audio_service 0.3.1

Flutter plugin to play audio in the background while the screen is off.

audio_service

Play audio in the background.

• Continues playing while the screen is off or the app is in the background
• Control playback from your Flutter UI, headset, Wear OS or Android Auto
• Drive audio playback from Dart code

This plugin provides a complete framework for playing any audio in the background. You implement callbacks in Dart to play/pause/seek/etc audio in the background giving you the flexibility to use any Dart plugin and any custom Dart logic to output the audio. For example, if you wish to play music in the background, you may use the audioplayer plugin in conjunction with audio_service. If you would rather play text-to-speech in the background, you may use the flutter_tts plugin in conjunction with audio_service.

audio_service itself manages all of the platform-specific code for setting up the environment for background audio, and interfacing with various peripherals used to control audio playback. For Android, this means acquiring a wake lock so that audio will play with the screen turned off, acquiring audio focus so that your app can gracefully handle phone call interruptions, creating a media session and media browser service so that your app can be controlled by wearable devices and Android Auto. The iOS side is currently not implemented and contributors are welcome (please see the Help section at the bottom of this page).

Since background execution of Dart code is a relatively new feature of Flutter, not all plugins are yet compatible with audio_service (I am contacting some of these authors to make their packages compatible.)

Example

Client-side code

This code runs in the main UI isolate.

AudioService.connect();    // When UI becomes visible
AudioService.start(        // When user clicks button to start playback
  backgroundTask: myBackgroundTask,
  androidNotificationChannelName: 'Music Player',
  androidNotificationIcon: "mipmap/ic_launcher",
);
AudioService.pause();      // When user clicks button to pause playback
AudioService.play();       // When user clicks button to resume playback
AudioService.disconnect(); // When UI is gone

Background code

This code runs in a background isolate.

void myBackgroundTask() {
  AudioServiceBackground.run(
    onStart: () async {
      // Your custom dart code to start audio playback.
      // NOTE: The background audio task will shut down
      // as soon as this async function completes.
    },
    onPlay: () {
      // Your custom dart code to resume audio playback.
    },
    onPause: () {
      // Your custom dart code to pause audio playback.
    },
    onStop: () {
      // Your custom dart code to stop audio playback.
    },
    onClick: (MediaButton button) {
      // Your custom dart code to handle a media button click.
    },
  );
}

Android setup

You will need to create a custom MainApplication class as follows:

public class MainApplication extends FlutterApplication implements PluginRegistry.PluginRegistrantCallback {
  @Override
  public void onCreate() {
    super.onCreate();
    AudioServicePlugin.setPluginRegistrantCallback(this);
  }

  @Override
  public void registerWith(PluginRegistry registry) {
    GeneratedPluginRegistrant.registerWith(registry);
  }
}

Edit your project's AndroidManifest.xml file to reference your MainApplication class, declare the permission to create a wake lock, and add component entries for the <service> and <receiver>:

<manifest ...>
  <uses-permission android:name="android.permission.WAKE_LOCK"/>
  <uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>
  
  <application
    android:name=".MainApplication"
    ...>
    
    ...
    
    <service android:name="com.ryanheise.audioservice.AudioService">
      <intent-filter>
        <action android:name="android.media.browse.MediaBrowserService" />
      </intent-filter>
    </service>

    <receiver android:name="androidx.media.session.MediaButtonReceiver" >
      <intent-filter>
        <action android:name="android.intent.action.MEDIA_BUTTON" />
      </intent-filter>
    </receiver> 
  </application>
</manifest>

Any icons that you want to appear in the notification (see the MediaControl class) should be defined as Android resources in android/app/src/main/res. Here you will find a subdirectory for each different resolution:

drawable-hdpi
drawable-mdpi
drawable-xhdpi
drawable-xxhdpi
drawable-xxxhdpi

You can use Android Asset Studio to generate these different subdirectories for any standard material design icon.

Help/Contribute

• If you would like to contribute to the iOS side, please see https://github.com/ryanheise/audio_service/issues/10 for a description of the work to be done, and read or contribute to the ongoing discussion on how we could make this work.

• If you find another Flutter plugin (audio or otherwise) that crashes when running in the background environment, another way you can help is to file a bug report with that project, letting them know of the simple fix to make it work (see below).

Sample bug report

Here is a sample bug report.

Flutter's new background execution feature (described here: https://medium.com/flutter-io/executing-dart-in-the-background-with-flutter-plugins-and-geofencing-2b3e40a1a124) allows plugins to be registered in a background context (e.g. a Service). The problem is that the wifi plugin assumes that the context for plugin registration is an activity with this line of code:

WifiManager wifiManager = (WifiManager) registrar.activity().getApplicationContext().getSystemService(Context.WIFI_SERVICE);

registrar.activity() may now return null, and this leads to a NullPointerException:

E/AndroidRuntime( 2453):   at com.ly.wifi.WifiPlugin.registerWith(WifiPlugin.java:23)
E/AndroidRuntime( 2453):   at io.flutter.plugins.GeneratedPluginRegistrant.registerWith(GeneratedPluginRegistrant.java:30)

The solution is to change the above line of code to this:

WifiManager wifiManager = (WifiManager) registrar.activeContext().getApplicationContext().getSystemService(Context.WIFI_SERVICE);