媒体会话回调

您的媒体会话回调调用多个 API 中的方法,以控制播放器、管理音频焦点、 并与媒体会话和媒体浏览器服务进行通信。请注意, 响应回调的 MediaSession 逻辑必须保持一致。行为 调用方不得依赖于调用方的身份, 同一应用中运行 MediaSession 的 activity 或任何其他具有 MediaController已连接到MediaSession

下表总结了这些任务在回调中的分布情况。

onPlay() onPause() onStop()
音频焦点 requestFocus() 传入您的 OnAudioFocusChangeListener
始终先调用 requestFocus(),仅在获得焦点时继续。
abandonAudioFocus()
服务 startService() stopSelf()
媒体会话 setActive(true)
- 更新元数据和状态
- 更新元数据和状态 setActive(false)
- 更新元数据和状态
播放器实现 启动播放器 暂停播放器 停止播放器
发出噪音 注册您的BroadcastReceiver 取消注册您的BroadcastReceiver
通知 startForeground(notification) stopForeground(false) stopForeground(false)

以下是回调的示例框架:

KotlinJava
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);
       
}
   
};