poc: hero between thumbnail & full screen

android/app/src/main/java/deckers/thibault/aves/MainActivity.java

@@ -77,10 +77,10 @@ public class MainActivity extends FlutterActivity {
         new MethodChannel(getFlutterView(), CHANNEL).setMethodCallHandler(
                 (call, result) -> {
                     switch (call.method) {
-                        case "getImages":
+                        case "getImageEntries":
                             getPermissionResult(result, this);
                             break;
-                        case "getThumbnail": {
+                        case "getImageBytes": {
                             Map map = call.argument("entry");
                             Integer width = call.argument("width");
                             Integer height = call.argument("height");
@@ -88,7 +88,7 @@ public class MainActivity extends FlutterActivity {
                             thumbnailFetcher.fetch(entry, width, height, result);
                             break;
                         }
-                        case "cancelGetThumbnail": {
+                        case "cancelGetImageBytes": {
                             String uri = call.argument("uri");
                             thumbnailFetcher.cancel(uri);
                             result.success(null);
@@ -198,7 +198,7 @@ class BitmapWorkerTask extends AsyncTask<BitmapWorkerTask.MyTaskParams, Void, Bi
         ImageEntry entry = p.entry;
         byte[] data = null;
         if (!this.isCancelled()) {
-            Log.d(LOG_TAG, "getThumbnail with uri=" + entry.getUri() + "(called)");
+            Log.d(LOG_TAG, "getImageBytes with uri=" + entry.getUri() + "(called)");
             // add signature to ignore cache for images which got modified but kept the same URI
             Key signature = new ObjectKey("" + entry.getDateModifiedSecs() + entry.getWidth() + entry.getOrientationDegrees());
             FutureTarget<Bitmap> target = Glide.with(activity)
@@ -218,7 +218,7 @@ class BitmapWorkerTask extends AsyncTask<BitmapWorkerTask.MyTaskParams, Void, Bi
             }
             Glide.with(activity).clear(target);
         } else {
-            Log.d(LOG_TAG, "getThumbnail with uri=" + entry.getUri() + "(cancelled)");
+            Log.d(LOG_TAG, "getImageBytes with uri=" + entry.getUri() + "(cancelled)");
         }
         return new MyTaskResult(p, data);
     }
@@ -230,7 +230,7 @@ class BitmapWorkerTask extends AsyncTask<BitmapWorkerTask.MyTaskParams, Void, Bi
         if (result.data != null) {
             r.success(result.data);
         } else {
-            r.error("getthumbnail-null", "failed to get thumbnail for uri=" + result.params.entry.getUri(), null);
+            r.error("getImageBytes-null", "failed to get thumbnail for uri=" + result.params.entry.getUri(), null);
         }
     }
 }

lib/image_fullscreen_page.dart

@@ -1,17 +1,58 @@
-import 'package:aves/thumbnail.dart';
+import 'dart:typed_data';
+
+import 'package:aves/main.dart';
 import 'package:flutter/material.dart';
 
-class ImageFullscreenPage extends StatelessWidget {
+class ImageFullscreenPage extends StatefulWidget {
   final Map entry;
+  final Uint8List thumbnail;
 
-  ImageFullscreenPage({this.entry});
+  ImageFullscreenPage({this.entry, this.thumbnail});
+
+  @override
+  ImageFullscreenPageState createState() => ImageFullscreenPageState();
+}
+
+class ImageFullscreenPageState extends State<ImageFullscreenPage> {
+  Future<Uint8List> loader;
+
+  int get imageWidth => widget.entry['width'];
+
+  int get imageHeight => widget.entry['width'];
+
+  String get uri => widget.entry['uri'];
+
+  @override
+  void initState() {
+    super.initState();
+    loader = ImageFetcher.getImageBytes(widget.entry, imageWidth, imageHeight);
+  }
+
+  @override
+  void dispose() {
+    ImageFetcher.cancelGetImageBytes(uri);
+    super.dispose();
+  }
 
