Visualizer implementation for Android.

just_audio_platform_interface/lib/just_audio_platform_interface.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:typed_data';
 
 import 'package:flutter/foundation.dart';
 import 'package:meta/meta.dart' show required;
@@ -68,6 +69,17 @@ abstract class AudioPlayerPlatform {
         'playbackEventMessageStream has not been implemented.');
   }
 
+  /// A stream of visualizer waveform data.
+  Stream<Uint8List> get visualizerWaveformStream {
+    throw UnimplementedError(
+        'visualizerWaveformStream has not been implemented.');
+  }
+
+  /// A stream of visualizer fft data.
+  Stream<Uint8List> get visualizerFftStream {
+    throw UnimplementedError('visualizerFftStream has not been implemented.');
+  }
+
   /// Loads an audio source.
   Future<LoadResponse> load(LoadRequest request) {
     throw UnimplementedError("load() has not been implemented.");
@@ -157,6 +169,17 @@ abstract class AudioPlayerPlatform {
       ConcatenatingMoveRequest request) {
     throw UnimplementedError("concatenatingMove() has not been implemented.");
   }
+
+  /// Starts the visualizer.
+  Future<StartVisualizerResponse> startVisualizer(
+      StartVisualizerRequest request) {
+    throw UnimplementedError("startVisualizer() has not been implemented.");
+  }
+
+  /// Stops the visualizer.
+  Future<StopVisualizerResponse> stopVisualizer(StopVisualizerRequest request) {
+    throw UnimplementedError("stopVisualizer() has not been implemented.");
+  }
 }
 
 /// A playback event communicated from the platform implementation to the
@@ -624,6 +647,53 @@ class ConcatenatingMoveResponse {
       ConcatenatingMoveResponse();
 }
 
+/// Information communicated to the platform implementation when starting the
+/// visualizer.
+class StartVisualizerRequest {
+  final bool enableWaveform;
+  final bool enableFft;
+  final int captureRate;
+  final int captureSize;
+
+  StartVisualizerRequest({
+    @required this.enableWaveform,
+    @required this.enableFft,
+    @required this.captureRate,
+    @required this.captureSize,
+  });
+
+  Map<dynamic, dynamic> toMap() => {
+        'enableWaveform': enableWaveform,
+        'enableFft': enableFft,
+        'captureRate': captureRate,
+        'captureSize': captureSize,
+      };
+}
+
+/// Information returned by the platform implementation after starting the
+/// visualizer.
+class StartVisualizerResponse {
+  final int samplingRate;
+
+  StartVisualizerResponse({@required this.samplingRate});
+
+  static StartVisualizerResponse fromMap(Map<dynamic, dynamic> map) =>
+      StartVisualizerResponse(samplingRate: map['samplingRate']);
+}
+
+/// Information communicated to the platform implementation when stopping the
+/// visualizer.
+class StopVisualizerRequest {
+  Map<dynamic, dynamic> toMap() => {};
+}
+
+/// Information returned by the platform implementation after stopping the
+/// visualizer.
+class StopVisualizerResponse {
+  static StopVisualizerResponse fromMap(Map<dynamic, dynamic> map) =>
+      StopVisualizerResponse();
+}
+
 /// Information about an audio source to be communicated with the platform
 /// implementation.
 abstract class AudioSourceMessage {

just_audio_platform_interface/lib/method_channel_just_audio.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:typed_data';
 
 import 'package:flutter/services.dart';
 
@@ -36,6 +37,18 @@ class MethodChannelAudioPlayer extends AudioPlayerPlatform {
           .receiveBroadcastStream()
           .map((map) => PlaybackEventMessage.fromMap(map));
 
+  @override
+  Stream<Uint8List> get visualizerWaveformStream =>
+      EventChannel('com.ryanheise.just_audio.waveform_events.$id')
+          .receiveBroadcastStream()
+          .cast<Uint8List>();
+
+  @override
+  Stream<Uint8List> get visualizerFftStream =>
+      EventChannel('com.ryanheise.just_audio.fft_events.$id')
+          .receiveBroadcastStream()
+          .cast<Uint8List>();
+
   @override
   Future<LoadResponse> load(LoadRequest request) async {
     return LoadResponse.fromMap(
@@ -134,4 +147,18 @@ class MethodChannelAudioPlayer extends AudioPlayerPlatform {
     return ConcatenatingMoveResponse.fromMap(
         await _channel.invokeMethod('concatenatingMove', request?.toMap()));
   }
+
+  @override
+  Future<StartVisualizerResponse> startVisualizer(
+      StartVisualizerRequest request) async {
+    return StartVisualizerResponse.fromMap(
+        await _channel.invokeMethod('startVisualizer', request?.toMap()));
+  }
+
+  @override
+  Future<StopVisualizerResponse> stopVisualizer(
+      StopVisualizerRequest request) async {
+    return StopVisualizerResponse.fromMap(
+        await _channel.invokeMethod('stopVisualizer', request?.toMap()));
+  }
 }