NotificationCompat不分组通知

Question

我试图对我的通知进行分组，但显然他们会分开来。

NotificationManager mNotificationManager = (NotificationManager)
this.getSystemService(Context.NOTIFICATION_SERVICE);

Intent resultIntent = new Intent(this, SplashScreenBaseActivity.class);
resultIntent.putExtra(Arguments.ARG_NOTIFICATION_TYPE, NEWS_TYPE);
TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);
stackBuilder.addNextIntent(resultIntent);
PendingIntent resultPendingIntent =
        stackBuilder.getPendingIntent(
                0,
                PendingIntent.FLAG_UPDATE_CURRENT
        );

NotificationCompat.Builder mBuilder =
        new NotificationCompat.Builder(this)
                .setSmallIcon(R.drawable.ic_launcher_small)
                    .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher))
                    .setContentTitle(contentTitle)
                    .setContentText(contentText)
                    .setAutoCancel(true)
                    .setGroup(NEWS_GROUP)
                    .setGroupSummary(true)
                    .setDefaults(-1);

mBuilder.setContentIntent(resultPendingIntent);

Random random = new Random();
NOTIFICATION_ID = random.nextInt(9999 - 1000) + 1000;
mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());