settings: add option to force-restore state

Add an option to restore the previous playback state.

This allows me to avoid having to use force stop to restore a previous
state.

app/src/main/java/org/oxycblt/auxio/MainActivity.kt

@@ -38,13 +38,14 @@ import org.oxycblt.auxio.util.systemBarInsetsCompat
 /**
  * The single [AppCompatActivity] for Auxio.
  *
- * TODO: Add error screens. This likely has to be an external activity, so it is blocked by
+ * TODO: Add error screens.
- * eliminating exitProcess from the app.
  *
  * TODO: Custom language support
  *
  * TODO: Add multi-select
  *
+ * TODO: Bug test runtime rescanning
+ *
  * @author OxygenCobalt
  */
 class MainActivity : AppCompatActivity() {

app/src/main/java/org/oxycblt/auxio/home/HomeFragment.kt

@@ -315,7 +315,6 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
     }
 
     private fun handleIndexingState(binding: FragmentHomeBinding, indexing: Indexer.Indexing) {
-        updateFab()
         binding.homeIndexingContainer.visibility = View.VISIBLE
         binding.homeIndexingProgress.visibility = View.VISIBLE
         binding.homeIndexingAction.visibility = View.INVISIBLE

app/src/main/java/org/oxycblt/auxio/image/BitmapProvider.kt

@@ -83,6 +83,7 @@ class BitmapProvider(private val context: Context) {
      * Release this instance, canceling all image load jobs. This should be ran when the object is
      * no longer used.
      */
+    @Synchronized
     fun release() {
         currentRequest?.run { disposable.dispose() }
         currentRequest = null

app/src/main/java/org/oxycblt/auxio/music/IndexerService.kt

@@ -119,10 +119,15 @@ class IndexerService : Service(), Indexer.Controller, Settings.Callback {
                             imageLoader.memoryCache?.clear()
 
                             // PlaybackStateManager needs to be updated. We would do this in the
-                            // playback module, but this service could is the only component
+                            // playback module, but this service could be the only component capable
-                            // capable of doing long-running background work as it stands.
+                            // of doing this at a particular point. Note that while it's certain
-                            playbackManager.sanitize(
+                            // that PlaybackStateManager is initialized by now, it's best to be safe
-                                PlaybackStateDatabase.getInstance(this@IndexerService), newLibrary)
+                            // and check first.
+                            if (playbackManager.isInitialized) {
+                                playbackManager.sanitize(
+                                    PlaybackStateDatabase.getInstance(this@IndexerService),
+                                    newLibrary)
+                            }
                         }
 
                         musicStore.updateLibrary(newLibrary)

app/src/main/java/org/oxycblt/auxio/music/Music.kt

@@ -30,6 +30,8 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
 
 /** [Item] variant that represents a music item. */
 sealed class Music : Item() {
+    // TODO: Split ID into an ID derived from all fields and a persistent ID derived from stable fields
+
     /** The raw name of this item. Null if unknown. */
     abstract val rawName: String?
 

app/src/main/java/org/oxycblt/auxio/playback/PlaybackViewModel.kt

@@ -18,7 +18,6 @@
 package org.oxycblt.auxio.playback
 
 import android.app.Application
-import android.content.Context
 import android.net.Uri
 import androidx.lifecycle.AndroidViewModel
 import androidx.lifecycle.viewModelScope
@@ -276,13 +275,22 @@ class PlaybackViewModel(application: Application) :
     // --- SAVE/RESTORE FUNCTIONS ---
 
     /** Force save the current [PlaybackStateManager] state to the database. */
-    fun savePlaybackState(context: Context, onDone: () -> Unit) {
+    fun savePlaybackState(onDone: () -> Unit) {
         viewModelScope.launch {
-            playbackManager.saveState(PlaybackStateDatabase.getInstance(context))
+            playbackManager.saveState(PlaybackStateDatabase.getInstance(application))
             onDone()
         }
     }
 
+    /** Force restore the last [PlaybackStateManager] saved state */
+    fun restorePlaybackState(onDone: (Boolean) -> Unit) {
+        viewModelScope.launch {
+            val restored =
+                playbackManager.restoreState(PlaybackStateDatabase.getInstance(application))
+            onDone(restored)
+        }
+    }
+
     /** An action delayed until the complete load of the music library. */
     sealed class DelayedAction {
         object RestoreState : DelayedAction()

