媒體工作階段回呼在多個 API 中呼叫方法，以控製播放器、管理音訊焦點。
與媒體工作階段和媒體瀏覽器服務通訊請注意，
回應回呼的 MediaSession 邏輯必須一致。行為
回呼不得完全取決於呼叫端的身分，
與具有 MediaSession 的相同應用程式或任何其他應用程式中的活動
「MediaController」已連線至「MediaSession」。
下表摘要說明這些工作如何分配給各個回呼。
| onPlay() | onPause() | onStop() | |
| 音訊焦點 | requestFocus() 傳入您的 OnAudioFocusChangeListener。一律先呼叫 requestFocus()，只有在獲得焦點時才會繼續。
|
abandonAudioFocus()
|
|
| 服務 | startService()
|
stopSelf()
|
|
| 媒體工作階段 | setActive(true)
- 更新中繼資料和狀態 |
- 更新中繼資料和狀態 | setActive(false)
- 更新中繼資料和狀態 |
| 播放器實作 | 啟動播放器 | 暫停播放器 | 停止播放器 |
| 吵雜 | 註冊「BroadcastReceiver」
|
取消註冊「BroadcastReceiver」
|
|
| 通知 | startForeground(notification)
|
stopForeground(false)
|
stopForeground(false)
|
以下是回呼的架構範例：
private val intentFilter = IntentFilter(ACTION_AUDIO_BECOMING_NOISY)
// Defined elsewhere...
private lateinit var afChangeListener: AudioManager.OnAudioFocusChangeListener
private val myNoisyAudioStreamReceiver = BecomingNoisyReceiver()
private lateinit var myPlayerNotification: MediaStyleNotification
private lateinit var mediaSession: MediaSessionCompat
private lateinit var service: MediaBrowserService
private lateinit var player: SomeKindOfPlayer
private lateinit var audioFocusRequest: AudioFocusRequest
private val callback = object: MediaSessionCompat.Callback() {
override fun onPlay() {
val am = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
// Request audio focus for playback, this registers the afChangeListener
audioFocusRequest = AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN).run {
setOnAudioFocusChangeListener(afChangeListener)
setAudioAttributes(AudioAttributes.Builder().run {
setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
build()
})
build()
}
val result = am.requestAudioFocus(audioFocusRequest)
if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
// Start the service
startService(Intent(context, MediaBrowserService::class.java))
// Set the session active (and update metadata and state)
mediaSession.isActive = true
// start the player (custom call)
player.start()
// Register BECOME_NOISY BroadcastReceiver
registerReceiver(myNoisyAudioStreamReceiver, intentFilter)
// Put the service in the foreground, post notification
service.startForeground(id, myPlayerNotification)
}
}
public override fun onStop() {
val am = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
// Abandon audio focus
am.abandonAudioFocusRequest(audioFocusRequest)
unregisterReceiver(myNoisyAudioStreamReceiver)
// Stop the service
service.stopSelf()
// Set the session inactive (and update metadata and state)
mediaSession.isActive = false
// stop the player (custom call)
player.stop()
// Take the service out of the foreground
service.stopForeground(false)
}
public override fun onPause() {
val am = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
// Update metadata and state
// pause the player (custom call)
player.pause()
// unregister BECOME_NOISY BroadcastReceiver
unregisterReceiver(myNoisyAudioStreamReceiver)
// Take the service out of the foreground, retain the notification
service.stopForeground(false)
}
}
private IntentFilter intentFilter = new IntentFilter(AudioManager.ACTION_AUDIO_BECOMING_NOISY);
// Defined elsewhere...
private AudioManager.OnAudioFocusChangeListener afChangeListener;
private BecomingNoisyReceiver myNoisyAudioStreamReceiver = new BecomingNoisyReceiver();
private MediaStyleNotification myPlayerNotification;
private MediaSessionCompat mediaSession;
private MediaBrowserService service;
private SomeKindOfPlayer player;
private AudioFocusRequest audioFocusRequest;
MediaSessionCompat.Callback callback = new
MediaSessionCompat.Callback() {
@Override
public void onPlay() {
AudioManager am = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
// Request audio focus for playback, this registers the afChangeListener
AudioAttributes attrs = new AudioAttributes.Builder()
.setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
.build();
audioFocusRequest = new AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN)
.setOnAudioFocusChangeListener(afChangeListener)
.setAudioAttributes(attrs)
.build();
int result = am.requestAudioFocus(audioFocusRequest);
if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
// Start the service
startService(new Intent(context, MediaBrowserService.class));
// Set the session active (and update metadata and state)
mediaSession.setActive(true);
// start the player (custom call)
player.start();
// Register BECOME_NOISY BroadcastReceiver
registerReceiver(myNoisyAudioStreamReceiver, intentFilter);
// Put the service in the foreground, post notification
service.startForeground(id, myPlayerNotification);
}
}
@Override
public void onStop() {
AudioManager am = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
// Abandon audio focus
am.abandonAudioFocusRequest(audioFocusRequest);
unregisterReceiver(myNoisyAudioStreamReceiver);
// Stop the service
service.stopSelf();
// Set the session inactive (and update metadata and state)
mediaSession.setActive(false);
// stop the player (custom call)
player.stop();
// Take the service out of the foreground
service.stopForeground(false);
}
@Override
public void onPause() {
AudioManager am = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
// Update metadata and state
// pause the player (custom call)
player.pause();
// unregister BECOME_NOISY BroadcastReceiver
unregisterReceiver(myNoisyAudioStreamReceiver);
// Take the service out of the foreground, retain the notification
service.stopForeground(false);
}
};