Better handling of sequential platform activations/deactivations.

just_audio/README.md

@@ -32,7 +32,7 @@ Please consider reporting any bugs you encounter [here](https://github.com/ryanh
 `load()` and `stop()` have new behaviours in 0.6.x documented [here](https://pub.dev/documentation/just_audio/latest/just_audio/AudioPlayer-class.html) that provide greater flexibility in how system resources are acquired and released. For a quick migration that maintains 0.5.x behaviour:
 
 * Replace `await player.load(source);` by `await player.setAudioSource(source);`
-* Replace `await stop();` by `await player.pause(); await player.seek(Duration.zero);
+* Replace `await stop();` by `await player.pause(); await player.seek(Duration.zero);`
 
 Also beware that `playbackEventStream` will now emit events strictly when the fields in `PlaybackEvent` change. In 0.5.x this often (by chance) coincided with `playing` state changes. Apps that depended on this behaviour will break in 0.6.x and should explicitly listen for `playing` state changes via `playingStream` or `playerStateStream`.
 

just_audio/lib/just_audio.dart

@@ -542,18 +542,14 @@ class AudioPlayer {
     _playbackEventSubject.add(_playbackEvent = PlaybackEvent(
         currentIndex: initialIndex, updatePosition: initialPosition));
     _broadcastSequence();
-    // TODO: If the active platform existed, we should try to retain it.
-    try {
-      await _setPlatformActive(false);
-    } catch (e) {
-      print("Error deactivating previous platform: $e (ignoring)");
-    }
     _audioSource = source;
     _broadcastSequence();
     Duration duration;
     if (playing) preload = true;
     if (preload) {
       duration = await load();
+    } else {
+      await _setPlatformActive(false);
     }
     return duration;
   }
@@ -573,8 +569,14 @@ class AudioPlayer {
     if (_audioSource == null) {
       throw Exception('Must set AudioSource before loading');
     }
+    if (_active) {
+      return await _load(await _platform, _audioSource,
+          initialSeekValues: _initialSeekValues);
+    } else {
+      // This will implicitly load the current audio source.
       return await _setPlatformActive(true);
     }
+  }
 
   void _broadcastSequence() {
     _sequenceSubject.add(_audioSource?.sequence);
@@ -601,7 +603,7 @@ class AudioPlayer {
   }
 
   Future<Duration> _load(AudioPlayerPlatform platform, AudioSource source,
-      {Duration initialPosition, int initialIndex}) async {
+      {_InitialSeekValues initialSeekValues}) async {
     try {
       if (!kIsWeb && source._requiresHeaders) {
         if (_proxy == null) {
@@ -610,18 +612,21 @@ class AudioPlayer {
         }
       }
       await source._setup(this);
-      source._shuffle(initialIndex: initialIndex ?? 0);
+      source._shuffle(initialIndex: initialSeekValues?.index ?? 0);
       _updateShuffleIndices();
       platform ??= await _platform;
       _durationFuture = platform
           .load(LoadRequest(
             audioSourceMessage: source._toMessage(),
-            initialPosition: initialPosition,
+            initialPosition: initialSeekValues?.position,
-            initialIndex: initialIndex,
+            initialIndex: initialSeekValues?.index,
           ))
           .then((response) => response.duration);
       final duration = await _durationFuture;
       _durationSubject.add(duration);
+      // Wait for loading state to pass.
+      await processingStateStream
+          .firstWhere((state) => state != ProcessingState.loading);
       return duration;
     } on PlatformException catch (e) {
       try {
@@ -653,9 +658,6 @@ class AudioPlayer {
                 start: start,
                 end: end,
               ));
-    // Wait for loading state to pass.
-    await processingStateStream
-        .firstWhere((state) => state != ProcessingState.loading);
     return duration;
   }
 
@@ -917,11 +919,6 @@ class AudioPlayer {
     final position = this.position;
     final currentIndex = this.currentIndex;
     final audioSource = _audioSource;
-    final newPlatform = active
-        ? (_nativePlatform =
-            JustAudioPlatform.instance.init(InitRequest(id: _id)))
-        : Future.value(_idlePlatform);
-    _playbackEventSubscription?.cancel();
     final durationCompleter = Completer<Duration>();
     _platform = Future<AudioPlayerPlatform>(() async {
       if (oldPlatformFuture != null) {
@@ -932,7 +929,11 @@ class AudioPlayer {
       }
       // During initialisation, we must only use this platform reference in case
       // _platform is updated again during initialisation.
-      final platform = await newPlatform;
+      final platform = active
+          ? await (_nativePlatform =
+              JustAudioPlatform.instance.init(InitRequest(id: _id)))
+          : _idlePlatform;
+      _playbackEventSubscription?.cancel();
       _playbackEventSubscription =
           platform.playbackEventMessageStream.listen((message) {
         var duration = message.duration;
@@ -999,20 +1000,9 @@ class AudioPlayer {
       }
       if (audioSource != null) {
         try {
-          Duration initialPosition;
-          int initialIndex;
-          if (_initialSeekValues != null) {
-            initialPosition = _initialSeekValues.position;
-            initialIndex = _initialSeekValues.index;
-          } else {
-            initialPosition = position;
-            initialIndex = currentIndex;
-          }
           final duration = await _load(platform, _audioSource,
-              initialPosition: initialPosition, initialIndex: initialIndex);
+              initialSeekValues: _initialSeekValues ??
-          // Wait for loading state to pass.
+                  _InitialSeekValues(position: position, index: currentIndex));
-          await processingStateStream
-              .firstWhere((state) => state != ProcessingState.loading);
           durationCompleter.complete(duration);
         } catch (e, stackTrace) {
           _audioSource = null;

just_audio_web/lib/just_audio_web.dart

@@ -15,12 +15,12 @@ class JustAudioPlugin extends JustAudioPlatform {
   }
 
   Future<AudioPlayerPlatform> init(InitRequest request) async {
-    final player = Html5AudioPlayer(id: request.id);
     if (players.containsKey(request.id)) {
       throw PlatformException(
           code: "error",
           message: "Platform player ${request.id} already exists");
     }
+    final player = Html5AudioPlayer(id: request.id);
     players[request.id] = player;
     return player;
   }