I’m using the Flutter local notification package in my expiry reminder app. However, notifications about product expirations are inconsistent. Sometimes the notifications are delivered as expected, but most of the time, users do not receive them.

I want the functionality to be like alarm apps: when a user sets an expiration time for a product, they should reliably receive a notification at that time.

My main file code

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await MyDatabase().copyPasteAssetFileToRoot();
  await MyDatabase().updateDayLeftForAllProducts();
  // await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);
  await NotificationHelper.init();
  tz.initializeTimeZones();
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    _requestNotificationPermission();
  }

  Future<void> _requestNotificationPermission() async {
    var status = await Permission.notification.status;
    if (status.isDenied || status.isPermanentlyDenied) {
      status = await Permission.notification.request();
      if (status.isGranted) {
        print("Notification permission granted.");
      } else {
        print("Notification permission denied.");
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return MultiProvider(
        providers: [
          ChangeNotifierProvider(create: (_) => AddItemsProvider()),
          ChangeNotifierProvider(create: (_) => CategoryProvider()),
        ],
        child: Sizer(builder: (context, orientation, screenType) {
          return MaterialApp(
            navigatorKey: navigatorKey,
            debugShowCheckedModeBanner: false,
            title: "Expiry Reminder",
            home: SplashPage(),
          );
        }));
  }
}

These is my Notification file code which is not working proper according to the requirement

import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:timezone/timezone.dart' as tz;

class NotificationHelper {
  static final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
      FlutterLocalNotificationsPlugin();

  static Future<void> onDidReceiveBackgroundNotification(
      NotificationResponse notificationResponse) async {}

  static Future<void> init() async {
    const AndroidInitializationSettings androidInitializationSettings =
        AndroidInitializationSettings('@drawable/launcher_icon');
    const DarwinInitializationSettings iOSInitializationSettings =
        DarwinInitializationSettings();

    const InitializationSettings initializationSettings =
        InitializationSettings(
            android: androidInitializationSettings,
            iOS: iOSInitializationSettings);

    await flutterLocalNotificationsPlugin.initialize(
      initializationSettings,
      onDidReceiveBackgroundNotificationResponse:
          onDidReceiveBackgroundNotification,
      onDidReceiveNotificationResponse: onDidReceiveBackgroundNotification,
    );

    await flutterLocalNotificationsPlugin
        .resolvePlatformSpecificImplementation<
            AndroidFlutterLocalNotificationsPlugin>()
        ?.requestExactAlarmsPermission();
  }

  static Future<void> scheduleReminderNotifications({
    required String productName,
    required DateTime reminderDate,
    required String reminderTime,
    required String operation,
    required int id,
  }) async {
    List<String> timeParts = reminderTime.split(":");
    final scheduledDate = DateTime(
      reminderDate.year,
      reminderDate.month,
      reminderDate.day,
      int.parse(timeParts[0]),
      int.parse(timeParts[1]),
    );

    if (scheduledDate.isBefore(DateTime.now())) {
      print("Scheduled date must be in the future.");
      return;
    }

    print("Scheduling notification for: $reminderDate for id: $id");

    if (operation == "update") {
      print("Cancel existing notification for id $id");
      await cancelNotification(id);
    }

    await _scheduleNotification(
      id: id,
      title:
          'Attention: ${productName[0].toUpperCase() + productName.substring(1)} Expiration Alert',
      body:
          'Heads up! Your $productName will expire on ${scheduledDate.toString().split(" ")[0]}.',
      scheduledDate: scheduledDate,
    );
  }

  static Future<void> cancelNotification(int id) async {
    await flutterLocalNotificationsPlugin.cancel(id);
  }

  static Future<void> _scheduleNotification({
    required int id,
    required String title,
    required String body,
    required DateTime scheduledDate,
  }) async {
    const NotificationDetails platformChannelSpecifics = NotificationDetails(
      android: AndroidNotificationDetails(
        "channelId",
        "channelName",
        importance: Importance.high,
        priority: Priority.high,
      ),
      iOS: DarwinNotificationDetails(),
    );

    await flutterLocalNotificationsPlugin.zonedSchedule(
      id,
      title,
      body,
      tz.TZDateTime.from(scheduledDate, tz.local),
      platformChannelSpecifics,
      uiLocalNotificationDateInterpretation:
          UILocalNotificationDateInterpretation.absoluteTime,
      androidScheduleMode: AndroidScheduleMode.exactAllowWhileIdle,
      matchDateTimeComponents: DateTimeComponents.dateAndTime,
    );
  }
}

these is how i am adding the notifications

if (buttonText == "Add") {
 if (reminderDate.text.isNotEmpty) {
     NotificationHelper
    .scheduleReminderNotifications(
   productName: productName.text,
  reminderDate: DateTime.parse(
  reminderDate.text),
  reminderTime:
  reminderTimeValue.text,
  operation: buttonText,
  id: index,
 );
} 

//for update purpose
if (reminderDate.text.isNotEmpty) {
                                            NotificationHelper
                                                .scheduleReminderNotifications(
                                              productName: productName.text,
                                              reminderDate: DateTime.parse(
                                                  reminderDate.text),
                                              reminderTime:
                                                  reminderTimeValue.text,
                                              operation: "update",
                                              id: index,
                                            );
                                          }                                        

Please Solve the issue related to the notifications