How can I keep a variable value inside an isolate/FlutterBackgroundService?

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I'm currently working on implementing an isolate with a notification handler in Flutter.
Flutter
It's already working, I have a MQTT listener that shows a notification using AwesomeNotification with 2 actions for accepting or rejecting the notification.
MQTT
AwesomeNotification
When a notification is accepted, I want to make an API call to update the record related to that notification.
To make it a bit easy for me, I included some details with the MQTT payload that I need to use to make the API call, I set that detail to a variable so I can use it later on.
MQTT
The problem is that when the app reaches AwesomeNotification's onActionReceivedMethod, the variable's value is already gone.
AwesomeNotification's onActionReceivedMethod
I think the reason for this is because, down the line, the executing code is already outside the scope of the service/isolate so the variable can't be reached already.
service/isolate
I then tried to use SharedPreferences, but a key doesn't get updated as fast as I wanted/expected it to be. Now, I'm at a loss as to how I could keep a bit of value around so I could proceed with the process.
SharedPreferences
Here's my current code:
import 'dart:async';
import 'dart:convert';
import 'dart:developer';
import 'dart:isolate';
import 'dart:ui';

import 'package:baraco_frontend/helpers/api/request_vehicle_change_api_helper.dart';
import 'package:baraco_frontend/helpers/sharedPref/shared_pref_helper.dart';
import 'package:flutter/material.dart';
import 'package:flutter_background_service/flutter_background_service.dart';
import 'package:intl/intl.dart';
import 'package:mqtt_client/mqtt_client.dart';
import 'package:vibration/vibration.dart';
import 'package:awesome_notifications/awesome_notifications.dart';

import '../globals.dart';
import '../models/user.dart';
import 'mqtt_helper.dart';

final _service = FlutterBackgroundService();
String notifTxt = 'Waiting for notification';
const String approveKey = 'approve';
const String rejectKey = 'reject';
const String approveLabel = 'Approve';
const String rejectLabel = 'Reject';
String _requestVehicleChangeId = '';
ReceivePort processRequestVehicleChangeRecvPort = ReceivePort('processRequestVehicleChangeRecv');

Future void initializeService() async{
log('initializeService');
await _service.configure(
androidConfiguration: AndroidConfiguration(
autoStart: true,
onStart: _onServiceStart,
isForegroundMode: true,
),
iosConfiguration: IosConfiguration(
autoStart: true,
onForeground: _onServiceStart,
onBackground: _onServiceIosBackground,
),
);

await initializeLocalNotifications();
await initializeIsolateReceivePort();
startListeningNotificationEvents();
}

@pragma('vm:entry-point')
Future void _onServiceStart(ServiceInstance service) async {
DartPluginRegistrant.ensureInitialized();
log('service started');

if (service is AndroidServiceInstance) {
service.on('setAsForeground').listen((ev) {
service.setAsForegroundService();
});
service.on('setAsBackground').listen((ev) {
service.setAsBackgroundService();
});
}

service.on('stopService').listen((ev) {
service.stopSelf();
});

MqttHelper().connect().then((val) async {
var user = User.fromJson( jsonDecode(await SharedPrefHelper().getPrefWithKey( Globals.USER_PREF_KEY )) );

MqttHelper().send('hi from the app', user.mqttClientId);
MSource of the question:
https://stackoverflow.com/questions/79031816

Question and source license information:
https://meta.stackexchange.com/help/licensing
https://stackoverflow.com/

Видео How can I keep a variable value inside an isolate/FlutterBackgroundService? канала Emrah KAYA