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateDatabase.kt

@@ -38,7 +38,7 @@ import org.oxycblt.auxio.util.requireBackgroundThread
  * But that would needlessly bloat my app and has crippling bugs.
  * @author OxygenCobalt
  */
-class PlaybackStateDatabase(context: Context) :
+class PlaybackStateDatabase private constructor(context: Context) :
     SQLiteOpenHelper(context, DB_NAME, null, DB_VERSION) {
 
     override fun onCreate(db: SQLiteDatabase) {

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateManager.kt

@@ -30,6 +30,7 @@ import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.settings.Settings
 import org.oxycblt.auxio.util.logD
 import org.oxycblt.auxio.util.logW
+import org.oxycblt.auxio.util.unlikelyToBeNull
 
 /**
  * Master class (and possible god object) for the playback state.
@@ -357,17 +358,20 @@ class PlaybackStateManager private constructor() {
 
     // --- PERSISTENCE FUNCTIONS ---
 
-    /** Restore the state from the [database] */
+    /** Restore the state from the [database]. Returns if a state was restored. */
-    suspend fun restoreState(database: PlaybackStateDatabase) {
+    suspend fun restoreState(database: PlaybackStateDatabase): Boolean {
-        val library = musicStore.library ?: return
+        val library = musicStore.library ?: return false
         val state = withContext(Dispatchers.IO) { database.read(library) }
 
         synchronized(this) {
-            if (state != null) {
+            val exists = state != null
-                applyStateImpl(state)
+            if (exists) {
+                applyStateImpl(unlikelyToBeNull(state))
             }
 
             isInitialized = true
+
+            return exists
         }
     }
 
@@ -383,6 +387,8 @@ class PlaybackStateManager private constructor() {
     suspend fun sanitize(database: PlaybackStateDatabase, newLibrary: MusicStore.Library) {
         // Since we need to sanitize the state and re-save it for consistency, take the
         // easy way out and just write a new state and restore from it. Don't really care.
+        // FIXME: This hack actually creates bugs if a user were to save the state at just
+        //  the right time, replace it with something that operates at runtime
         logD("Sanitizing state")
         val state = synchronized(this) { makeStateImpl() }
 
@@ -394,7 +400,7 @@ class PlaybackStateManager private constructor() {
 
         synchronized(this) {
             if (sanitizedState != null) {
-                applyStateImpl(state)
+                applyStateImpl(sanitizedState)
             }
         }
     }

app/src/main/java/org/oxycblt/auxio/settings/SettingsListFragment.kt

@@ -50,9 +50,9 @@ import org.oxycblt.auxio.util.systemBarInsetsCompat
  * The actual fragment containing the settings menu. Inherits [PreferenceFragmentCompat].
  * @author OxygenCobalt
  *
- * TODO: Add option to restore the previous state
- *
  * TODO: Add option to not restore state
+ *
+ * TODO: Disable playback state options when music is loading
  */
 @Suppress("UNUSED")
 class SettingsListFragment : PreferenceFragmentCompat() {
@@ -120,10 +120,16 @@ class SettingsListFragment : PreferenceFragmentCompat() {
     override fun onPreferenceTreeClick(preference: Preference): Boolean {
         when (preference.key) {
             getString(R.string.set_key_save_state) -> {
-                playbackModel.savePlaybackState(requireContext()) {
+                playbackModel.savePlaybackState { context?.showToast(R.string.lbl_state_saved) }
-                    context?.showToast(R.string.lbl_state_saved)
-                }
             }
+            getString(R.string.set_key_restore_state) ->
+                playbackModel.restorePlaybackState { restored ->
+                    if (restored) {
+                        context?.showToast(R.string.lbl_state_restored)
+                    } else {
+                        context?.showToast(R.string.err_did_not_restore)
+                    }
+                }
             getString(R.string.set_key_reindex) -> {
                 indexerModel.reindex()
             }

app/src/main/java/org/oxycblt/auxio/ui/M3Toolbar.kt

@@ -25,7 +25,10 @@ import com.google.android.material.appbar.MaterialToolbar
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.util.getDimenSizeSafe
 
-/** [MaterialToolbar] that automatically fixes padding in order to align with the M3 specs. */
+/**
+ * [MaterialToolbar] that automatically fixes padding in order to align with the M3 specs.
+ * @author OxygenCobalt
+ */
 class M3Toolbar : MaterialToolbar {
     constructor(context: Context) : super(context)
 

app/src/main/res/layout/fragment_home.xml

@@ -50,6 +50,7 @@
             android:id="@+id/home_indexing_container"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
+            android:visibility="invisible"
             android:layout_margin="@dimen/spacing_medium">
 
             <androidx.constraintlayout.widget.ConstraintLayout

app/src/main/res/values/settings.xml

@@ -24,6 +24,7 @@
     <string name="set_key_repeat_pause" translatable="false">KEY_LOOP_PAUSE</string>
 
