如何在使用firebase notifiaction的应用程序后台显示BigPictureStyle通知？

public class MyFirebaseMessagingService extends FirebaseMessagingService {

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        if (remoteMessage.getNotification() != null && remoteMessage.getData().containsKey("big_picture")) {
            String title = remoteMessage.getNotification().getTitle();
            String message = remoteMessage.getNotification().getBody();
            String imageUrl = remoteMessage.getData().get("big_picture");

            Bitmap bitmap = getBitmapFromUrl(imageUrl);

            NotificationCompat.Builder builder = new NotificationCompat.Builder(this)
                    .setContentTitle(title)
                    .setContentText(message)
                    .setSmallIcon(R.drawable.ic_notification)
                    .setLargeIcon(bitmap)
                    .setStyle(new NotificationCompat.BigPictureStyle().bigPicture(bitmap));

            NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            notificationManager.notify(0, builder.build());
        }
    }

    private Bitmap getBitmapFromUrl(String imageUrl) {
        // 从网络或本地资源获取图片，并返回Bitmap对象
        // 这里只是一个示例，你需要根据实际情况实现该方法
        return null;
    }
}