How to prevent notifications being overwritten each time a new notification is created?

Question

I am trying to send a notification at a specific time after registering an item on a database (6 hours or 12 hours). The notification works fine when I only register one item, however if I register 2 items in a close period of time the first notification is overwritten by the second.

I know that I have to add ID's to the pending intents and maybe an id to the actual notification however I am not very familiar with the alarmManager class and I do not know where I should be adding the IDs. How do I make these two notifications independent of one another?

NotificationHelper Class:

public static class NotificationHelper extends ContextWrapper {

        public static final String channel1ID = "channel1ID";
        public static final String channel1Name = "USER1";

        private NotificationManager mManager;


        public NotificationHelper(Context base) {
            super(base);
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                createChannels();
            }
        }

        @RequiresApi(api = Build.VERSION_CODES.O)
        private void createChannels() {

            NotificationChannel channel1 = new NotificationChannel(channel1ID, channel1Name, NotificationManager.IMPORTANCE_HIGH);
            channel1.enableLights(true);
            channel1.enableVibration(true);
            channel1.shouldVibrate();
            channel1.setShowBadge(true);
            channel1.setLightColor(R.color.colorPrimary);
            channel1.setLockscreenVisibility(Notification.VISIBILITY_PUBLIC);
            Uri uri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
            AudioAttributes audioAttributes = new AudioAttributes.Builder()
                    .setContentType(AudioAttributes.CONTENT_TYPE_UNKNOWN)
                    .setUsage(USAGE_NOTIFICATION)
                    .build();
            channel1.setSound(uri, audioAttributes);

            getManager().createNotificationChannel(channel1);


        }

        public NotificationManager getManager() {
            if (mManager == null) {
                mManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            }
            return mManager;
        }


        public NotificationCompat.Builder getChannel1Notification() {
            return new NotificationCompat.Builder(getApplicationContext(), channel1ID)
                    .setContentTitle("Dressing")
                    .setContentText("Please scan the dressing on your: " + (et_DressingPos.getText().toString().trim()))
                    .setSmallIcon(R.drawable.ic_cnoticiation_scan);


        }


    }

AlarmReceiver Class:

 @Override
    public void onReceive(Context context, Intent intent) {
        Camera2Register.NotificationHelper notificationHelper = new Camera2Register.NotificationHelper(context);
        NotificationCompat.Builder nb = notificationHelper.getChannel1Notification();
        Intent intent2 = new Intent(context, Camera2.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(context, 1, intent2, 0);
        nb.setContentIntent(pendingIntent);
        notificationHelper.getManager().notify(1, nb.build());
    }
}

startAlarmScan and startALarmChange Methods:

private void startAlarmScan() {
        int requestCode = ("someString" + System.currentTimeMillis()).hashCode();

        Long time = System.currentTimeMillis();

        AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        Intent intent = new Intent(this, AlarmReceiver.class);
        intent.putExtra("randomRequestCode", requestCode);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(this, requestCode, intent, 0);

        long milliseconds = 5000;
        alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, (time + milliseconds), pendingIntent);

        //}
    }

    private void startAlarmChange() {
        int requestCode = ("someString" + System.currentTimeMillis()).hashCode();

        Long time = System.currentTimeMillis();
        AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        Intent intent = new Intent(this, AlarmReceiver.class);
        intent.putExtra("randomRequestCode", requestCode);

        PendingIntent pendingIntent = PendingIntent.getBroadcast(this, requestCode, intent, 0);

        long milliseconds = 30000;

            alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, (time + milliseconds), pendingIntent2);
        //}
    }

I have set the time delay for the two different notifications to 5 and 30 seconds. If register and class the two startAlarmScan and startAlarmChange methods within 30 seconds of each other. the first scheduled notification will be overwritten by the second.

I am beginning to think the problem may lie in the structuring of my notification system, is a Receiver class necessary? There is no mention of it in the notification documentation on Android.

Answer 1

You are using a constant value "1" for your notification id here: notificationHelper.getManager().notify(1, nb.build());

from the docs: Here "If a notification with the same id has already been posted by your application and has not yet been canceled, it will be replaced by the updated information"

Change this 1 to a unique number for each notification and you should see them all come through.

Edit You also do the same thing on the line:

PendingIntent pendingIntent = PendingIntent.getActivity(context, 1, intent2, 0);

That request code "1" is used to compare pending intents using filterEquals(Intent intent) This question talks about it.