[Help] BackgroundTask is never executed

[ronaldG19]

Describe the bug
Cloned the example project, it only showed the notification without any controls and the music was not played. Integrated into my own project after 3 days of peeking there is no nay notification bar shown or music played.

Minimal reproduction project

@override
  void initState() {
    WidgetsBinding.instance.addObserver(this);
    map = widget.musicHelper.map;
    _thumPercent = 0.0;
     swiperIndex = widget.musicHelper.index;
     defaultSongIndex = swiperIndex;
      songUrl = widget.musicHelper.map[widget.musicHelper.index]['url'];      
       _controller = PageController(initialPage: swiperIndex);
        _start();
    super.initState();    
  }
  Future<void> _start()async{
    await connect();
    await _initAudioService();
    _servicePlay();
  }
   _initAudioService(){
    AudioService.start(
      backgroundTask:()async{
        _backgroundPlayer();
      },
      resumeOnClick: true,
      androidNotificationChannelName: 'Example Project',
      notificationColor: 0x161b21,
      androidNotificationIcon: 'mipmap/ic_launcher'
    );
    }
  void _backgroundPlayer()async{
    print('background service');
    AudioServiceBackground.run(
      onStart: run,
      onPlay: _play,
      onPause: _pause,
      onStop: _pause,
      onPrepare: _initAudioPlayer
      //onClick: 
    );
  }
  Future<void> run()async{
    print('Audio run service');
    MediaItem mediaItem = MediaItem(
      id: map[swiperIndex]['serial'],
      album: 'Unknown',
      artUri:map[swiperIndex]['cover'],
      title: map[swiperIndex]['name'],
      artist: map[swiperIndex]['by']
    );
    AudioServiceBackground.setMediaItem(mediaItem);
    _play();
    await completer.future;
    _durationSubscription?.cancel();
    _positionSubscription?.cancel();
    _playerStateSubscription?.cancel();
    _playerCompleteSubscription?.cancel();
    _audioServiceSubscription?.cancel();
    //cancelSubscriptions
  }

To Reproduce
Steps to reproduce the behavior:

1. AudioService.connect
2. Started the plugin by AudioService.start
3. BackgroundTask not executed
4. What seems to be errors

SVC-Creating service CreateServiceData{token=android.os.BinderProxy@7f8eced className=com.ryanheise.audioservice.AudioService
packageName=inc.taipan.acapure intent=null}

then

Notification from VM: {streamId: Isolate, event: {type: Event, kind: IsolateStart, isolate: {type: @Isolate, id: isolates/2459700321319607, name: _spawn, number:
2459700321319607}, timestamp: 1569184330328}}
[        ] Sending to VM service: getIsolate({isolateId: isolates/2459700321319607})
[  +56 ms] Result: {type: Isolate, id: isolates/2459700321319607, name: _spawn, number: 2459700321319607, _originNumber: 2459700321319607, startTime: 1569184330293, _heaps: {new:
{type: HeapSpace, name: new, vmName: Scavenger, collections: 0, avgCollectionPeriodMill...
[ +526 ms] Notification from VM: {streamId: Isolate, event: {type: Event, kind: IsolateRunnable, isolate: {type: @Isolate, id: isolates/2459700321319607, name: _spawn, number:
2459700321319607}, timestamp: 1569184330913}}
[        ] Sending to VM service: getIsolate({isolateId: isolates/2459700321319607})
[ +112 ms] Result: {type: Isolate, id: isolates/2459700321319607, name: _spawn, number: 2459700321319607, _originNumber: 969937779835579, startTime: 1569184330294, _heaps: {new:
{type: HeapSpace, name: new, vmName: Scavenger, collections: 0, avgCollectionPeriodMilli...
[ +300 ms] Notification from VM: {streamId: Isolate, event: {type: Event, kind: IsolateExit, isolate: {type: @Isolate, id: isolates/2459700321319607, name: _spawn, number:
2459700321319607}, timestamp: 1569184331325}}

after running flutter run -v

Runtime Environment (please complete the following information):

• Device: Phantom 6 Plus
• Android version: 7

Dependencies used

  line_icons: ^0.2.0
  audioplayers: ^0.13.1
  path_provider:
  http:
  marquee_flutter: ^0.1.4
  sqflite: ^1.1.6+3
  uuid:
  flutter_spinkit:
  cloud_firestore: ^0.12.9
  cached_network_image: ^1.1.1
  data_connection_checker: ^0.3.4
  badges: ^1.1.0
  bottom_navy_bar: ^5.2.0
  shared_preferences: ^0.5.3+4
  flare_flutter: ^1.5.5
  frideos: ^0.7.0+1
  flutter_slidable: ^0.5.3
  flushbar: ^1.8.2
  youtube_player_flutter: ^4.1.0
  path:
  seekbar: ^0.0.2
  firebase_auth: ^0.14.0+4
  google_sign_in: ^4.0.7
  flutter_auth_buttons:
  admob_flutter: ^0.3.1
  onesignal:
  url_launcher: ^5.1.2
  share: ^0.6.2+1
  flare_splash_screen: ^2.1.3
  audio_service: ^0.3.1

