MediaSessionCompat问题在重新获得音频焦点后不起作用

Question

这是MediaSessionCompat代码，仅用于媒体按钮控制，不适用于传输控制，

mediaSessionCompat=new MediaSessionCompat(this,"simple_music_button_control");
mediaSessionCallback = new MediaSessionCompat.Callback() {
            @Override
            public boolean onMediaButtonEvent(Intent mediaButtonEvent) {
                ...
            }
        };
mediaSessionCompat.setCallback(mediaSessionCallback);
mediaSessionCompat.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS);
mediaSessionCompat.setActive(true);

这是音频焦点代码，

...
if (focusChange == AudioManager.AUDIOFOCUS_GAIN) {
    Log.e("media session",mediaSessionCompat.isActive()?"true":"false");
    mediaSessionCompat.setActive(true);
    if (!manual_pause) {
        if (media_player_state == media_player_pausing) {
            if (media_player != null)
                media_player.start();
            media_player_state = media_player_playing;
            Intent resume_music_intent = new Intent("resume_song_intent");
            LocalBroadcastManager.getInstance(ServiceMusicPlay.this).sendBroadcast(resume_music_intent);
            notification = notificationMusicPlay.buildNotification(current_play_song, media_player_state);
            startForeground(notification_id, notification);
           }
        }
     } 

问题是重新获得音频焦点（例如从MX Video Player重新获得音频）后，媒体控制将无法工作。重新获取音频焦点时，正在检查mediaSessionCompat，它不是null，并且isActive为true，但是media按钮将不起作用！

感谢您的帮助！