Add disposePlayer to platform interface. Retain player.position after dispose.

just_audio_platform_interface/lib/just_audio_platform_interface.dart

@@ -41,6 +41,11 @@ abstract class JustAudioPlatform extends PlatformInterface {
   Future<AudioPlayerPlatform> init(InitRequest request) {
     throw UnimplementedError('init() has not been implemented.');
   }
+
+  /// Disposes of a platform player.
+  Future<DisposePlayerResponse> disposePlayer(DisposePlayerRequest request) {
+    throw UnimplementedError('disposePlayer() has not been implemented.');
+  }
 }
 
 /// A nested platform interface for communicating with a particular player
@@ -53,6 +58,10 @@ abstract class JustAudioPlatform extends PlatformInterface {
 /// `implements` this interface will be broken by newly added
 /// [AudioPlayerPlatform] methods.
 abstract class AudioPlayerPlatform {
+  final String id;
+
+  AudioPlayerPlatform(this.id);
+
   Stream<PlaybackEventMessage> get playbackEventMessageStream {
     throw UnimplementedError(
         'playbackEventMessageStream has not been implemented.');
@@ -103,6 +112,9 @@ abstract class AudioPlayerPlatform {
         "setAndroidAudioAttributes() has not been implemented.");
   }
 
+  /// This method has been superceded by [JustAudioPlatform.disposePlayer].
+  /// For backward compatibility, this method will still be called as a
+  /// fallback if [JustAudioPlatform.disposePlayer] is not implemented.
   Future<DisposeResponse> dispose(DisposeRequest request) {
     throw UnimplementedError("dispose() has not been implemented.");
   }
@@ -244,6 +256,21 @@ class InitRequest {
       };
 }
 
+class DisposePlayerRequest {
+  final String id;
+
+  DisposePlayerRequest({@required this.id});
+
+  Map<dynamic, dynamic> toMap() => {
+        'id': id,
+      };
+}
+
+class DisposePlayerResponse {
+  static DisposePlayerResponse fromMap(Map<dynamic, dynamic> map) =>
+      DisposePlayerResponse();
+}
+
 class LoadRequest {
   final AudioSourceMessage audioSourceMessage;
 

just_audio_platform_interface/lib/method_channel_just_audio.dart

@@ -13,15 +13,22 @@ class MethodChannelJustAudio extends JustAudioPlatform {
     await _mainChannel.invokeMethod('init', request.toMap());
     return MethodChannelAudioPlayer(request.id);
   }
+
+  @override
+  Future<DisposePlayerResponse> disposePlayer(
+      DisposePlayerRequest request) async {
+    return DisposePlayerResponse.fromMap(
+        await _mainChannel.invokeMethod('disposePlayer', request.toMap()));
+  }
 }
 
 /// An implementation of [AudioPlayerPlatform] that uses method channels.
 class MethodChannelAudioPlayer extends AudioPlayerPlatform {
-  final String id;
   final MethodChannel _channel;
 
-  MethodChannelAudioPlayer(this.id)
-      : _channel = MethodChannel('com.ryanheise.just_audio.methods.$id');
+  MethodChannelAudioPlayer(String id)
+      : _channel = MethodChannel('com.ryanheise.just_audio.methods.$id'),
+        super(id);
 
   @override
   Stream<PlaybackEventMessage> get playbackEventMessageStream =>