Intent i = new Intent(getBaseContext(), MyReceiver.class);
 PendingIntent pi = PendingIntent.getBroadcast(MainActivity.this, 100,i, PendingIntent.FLAG_UPDATE_CURRENT);
                AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
                alarmManager.set(AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + 5000, pi);
            }
        });
    }
private void  create()
{
    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
        String tag="mm";
        Log.d(tag,"xyz");
        NotificationChannel notificationChannel = new NotificationChannel("abc","abc",NotificationManager.IMPORTANCE_HIGH);
        NotificationManager notificationManager =  getSystemService(NotificationManager.class);
        notificationManager.createNotificationChannel(notificationChannel);
    }
//Receiver class
public class MyReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
    NotificationCompat.Builder notification  = new NotificationCompat.Builder(context,"abc")
            .setContentTitle("Title")
            .setContentText("text")
            .setPriority(NotificationManager.IMPORTANCE_HIGH)
            .setSmallIcon(R.drawable.ic_launcher_background);
    NotificationManagerCompat notificationManagerCompat = NotificationManagerCompat.from(context);
    notificationManagerCompat.notify(1,notification.build());
}
}
Manifest file is updated also. I've called create function in onCreate. If anyone can help me. I've been stuck on this for a week