fix(player): clear stale tracks before opening media

close #1028

lib/mpv/player/platform/player_android.dart

@@ -99,6 +99,7 @@ class PlayerAndroid extends PlayerBase {
     if (disposed) return;
     await _ensureInitialized();
     final startPosition = media.start ?? Duration.zero;
+    clearTracks();
     resetPlaybackProgress(startPosition);
     setSeekable(false);
 

lib/mpv/player/player_native.dart

@@ -105,6 +105,7 @@ class PlayerNative extends PlayerBase {
     if (disposed) return;
     await _ensureInitialized();
     final startPosition = media.start ?? Duration.zero;
+    clearTracks();
     resetPlaybackProgress(startPosition);
     setSeekable(false);
 

test/mpv/player_open_test.dart

@@ -0,0 +1,100 @@
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/mpv/mpv.dart';
+import 'package:plezy/mpv/player/platform/player_android.dart';
+import 'package:plezy/mpv/player/player_native.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  group('player open', () {
+    test('ExoPlayer clears stale Dart track state before opening new media', () async {
+      await _withMockChannels(
+        methodChannelName: 'com.plezy/exo_player',
+        eventChannelName: 'com.plezy/exo_player/events',
+        testBody: () async {
+          final player = PlayerAndroid();
+          try {
+            _seedTracks(player);
+            expect(player.state.tracks.audio, isNotEmpty);
+            expect(player.state.track.audio, isNotNull);
+
+            await player.open(Media('https://example.test/next.mkv'));
+
+            expect(player.state.tracks.audio, isEmpty);
+            expect(player.state.tracks.subtitle, isEmpty);
+            expect(player.state.track.audio, isNull);
+            expect(player.state.track.subtitle, isNull);
+          } finally {
+            await player.dispose();
+          }
+        },
+      );
+    });
+
+    test('MPV clears stale Dart track state before opening new media', () async {
+      await _withMockChannels(
+        methodChannelName: 'com.plezy/mpv_player',
+        eventChannelName: 'com.plezy/mpv_player/events',
+        testBody: () async {
+          final player = PlayerNative();
+          try {
+            _seedTracks(player);
+            expect(player.state.tracks.audio, isNotEmpty);
+            expect(player.state.track.audio, isNotNull);
+
+            await player.open(Media('https://example.test/next.mkv'));
+
+            expect(player.state.tracks.audio, isEmpty);
+            expect(player.state.tracks.subtitle, isEmpty);
+            expect(player.state.track.audio, isNull);
+            expect(player.state.track.subtitle, isNull);
+          } finally {
+            await player.dispose();
+          }
+        },
+      );
+    });
+  });
+}
+
+Future<void> _withMockChannels({
+  required String methodChannelName,
+  required String eventChannelName,
+  required Future<void> Function() testBody,
+}) async {
+  final messenger = TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger;
+  final methodChannel = MethodChannel(methodChannelName);
+  final eventChannel = MethodChannel(eventChannelName);
+
+  messenger.setMockMethodCallHandler(methodChannel, (call) async {
+    switch (call.method) {
+      case 'initialize':
+        return true;
+      case 'observeProperty':
+      case 'setVisible':
+      case 'setProperty':
+      case 'command':
+      case 'open':
+      case 'dispose':
+        return null;
+      default:
+        return null;
+    }
+  });
+  messenger.setMockMethodCallHandler(eventChannel, (call) async => null);
+
+  try {
+    await testBody();
+  } finally {
+    messenger.setMockMethodCallHandler(methodChannel, null);
+    messenger.setMockMethodCallHandler(eventChannel, null);
+  }
+}
+
+void _seedTracks(dynamic player) {
+  player.handlePropertyChange('track-list', const [
+    {'type': 'audio', 'id': '2_0', 'title': 'English', 'lang': 'eng', 'selected': true},
+    {'type': 'sub', 'id': '3_0', 'title': 'English', 'lang': 'eng', 'selected': true},
+  ]);
+}