Flutter listeners keep listening to old events every time the page is rebuilt - flutter

Question

I am currently developing an order management app for a restaurant, in which users can place orders through the app. Once orders are placed, an admin (restaurant manager) can accept orders on the admin portal, and the user will be notified to go pick up their food when the order is completed.
I am using flutter's "awesome notifications" package to handle notifications.
In the method below, I am essentially listening for new entries into the "ManagedOrders" table of our database (firebase real time database). Accepted orders are moved into this table, therefore I want to notify the user that their order has been accepted if the order moved into this table contains a customerID equal to the customerID of the user currently logged in.
import 'dart:async';
import 'package:firebase_database/firebase_database.dart';
import '../models/notifications.dart';
final DatabaseReference _dbRef = FirebaseDatabase.instance.ref();
late StreamSubscription _orderStream;
String loggedInUserID = "9ibdsUENaAdnpA3qxm35Y8xRe9F3"; //Hard coded for now
Map<dynamic, dynamic> databaseMapper = {};
List<String> placedOrderIDsList = [];
void listenForAcceptedOrders() async {
//This method listens for accepted orders and displays a notification
//It checks for new records entered into the managedOrders table containing the same customerID as the user currently logged in.
//If the customerID matches the ID of the current user logged in, it means that an order placed by THIS user has been accepted.
_orderStream = _dbRef.child("ManagedOrders").onChildAdded.listen((event) {
databaseMapper = event.snapshot.value as Map;
String customerID = databaseMapper["customerID"].toString();
print("CUSTOMERID ______......>>" + customerID);
if (customerID == loggedInUserID) {
acceptedOrderNotification(); //A notification defined in another class
} else {
print("NO MATCH FOUND");
}
});
//_orderStream.cancel();
}
I then call this method in my homescreen in the initState method:
listenForAcceptedOrders();
The issue I am having is once a record is added to the "ManagedOrders" table with a customerID that matches the ID of the user logged in, I continue to receive the notification every time I navigate back to the home page, even if I delete the record from the "ManagedOrders" table.
I tried to cancel the listeners at the end of the "listenForAcceptedOrders()" method, but that results in no listeners at all (I.E adding a record to the "ManagedOrders" table does not trigger any notification).
How do I make it so that the user can receive the notification once, and not have it repeat every time they navigate to the home page?
Any help would be much appreciated!

Answer 1

just add a bool variable and set it to true once you receive the notification so it will not repeat it self again
Look the correct code below:
import 'dart:async';
import 'package:firebase_database/firebase_database.dart';
import '../models/notifications.dart';
final DatabaseReference _dbRef = FirebaseDatabase.instance.ref();
bool example = false;
late StreamSubscription _orderStream;
String loggedInUserID = "9ibdsUENaAdnpA3qxm35Y8xRe9F3"; //Hard coded fornow
Map<dynamic, dynamic> databaseMapper = {};
List<String> placedOrderIDsList = [];
void listenForAcceptedOrders() async {
_orderStream = _dbRef.child("ManagedOrders").onChildAdded.listen((event) {
databaseMapper = event.snapshot.value as Map;
String customerID = databaseMapper["customerID"].toString();
print("CUSTOMERID ______......>>" + customerID);
if (customerID == loggedInUserID) {
if(example = false){
acceptedOrderNotification(); //A notification defined in another class
example = true;
}
} else {
print("NO MATCH FOUND");
}
});
//_orderStream.cancel();
}