   @override
   Widget build(BuildContext context) {
-    var width = MediaQuery.of(context).size.width;
+    return FutureBuilder(
-    return Thumbnail(
+        future: loader,
-      entry: entry,
+        builder: (futureContext, AsyncSnapshot<Uint8List> snapshot) {
-      extent: width,
+          var ready = snapshot.connectionState == ConnectionState.done && !snapshot.hasError;
+          Uint8List bytes = ready ? snapshot.data : widget.thumbnail;
+          return Hero(
+            tag: uri,
+            child: Center(
+              child: Image.memory(
+                bytes,
+                width: imageWidth.toDouble(),
+                height: imageHeight.toDouble(),
+                fit: BoxFit.contain,
+                gaplessPlayback: true,
+              ),
+            ),
           );
+        });
   }
 }

lib/main.dart

@@ -1,8 +1,8 @@
 import 'dart:typed_data';
-import 'package:aves/image_fullscreen_page.dart';
+
+import 'package:aves/settings.dart';
 import 'package:aves/thumbnail.dart';
 import 'package:draggable_scrollbar/draggable_scrollbar.dart';
-
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
@@ -25,11 +25,9 @@ class MyApp extends StatelessWidget {
 class ImageFetcher {
   static const platform = const MethodChannel('deckers.thibault.aves/mediastore');
 
-  static double devicePixelRatio;
+  static Future<List> getImageEntries() async {
-
-  static Future<List> getImages() async {
     try {
-      final result = await platform.invokeMethod('getImages');
+      final result = await platform.invokeMethod('getImageEntries');
       return result as List;
     } on PlatformException catch (e) {
       debugPrint('failed with exception=${e.message}');
@@ -37,12 +35,12 @@ class ImageFetcher {
     return [];
   }
 
-  static Future<Uint8List> getThumbnail(Map entry, double width, double height) async {
+  static Future<Uint8List> getImageBytes(Map entry, int width, int height) async {
     try {
-      final result = await platform.invokeMethod('getThumbnail', <String, dynamic>{
+      final result = await platform.invokeMethod('getImageBytes', <String, dynamic>{
         'entry': entry,
-        'width': (width * devicePixelRatio).round(),
+        'width': width,
-        'height': (height * devicePixelRatio).round(),
+        'height': height,
       });
       return result as Uint8List;
     } on PlatformException catch (e) {
@@ -51,9 +49,9 @@ class ImageFetcher {
     return Uint8List(0);
   }
 
-  static cancelGetThumbnail(String uri) async {
+  static cancelGetImageBytes(String uri) async {
     try {
-      await platform.invokeMethod('cancelGetThumbnail', <String, dynamic>{
+      await platform.invokeMethod('cancelGetImageBytes', <String, dynamic>{
         'uri': uri,
       });
     } on PlatformException catch (e) {
@@ -79,11 +77,11 @@ class _MyHomePageState extends State<MyHomePage> {
   void initState() {
     super.initState();
     imageCache.maximumSizeBytes = 100 * 1024 * 1024;
-    imageLoader = ImageFetcher.getImages();
+    imageLoader = ImageFetcher.getImageEntries();
 
     WidgetsBinding.instance.addPostFrameCallback((duration) {
-      ImageFetcher.devicePixelRatio = MediaQuery.of(context).devicePixelRatio;
+      settings.devicePixelRatio = MediaQuery.of(context).devicePixelRatio;
-      debugPrint('$runtimeType devicePixelRatio=${ImageFetcher.devicePixelRatio}');
+      debugPrint('$runtimeType devicePixelRatio=${settings.devicePixelRatio}');
     });
   }
 
@@ -122,24 +120,9 @@ class _MyHomePageState extends State<MyHomePage> {
                         maxCrossAxisExtent: extent,
                       ),
                       itemBuilder: (gridContext, index) {
-                        var imageEntryMap = imageEntryList[index] as Map;
+                        return Thumbnail(
-                        return GestureDetector(
+                          entry: imageEntryList[index] as Map,
-                          onTap: () => Navigator.push(
-                                context,
-                                MaterialPageRoute(builder: (context) => ImageFullscreenPage(entry: imageEntryMap)),
-                              ),
-                          child: Container(
-                            decoration: BoxDecoration(
-                              border: Border.all(
-                                color: Colors.grey.shade700,
-                                width: 0.5,
-                              ),
-                            ),
-                            child: Thumbnail(
-                              entry: imageEntryMap,
                           extent: extent,
-                            ),
-                          ),
                         );
                       },
                       itemCount: imageEntryList.length,

lib/settings.dart

@@ -0,0 +1,7 @@
+final Settings settings = Settings._private();
+
+class Settings {
+  double devicePixelRatio;
+
+  Settings._private();
+}

lib/thumbnail.dart

@@ -1,7 +1,10 @@
+import 'dart:math';
 import 'dart:typed_data';
 
