How to use

onMetadataChanged

method

in

android.support.v4.media.session.MediaControllerCompat$Callback

@Override
public void onMetadataChanged(MediaMetadataCompat metadata) {
  super.onMetadataChanged(metadata);
  mMetadata = metadata;
  Notification notification = createNotification();
  if (notification != null) {
    mNotificationManager.notify(NOTIFICATION_ID, notification);
  }
}

@Override
public void onMetadataChanged(MediaMetadataCompat metadata) {
  super.onMetadataChanged(metadata);
  mMetadata = metadata;
  Notification notification = createNotification();
  if (notification != null) {
    mNotificationManager.notify(NOTIFICATION_ID, notification);
  }
}

  @Override
  public void perform(@NonNull Callback callback) {
    callback.onMetadataChanged(metadata);
  }
});

@Override
public void onMetadataChanged(MediaMetadataCompat metadata) {
  super.onMetadataChanged(metadata);
  nowPlaying = metadata != null ? metadata : NOTHING_PLAYING;
  //状态监听
  CopyOnWriteArrayList<OnPlayerEventListener> mPlayerEventListeners = MusicManager.getInstance().getPlayerEventListeners();
  if (metadata != null) {
    SongInfo songInfo = null;
    for (OnPlayerEventListener listener : mPlayerEventListeners) {
      List<SongInfo> songInfos = MusicProvider.getInstance().getSongInfos();
      for (SongInfo info : songInfos) {
        if (info.getSongId().equals(metadata.getString(MediaMetadataCompat.METADATA_KEY_MEDIA_ID))) {
          songInfo = info;
          break;
        }
      }
      listener.onMusicSwitch(songInfo);
    }
  }
}

public void registerCallback(Callback callback) {
  if (callback != null) {
    mCallbackList.add(callback);
    // Update with the latest metadata/playback state.
    if (mMediaController != null) {
      final MediaMetadataCompat metadata = mMediaController.getMetadata();
      if (metadata != null) {
        callback.onMetadataChanged(metadata);
      }
      final PlaybackStateCompat playbackState = mMediaController.getPlaybackState();
      if (playbackState != null) {
        callback.onPlaybackStateChanged(playbackState);
      }
    }
  }
}

  @Override
  public void onMetadataChanged(Object metadataObj) {
    Callback.this.onMetadataChanged(
        MediaMetadataCompat.fromMediaMetadata(metadataObj));
  }
}

@Override
public void onMetadataChanged(MediaMetadataCompat metadata) {
  super.onMetadataChanged(metadata);
  final int max = metadata != null
      ? (int) metadata.getLong(MediaMetadataCompat.METADATA_KEY_DURATION)
      : 0;
  setProgress(0);
  setMax(max);
}