     <string name="set_key_save_state" translatable="false">auxio_save_state</string>
+    <string name="set_key_restore_state" translatable="false">auxio_restore_state</string>
     <string name="set_key_reindex" translatable="false">auxio_reindex</string>
     <string name="set_key_music_dirs" translatable="false">auxio_music_dirs</string>
     <string name="set_key_music_dirs_include" translatable="false">auxio_include_dirs</string>

app/src/main/res/values/strings.xml

@@ -53,7 +53,10 @@
     <string name="lbl_bitrate">Bit rate</string>
     <string name="lbl_sample_rate">Sample rate</string>
 
+    <!-- Referring to playback state -->
     <string name="lbl_state_saved">State saved</string>
+    <!-- Referring to playback state -->
+    <string name="lbl_state_restored">State restored</string>
 
     <!-- Limit to 10 characters -->
     <string name="lbl_shuffle_shortcut_short">Shuffle</string>
@@ -131,6 +134,8 @@
     <string name="set_content">Content</string>
     <string name="set_save">Save playback state</string>
     <string name="set_save_desc">Save the current playback state now</string>
+    <string name="set_restore">Restore playback state</string>
+    <string name="set_restore_desc">Restore the previously saved playback state (if any)</string>
     <string name="set_reindex">Reload music</string>
     <string name="set_reindex_desc">May wipe playback state</string>
     <string name="set_dirs">Music folders</string>
@@ -151,6 +156,8 @@
     <string name="err_no_dirs">No Folders</string>
     <string name="err_bad_dir">This folder is not supported</string>
     <string name="err_too_small">Auxio does not support this window size</string>
+    <!-- Referring to playback state -->
+    <string name="err_did_not_restore">No state could be restored</string>
 
     <!-- Hint Namespace | EditText Hints -->
     <string name="hint_search_library">Search your library…</string>
@@ -190,11 +197,17 @@
     <string name="def_widget_artist">Artist Name</string>
 
     <!-- Codec Namespace | Format names -->
+    <!-- "Audio" should be translated -->
     <string name="cdc_mp3">MPEG-1 Audio</string>
+    <!-- "Audio" should be translated -->
     <string name="cdc_mp4">MPEG-4 Audio</string>
+    <!-- "Audio" should be translated -->
     <string name="cdc_ogg">Ogg Audio</string>
+    <!-- "Audio" should be translated -->
     <string name="cdc_mka">Matroska Audio</string>
+    <!-- "Advanced Audio Coding" can optionally be translated -->
     <string name="cdc_aac">Advanced Audio Coding (AAC)</string>
+    <!-- "Free Lossless Audio Codec" can optionally be translated -->
     <string name="cdc_flac">Free Lossless Audio Codec (FLAC)</string>
 
     <!-- Color Label namespace | Accent names -->
@@ -219,9 +232,13 @@
     <!-- Format Namespace | Value formatting/plurals -->
     <string name="fmt_disc_no">Disc %d</string>
 
+    <!-- Use your native country's abbreviation for decibel units. -->
     <string name="fmt_db_pos">+%.1f dB</string>
+    <!-- Use your native country's abbreviation for decibel units. -->
     <string name="fmt_db_neg">-%.1f dB</string>
+    <!-- Use your native country's abbreviation for bitrate units. -->
     <string name="fmt_bitrate">%d kbps</string>
+    <!-- Use your native country's abbreviation for hertz units. -->
     <string name="fmt_sample_rate">%d Hz</string>
 
     <string name="fmt_indexing">Loading your music library… (%1$d/%2$d)</string>

app/src/main/res/xml/prefs_main.xml

@@ -161,6 +161,12 @@
             app:summary="@string/set_save_desc"
             app:title="@string/set_save" />
 
+        <Preference
+            app:iconSpaceReserved="false"
+            app:key="@string/set_key_restore_state"
+            app:summary="@string/set_restore_desc"
+            app:title="@string/set_restore" />
+
         <Preference
             app:iconSpaceReserved="false"
             app:key="@string/set_key_reindex"

info/FAQ.md

@@ -43,6 +43,11 @@ This is expected since reading from the audio database takes awhile, especially
 This is a current limitation with the music loader. To remedy this, go to Settings -> Reload music whenever new songs are added.
 I hope to make the app rescan music on the fly eventually.
 
+#### Why does playback pause whenever music is reloaded?
+Whenever the music library signifigantly changes, updating the player's data while it is still playing may result in
+unwanted bugs or unexpected music playing. To safeguard against this, Auxio will pause whenever it reloads a new
+music library. 
+
 #### There should be one artist, but instead I get a bunch of "Artist & Collaborator" artists!
 This likely means your tags are wrong. By default, Auxio will use the "album artist" tag for
 grouping if present, falling back to the "artist" tag otherwise. If your music does not have