android中聊天应用的通知

我如何在android聊天应用程序中获得通知。。。。 NotificationCompat.Builder nBuilder=新的NotificationCompat.Builder（此）

我正在我的主要活动中使用此代码。当我们单击通知时，我想打开相同的活动

    Intent intent = new Intent(this, MainActivity.class);
    intent.setData(myUri);
    TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);
    stackBuilder.addParentStack(MainActivity.class);
    stackBuilder.addNextIntent(intent);
    PendingIntent resultPendingIntent = stackBuilder.getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);
    Uri alarmSound = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
    new NotificationCompat.Builder(this)
            .setSmallIcon(R.mipmap.ic_launcher)
            .setAutoCancel(true)
            .setContentIntent(resultPendingIntent)
            .setContentTitle(notificationData.Title)
            .setSound(alarmSound)
            .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.mipmap.ic_notification))
            .setContentText(notificationData.Description)
            .setStyle(notiStyle).build();

 PendingIntent nPendingInten=nStackBuilder.getPendingIntent(0,PendingIntent.FLAG_UPDATE_CURRENT);

与

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单击通知后是否要打开MainActivity？

 PendingIntent nPendingInten=nStackBuilder.getPendingIntent(0,PendingIntent.FLAG_UPDATE_CURRENT);

PendingIntent nPendingInten= PendingIntent.getActivity(this, 0, nIntent,
                PendingIntent.FLAG_UPDATE_CURRENT);