MediaStyle无法正确显示

Question

我正在尝试为我的音乐播放器应用程序创建通知，但是我无法利用媒体样式。首先，我放入setLargeIcon的位图没有出现，通知仅显示按钮（它们起作用）

这是我用来将歌曲的元数据设置为通知的基本方法：

    public static NotificationCompat.Builder from(
        Context context, MediaSessionCompat mediaSession) {
    MediaControllerCompat controller = mediaSession.getController();
    MediaMetadataCompat mediaMetadata = controller.getMetadata();
    MediaDescriptionCompat description = mediaMetadata.getDescription();

    NotificationCompat.Builder builder = new NotificationCompat.Builder(context, "MusicID");
    builder
            .setContentTitle(description.getTitle())
            .setContentText(description.getSubtitle())
            .setSubText(description.getDescription())
            .setLargeIcon(description.getIconBitmap())
            .setContentIntent(controller.getSessionActivity())
            .setVisibility(NotificationCompat.VISIBILITY_PUBLIC);
    return builder;
}

这就是我创建通知的方式

    private Notification showPlayingNotification() {
    NotificationCompat.Builder builder = MediaStyleHelper.from(MediaPlaybackService.this, mMediaSessionCompat);
    if (builder == null) {
        return null;
    }
    builder.addAction(new NotificationCompat.Action(android.R.drawable.ic_media_previous, "Previous", MediaButtonReceiver.buildMediaButtonPendingIntent(this, PlaybackStateCompat.ACTION_SKIP_TO_PREVIOUS)));
    builder.addAction(new NotificationCompat.Action(android.R.drawable.ic_media_pause, "Pause", MediaButtonReceiver.buildMediaButtonPendingIntent(this, PlaybackStateCompat.ACTION_PLAY_PAUSE)));
    builder.addAction(new NotificationCompat.Action(android.R.drawable.ic_media_next, "Next", MediaButtonReceiver.buildMediaButtonPendingIntent(this, PlaybackStateCompat.ACTION_SKIP_TO_NEXT)));
    builder.setStyle(new android.support.v4.media.app.NotificationCompat.MediaStyle().setShowActionsInCompactView(0, 1, 2).setMediaSession(mMediaSessionCompat.getSessionToken()));
    builder.setSmallIcon(R.mipmap.ic_launcher);
    return builder.build();
}

所以问题是我在其他方法中设置的位图根本没有出现，整个样式看起来也很