如何堆叠Firebase通知？

Question

我想要堆叠Firebase通知。我尝试了post中的那个，但它没有用。

我该怎么做？这是我的代码。感谢。

public class FirebaseMessagingService extends FirebaseMessagingService {
    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        showNotification(remoteMessage.getData().get("message"));
    }

    private void showNotification(String message) {

        Intent i = new Intent(this,MainActivity.class);
        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

        PendingIntent pendingIntent = PendingIntent.getActivity(this,0,i,PendingIntent.FLAG_UPDATE_CURRENT);        
        NotificationCompat.Builder builder = new NotificationCompat.Builder(this)
                .setAutoCancel(true)
                .setContentTitle("test")
                .setContentText(message)                
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentIntent(pendingIntent);

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