInsets;
+  late double _scrollSpeedFactor;
+  Timer? _updateTimer;

  CollectionLens get collection => widget.collection;

-  List<AvesEntry> get entries => collection.sortedEntries;
+  List<AvesEntry > get entries => collection.sortedEntries;

  ScrollController get scrollController => widget.scrollController;

@ -102,7 +102,9 @@ class _GridSelectionGestureDetectorState extends State<GridSelectionGestureDetec
    }

    final toEntry = _getEntryAt(_localPosition);
-    _toggleSelectionToIndex(entries.indexOf(toEntry));
+    if (toEntry != null) {
+      _toggleSelectionToIndex(entries.indexOf(toEntry));
+    }
  }

  void _setScrollSpeed(double speedFactor) {
@ -131,7 +133,7 @@ class _GridSelectionGestureDetectorState extends State<GridSelectionGestureDetec
    }
  }

-  AvesEntry _getEntryAt(Offset localPosition) {
+  AvesEntry? _getEntryAt(Offset localPosition) {
    // as of Flutter v1.22.5, `hitTest` on the `ScrollView` render object works fine when it is static,
    // but when it is scrolling (through controller animation), result is incomplete and children are missing,
    // so we use custom layout computation instead to find the entry.
--- a/Show more
+++ b/Show more