Media Session Callbacks
一旦是视频app在同一个activity中运行媒体会话和媒体控制器，媒体会话回调的实现与音频应用server/client 架构实现的回调不同。由于没有服务的调用，所以notification都是由NotificationManager来控制的。下面的列表展示两种回调函数中不同的控制方式。
| _ | onPlay() | onPause() | onStop() |
|---|---|---|---|
| Audio Focus | requestFocus() passing in your OnAudioFocusChangeListener. Always call requestFocus() first, proceed only if focus is granted. | abandonAudioFocus() | |
| Media Session | setActive(true) - Update metadata and state | -Update metadata and state | setActive(false) - Update metadata and state |
| Player Implementation | Start the player | Pause the player | Stop the player |
| Becoming Noisy | Register your BroadcastReceiver | Unregister your BroadcastReceiver | |
| Notifications | Show notification | Update notification | Cancel notification |