Android Notifications

 public void createNotification(View view) {
        // Prepare intent which is triggered if the
        // notification is selected
        Intent intent = new Intent(this, NotificationReceiverActivity.class);
        PendingIntent pIntent = PendingIntent.getActivity(this, (int) System.currentTimeMillis(), intent, 0);

        // Build notification
        // Actions are just fake
        Notification noti = new Notification.Builder(this)
                .setContentTitle("New mail from " + "[email protected]")
                .setContentText("Subject")
                .setSmallIcon(R.drawable.icon)
                .setContentIntent(pIntent)
                .setTicker("Subject")
                .addAction(R.drawable.icon, "Call", pIntent)
                .addAction(R.drawable.icon, "More", pIntent)
                .addAction(R.drawable.icon, "And more", pIntent).build();
        NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        // hide the notification after its selected
        noti.flags |= Notification.FLAG_AUTO_CANCEL;

        notificationManager.notify(0, noti);

    }

or start foreground service

startForeground(101,notification);

References
http://www.vogella.com/tutorials/AndroidNotifications/article.html
https://questdot.com/android-foreground-service/

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