+import 'package:aves/image_fullscreen_page.dart';
 import 'package:aves/main.dart';
 import 'package:aves/mime_types.dart';
+import 'package:aves/settings.dart';
 import 'package:flutter/material.dart';
 import 'package:transparent_image/transparent_image.dart';
 
@@ -17,16 +20,20 @@ class Thumbnail extends StatefulWidget {
 
 class ThumbnailState extends State<Thumbnail> {
   Future<Uint8List> loader;
+  Uint8List bytes;
+
+  String get uri => widget.entry['uri'];
 
   @override
   void initState() {
     super.initState();
-    loader = ImageFetcher.getThumbnail(widget.entry, widget.extent, widget.extent);
+    var dim = (widget.extent * settings.devicePixelRatio).round();
+    loader = ImageFetcher.getImageBytes(widget.entry, dim, dim);
   }
 
   @override
   void dispose() {
-    ImageFetcher.cancelGetThumbnail(widget.entry['uri']);
+    ImageFetcher.cancelGetImageBytes(uri);
     super.dispose();
   }
 
@@ -36,22 +43,50 @@ class ThumbnailState extends State<Thumbnail> {
     var isVideo = mimeType.startsWith(MimeTypes.MIME_VIDEO);
     var isGif = mimeType == MimeTypes.MIME_GIF;
     var iconSize = widget.extent / 4;
-    return FutureBuilder(
+    return GestureDetector(
+      onTap: () => Navigator.push(
+        context,
+        MaterialPageRoute(
+          builder: (context) => ImageFullscreenPage(entry: widget.entry, thumbnail: bytes),
+        ),
+      ),
+      child: Container(
+        decoration: BoxDecoration(
+          border: Border.all(
+            color: Colors.grey.shade700,
+            width: 0.5,
+          ),
+        ),
+        child: FutureBuilder(
             future: loader,
             builder: (futureContext, AsyncSnapshot<Uint8List> snapshot) {
-          var ready = snapshot.connectionState == ConnectionState.done && !snapshot.hasError;
+              if (bytes == null && snapshot.connectionState == ConnectionState.done && !snapshot.hasError) {
-          Uint8List bytes = ready ? snapshot.data : kTransparentImage;
+                bytes = snapshot.data;
-          return Hero(
+              }
-            tag: widget.entry['uri'],
+              return Stack(
-            child: Stack(
                 alignment: AlignmentDirectional.bottomStart,
                 children: [
-                Image.memory(
+                  Hero(
-                  bytes,
+                    tag: uri,
-                  width: widget.extent,
+                    child: LayoutBuilder(
-                  height: widget.extent,
+                      builder: (context, constraints) {
+                        // during hero animation back from a fullscreen image,
+                        // the image covers the whole screen (because of the 'fit' prop and the full screen hero constraints)
+                        // so we wrap the image to apply better constraints
+                        var dim = min(constraints.maxWidth, constraints.maxHeight);
+                        return Container(
+                          alignment: Alignment.center,
+                          constraints: BoxConstraints.tight(Size(dim, dim)),
+                          child: Image.memory(
+                            bytes ?? kTransparentImage,
+                            width: dim,
+                            height: dim,
                             fit: BoxFit.cover,
                           ),
+                        );
+                      }
+                    ),
+                  ),
                   if (isVideo)
                     Icon(
                       Icons.play_circle_outline,
@@ -63,8 +98,9 @@ class ThumbnailState extends State<Thumbnail> {
                       size: iconSize,
                     ),
                 ],
+              );
+            }),
       ),
     );
-        });
   }
 }