audio_service:Flutter 插件可在屏幕关闭时在后台播放音频

# audio_service This plugin wraps around your existing audio code to allow it to run in the background or with the screen turned off, and allows your app to interact with headset buttons, the Android lock screen and notification, iOS control center, wearables and Android Auto. It is suitable for: * Music players * Text-to-speech readers * Podcast players * Video players * Navigators * More! ## How does this plugin work? You encapsulate your audio code in a background task which runs in a special isolate that continues to run when your UI is absent. Your background task implements callbacks to respond to playback requests coming from your Flutter UI, headset buttons, the lock screen, notification, iOS control center, car displays and smart watches:  You can implement these callbacks to play any sort of audio that is appropriate for your app, such as music files or streams, audio assets, text to speech, synthesised audio, or combinations of these. | Feature | Android | iOS | macOS | Web | | ------- | :-------: | :-----: | :-----: | :-----: | | background audio | ✅ | ✅ | ✅ | ✅ | | headset clicks | ✅ | ✅ | ✅ | ✅ | | start/stop/play/pause/seek/rate | ✅ | ✅ | ✅ | ✅ | | fast forward/rewind | ✅ | ✅ | ✅ | ✅ | | repeat/shuffle mode | ✅ | ✅ | ✅ | ✅ | | queue manipulation, skip next/prev | ✅ | ✅ | ✅ | ✅ | | custom actions | ✅ | ✅ | ✅ | ✅ | | custom events | ✅ | ✅ | ✅ | ✅ | | notifications/control center | ✅ | ✅ | ✅ | ✅ | | lock screen controls | ✅ | ✅ | | ✅ | | album art | ✅ | ✅ | ✅ | ✅ | | Android Auto, Apple CarPlay | (untested) | ✅ | | | If you'd like to help with any missing features, please join us on the [GitHub issues page](https://github.com/ryanheise/audio_service/issues). ## Preview the upcoming 0.18.0 release A new version of audio_service is around the corner. This version removes the need for a background isolate, allowing simpler communication between your UI and audio logic, and greater compatibility with plugins that don't support multiple isolates. If you are interested to help with testing or providing feedback, you can upgrade by following the instructions in the [Migration Guide](https://github.com/ryanheise/audio_service/wiki/Migration-Guide#0180-preview). ## Can I make use of other plugins within the background audio task? Yes! `audio_service` is designed to let you implement the audio logic however you want, using whatever plugins you want. You can use your favourite audio plugins such as [just_audio](https://pub.dartlang.org/packages/just_audio), [flutter_radio](https://pub.dev/packages/flutter_radio), [flutter_tts](https://pub.dartlang.org/packages/flutter_tts), and others, within your background audio task. There are also plugins like [just_audio_service](https://github.com/yringler/just_audio_service) that provide default implementations of `BackgroundAudioTask` to make your job easier. Note that this plugin will not work with other audio plugins that overlap in responsibility with this plugin (i.e. background audio, iOS control center, Android notifications, lock screen, headset buttons, etc.) ## Example ### UI code Wrap your `/` route's widget tree in an `AudioServiceWidget`: ```dart void main() => runApp(new MyApp()); class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Audio Service Demo', home: AudioServiceWidget(child: MainScreen()), ); } } ``` Start/stop your background audio task: ```dart await AudioService.start(backgroundTaskEntrypoint: _entrypoint); await AudioService.stop(); ``` Standard controls: ```dart AudioService.play(); AudioService.seekTo(Duration(seconds: 10)); AudioService.setSpeed(1.5); AudioService.pause(); ``` Queue management: ```dart var item = MediaItem( id: 'https://example.com/audio.mp3', album: 'Album name', title: 'Track title', ); AudioService.addQueueItem(item); AudioService.addQueueItemAt(item, 1); AudioService.removeQueueItem(item); AudioService.updateQueue([item, ...]); AudioService.skipToNext(); AudioService.skipToPrevious(); AudioService.playFromMediaId('https://example.com/audio.mp3') AudioService.playMediaItem(item); ``` Looping and shuffling: ```dart AudioService.setRepeatMode(AudioServiceRepeatMode.one); // none/one/all/group AudioService.setShuffleMode(AudioServiceShuffleMode.all); // none/all/group ``` Custom actions: ```dart AudioService.customAction('setVolume', 0.8); AudioService.customAction('saveBookmark'); ``` Listening to state changes: ```dart AudioService.playbackStateStream.listen((PlaybackState state) { if (state.playing) ... else ... switch (state.processingState) { case AudioProcessingState.none: ... case connecting: ... case ready: ... case buffering: ... case fastForwarding: ... case rewinding: ... case skippingToPrevious: ... case skippingToNext: ... case skippingToQueueItem: ... case completed: ... case stopped: ... case error: ... } }); ``` Listen to changes to the currently playing item: ```dart AudioService.currentMediaItemStream.listen((MediaItem item) { ... }); ``` Listen to changes to the queue: ```dart AudioService.queueStream.listen((List<MediaItem> queue) { ... }); ``` Listen to changes to the current playback position: ```dart AudioService.positionStream.listen((Duration position) { ... }); ``` ### Background code Define a background audio task to handle callbacks for all methods called from your UI or other clients (e.g. the media notification): ```dart // Must be a top-level function void _entrypoint() => AudioServiceBackground.run(() => AudioPlayerTask()); class AudioPlayerTask extends BackgroundAudioTask { final _player = AudioPlayer(); // e.g. just_audio // Implement callbacks here. e.g. onStart, onStop, onPlay, onPause } ``` The purpose of this class is to encapsulate all audio logic in your app so that it is completely self-contained, and can continue to run on its own even when the Flutter UI is not present. Every message that you send from your Flutter UI (`start`, `stop`, `play`, `pause`) has a corresponding callback that you can implement in your background audio task (`onStart`, `onStop`, `onPlay`, `onPause`). Additionally, there are callbacks that respond only to events outside of your Flutter UI, such as `onClick`, which responds to a click of a headset button, and `onClose` which responds to the user swiping away the Android media notification. Most of these callbacks can be implemented by simply delegating to your audio player plugin: ```dart onPlay() => _player.play(); onPause() => _player.pause(); onSeekTo(Duration duration) => _player.seekTo(duration); onSetSpeed(double speed) => _player.setSpeed(speed); ``` Your custom actions may be handled via a switch: ```dart onCustomAction(String name, dynamic arguments) async { switch (name) { case 'setVolume': _player.setVolume(arguments); break; case 'saveBookmark': // app-specific code break; } } ``` `onStart` is the place to initialise the player, and (usually) start playing audio: ```dart onStart(Map<String, dynamic> params) async { final mediaItem = MediaItem( id: "https://foo.bar/baz.mp3", album: "Foo", title: "Bar", ); // Tell the UI and