安卓MediaRouter卷事件

Question

我想实现在Youtube应用中看到的音量变化，就像应用程序在后台或锁定屏幕上一样。

像这样

private void createSession() {
    ComponentName receiver = new ComponentName(getPackageName(), RemoteReceiver.class.getName());
    mediaSession = new MediaSessionCompat(this, "PlayerService", receiver, null);
    mediaSession.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS |
            MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
    mediaSession.setPlaybackState(new PlaybackStateCompat.Builder()
            .setState(PlaybackStateCompat.STATE_PLAYING, 0, 1f)
            .setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE)
            .build());
    AudioManager audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
    audioManager.requestAudioFocus(new AudioManager.OnAudioFocusChangeListener() {
        @Override
        public void onAudioFocusChange(int focusChange) {
            // Ignore
        }
    }, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);
    mediaSession.setActive(true);

    mediaRouter = MediaRouter.getInstance(this);
    mediaRouter.setMediaSessionCompat(mediaSession);
}

现在，我得到了滑块，就像上面的图像，它响应音量按钮，但我没有收到我的广播接收器的变化。

Answer 1

您所要做的就是用一个MediaSessionCompat创建一个VolumeProviderCompat。

// Here is a volume provider which sets the volume of a remote route.
// Extend VolumeProviderCompat with your own implementation.
public static class RemoteVolume extends VolumeProviderCompat {
    public RemoteVolume(MediaRouter.RouteInfo routeInfo) {
        super(VolumeProviderCompat.VOLUME_CONTROL_ABSOLUTE, STEPS, 0);
        this.stepSize = routeInfo.getVolumeMax() / STEPS;
        this.routeInfo = routeInfo;
    }

    @Override
    public void onSetVolumeTo(int volume) {
        routeInfo.requestSetVolume(volume * stepSize);
        setCurrentVolume(volume);
    }

    @Override
    public void onAdjustVolume(int delta) {
        int newVolume = getCurrentVolume() + delta;
        routeInfo.requestSetVolume(newVolume * stepSize);
        setCurrentVolume(newVolume);
    }
}

然后，将VolumeProviderCompat连接到您的MediaSessionCompat

MediaSessionCompat session = new MediaSessionCompat(context, TAG);

// might need some of these flags
session.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS |
            MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS |
            MediaSessionCompat.FLAG_HANDLES_QUEUE_COMMANDS);

// the volume buttons are routed to this session when it is
// active and currently playing
session.setPlaybackState(new PlaybackStateCompat.Builder()
        .setState(PlaybackStateCompat.STATE_PLAYING, 0, 1.0f)
        .build());

session.setActive(true);

// The media router tries to bind its own VolumeProvider which kinda
// works. We need to unbind the one provided and put ours in.
router.setMediaSessionCompat(session);
session.setPlaybackToRemote(new RemoteVolume(myRemoteRoute));