update.

Author: duan

example/lib/widgets/sound_waveform.dart

@@ -1,8 +1,5 @@
-import 'package:collection/collection.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_webrtc/flutter_webrtc.dart';
 import 'package:livekit_client/livekit_client.dart';
-import 'package:livekit_example/theme.dart';
 
 class SoundWaveformWidget extends StatefulWidget {
   final int count;
@@ -27,25 +24,23 @@ class SoundWaveformWidget extends StatefulWidget {
 class _SoundWaveformWidgetState extends State<SoundWaveformWidget>
     with TickerProviderStateMixin {
   late AnimationController controller;
-  List<double> samples = [0,0,0,0,0,0,0];
- EventsListener<TrackEvent>? _listener;
+  List<double> samples = [0, 0, 0, 0, 0, 0, 0];
+  EventsListener<TrackEvent>? _listener;
 
   void _startVisualizer(AudioTrack track) async {
-    await widget.audioTrack.startVisualizer();
-    _listener?.dispose();
+    await _listener?.dispose();
     _listener = track.createListener();
     _listener?.on<AudioVisualizerEvent>((e) {
-      if(mounted) {
+      if (mounted) {
         setState(() {
-          samples = e.event.map((e) =>  ((e as num) * 100).toDouble()).toList();
+          samples = e.event.map((e) => ((e as num) * 100).toDouble()).toList();
         });
       }
     });
   }
 
   void _stopVisualizer(AudioTrack track) async {
-    await widget.audioTrack.stopVisualizer();
-    _listener?.dispose();
+    await _listener?.dispose();
   }
 
   @override
@@ -105,4 +100,4 @@ class _SoundWaveformWidgetState extends State<SoundWaveformWidget>
       },
     );
   }
-}
+}

lib/src/track/local/local.dart

@@ -60,19 +60,26 @@ mixin VideoTrack on Track {
 
 /// Used to group [LocalAudioTrack] and [RemoteAudioTrack].
 mixin AudioTrack on Track {
-
-  EventChannel? _eventChannel ;
+  EventChannel? _eventChannel;
   StreamSubscription? _streamSubscription;
 
+  @override
+  Future<void> onStarted() => startVisualizer();
+
+  @override
+  Future<void> onStopped() => stopVisualizer();
+
   Future<void> startVisualizer() async {
-    if(_eventChannel != null) {
+    if (_eventChannel != null) {
       return;
     }
 
     await Native.startVisualizer(mediaStreamTrack.id!);
 
-    _eventChannel = EventChannel('io.livekit.audio.visualizer/eventChannel-${mediaStreamTrack.id}');
-    _streamSubscription = _eventChannel?.receiveBroadcastStream().listen((event) {
+    _eventChannel = EventChannel(
+        'io.livekit.audio.visualizer/eventChannel-${mediaStreamTrack.id}');
+    _streamSubscription =
+        _eventChannel?.receiveBroadcastStream().listen((event) {
       //logger.fine('[$objectId] visualizer event(${event})');
       events.emit(AudioVisualizerEvent(
         track: this,
@@ -82,7 +89,7 @@ mixin AudioTrack on Track {
   }
 
   Future<void> stopVisualizer() async {
-    if(_eventChannel == null) {
+    if (_eventChannel == null) {
       return;
     }
     await Native.stopVisualizer(mediaStreamTrack.id!);

lib/src/track/track.dart

@@ -107,9 +107,11 @@ abstract class Track extends DisposableChangeNotifier
     }
 
     logger.fine('$objectId.start()');
-  
+
     startMonitor();
 
+    await onStarted();
+
     _active = true;
     return true;
   }
@@ -125,6 +127,8 @@ abstract class Track extends DisposableChangeNotifier
 
     stopMonitor();
 
+    await onStopped();
+
     logger.fine('$objectId.stop()');
 
     _active = false;
@@ -161,6 +165,12 @@ abstract class Track extends DisposableChangeNotifier
   @internal
   Future<bool> monitorStats();
 
+  @internal
+  Future<void> onStarted() async {}
+
+  @internal
+  Future<void> onStopped() async {}
+
   @internal
   void startMonitor() {
     _monitorTimer ??= Timer.periodic(