Flutter SDK version

[✓] Flutter (Channel dev, v1.10.5, on Linux, locale en_US.UTF-8)
    • Flutter version 1.10.5 at /home/go/Downloads/flutter
    • Framework revision 3cf88fed6d (4 days ago), 2019-09-18 23:09:41 -0400
    • Engine revision 33ad6757e8
    • Dart version 2.6.0 (build 2.6.0-dev.1.0 cb80ea7ba9)

 
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    • Android SDK at /home/go/Android/Sdk
    • Android NDK location not configured (optional; useful for native profiling
      support)
    • Platform android-28, build-tools 28.0.3
    • ANDROID_HOME = /home/go/Android/Sdk
    • Java binary at:
      /home/go/Downloads/android-studio-ide-183.5522156-linux/android-studio/
      jre/bin/java
    • Java version OpenJDK Runtime Environment (build
      1.8.0_152-release-1343-b16-5323222)
    • All Android licenses accepted.

[✓] Android Studio (version 3.4)
    • Android Studio at
      /home/go/Downloads/android-studio-ide-183.5522156-linux/android-studio
    • Flutter plugin version 36.1.1
    • Dart plugin version 183.6270
    • Java version OpenJDK Runtime Environment (build
      1.8.0_152-release-1343-b16-5323222)

[✓] Connected device (1 available)
    • Phantom6 Plus • 0180010710900365 • android-arm64 • Android 7.1.1 (API 25)

• No issues found!

[ryanheise]

If I understand correctly, the supplied example project already exhibits the problem, so I will treat that as your minimal reproduction project.

I tried switching to the dev channel to match your flutter doctor output and ran the example project. I noticed that the notification appears without any controls, but I also noticed this in the console which helps diagnose the problem:

E/flutter ( 4805): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: ServicesBinding.defaultBinaryMessenger was accessed before the binding was initialized.
E/flutter ( 4805): If you're running an application and need to access the binary messenger before `runApp()` has been called (for example, during plugin initialization), then you need to explicitly call the `WidgetsFlutterBinding.ensureInitialized()` first.
E/flutter ( 4805): If you're running a test, you can call the `TestWidgetsFlutterBinding.ensureInitialized()` as the first line in your test's `main()` method to initialize the binding.
E/flutter ( 4805): #0      defaultBinaryMessenger.<anonymous closure> (package:flutter/src/services/binary_messenger.dart:73:7)
E/flutter ( 4805): #1      defaultBinaryMessenger (package:flutter/src/services/binary_messenger.dart:86:4)        
E/flutter ( 4805): #2      MethodChannel.binaryMessenger (package:flutter/src/services/platform_channel.dart:140:62)
E/flutter ( 4805): #3      MethodChannel.setMethodCallHandler (package:flutter/src/services/platform_channel.dart:368:5)
E/flutter ( 4805): #4      new AudioPlayer (package:audioplayer/audioplayer.dart:42:14)                            
E/flutter ( 4805): #5      new CustomAudioPlayer (package:audio_service_example/main.dart:175:34)                  
E/flutter ( 4805): #6      _backgroundAudioPlayerTask (package:audio_service_example/main.dart:162:30)             
E/flutter ( 4805): <asynchronous suspension>                                                                       
E/flutter ( 4805): #7      _runMainZoned.<anonymous closure>.<anonymous closure> (dart:ui/hooks.dart:231:25)       
E/flutter ( 4805): #8      _rootRun (dart:async/zone.dart:1124:13)                                                 
E/flutter ( 4805): #9      _CustomZone.run (dart:async/zone.dart:1021:19)                                          
E/flutter ( 4805): #10     _runZoned (dart:async/zone.dart:1516:10)                                                
E/flutter ( 4805): #11     runZoned (dart:async/zone.dart:1500:12)                                                 
E/flutter ( 4805): #12     _runMainZoned.<anonymous closure> (dart:ui/hooks.dart:223:5)                            
E/flutter ( 4805): #13     _startIsolate.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:305:19)        
E/flutter ( 4805): #14     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:172:12)       

Did you not also get the same error, or are you having a different issue? In the mean time, I'll see if I can fix the above error.

[ronaldG19]

I already resolved that error by initializing WidgetsFlutterBinding.ensureInitialized(), resulted from WidgetBinding.
Notification problem occurred later

[ryanheise]

I don't see the call to 'ensureInitialized' in your minimal reproduction project. audio_service does call this, but since the latest commit on dev, we can see that audio_service does not call this soon enough. You can work around it by calling ensureInitialized yourself as the first line in your background task entrypoint function, but I am working on a proper fix in #86.

But looking at your example code, you need to call the start method with a top level function, not with something like () async { ... }. Documentation here:

https://pub.dev/documentation/audio_service/latest/audio_service/AudioService/start.html

The background task is specified by backgroundTask which will be run within a background isolate. This function must be a top-level or static function

[ryanheise]

@ronaldG19 I've just published 0.4.0 which addresses the ensureInitialized correctly (See #86 and note the changed API). Also let me know after trying it and also making your background task entrypoint into a top level function whether you still get any errors.

[github-actions]

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