PlayerNotificationManager不显示在android exoplayer上播放视频的通知？

我的应用程序播放视频

我正在关注这一点

代码相同

 PlayerNotificationManager playerNotificationManager = new PlayerNotificationManager(
            appCMSPresenter.getCurrentContext(),
            "kingkdfn",
            459, new DescriptionAdapter());

    playerNotificationManager.setPlayer(getPlayer());

描述适应器

public class DescriptionAdapter implements
    PlayerNotificationManager.MediaDescriptionAdapter {

@Override
public String getCurrentContentTitle(Player player) {
    int window = player.getCurrentWindowIndex();
    return "getTitle(window)";
}

@Nullable
@Override
public String getCurrentContentText(Player player) {
    int window = player.getCurrentWindowIndex();
    return "getDescription(window)";
}

@Nullable
@Override
public Bitmap getCurrentLargeIcon(Player player,
                                  PlayerNotificationManager.BitmapCallback callback) {

    return null;
}

@Nullable
@Override
public PendingIntent createCurrentContentIntent(Player player) {
    return null;
}
}

全部添加到舱单中

<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />

但在播放视频时，仍不会显示通知。 我需要补充什么吗