hrt/lib/tasks.dart

import 'package:flutter/foundation.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:hrt/notification.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:workmanager/workmanager.dart';

@pragma('vm:entry-point')
void callbackDispatcher() {
  Workmanager().executeTask((taskName, inputData) async {
    print("Native called background task: $taskName");

    if (taskName == 'scheduleNotifications') {
      scheduleNotification();
    }

    return true;
  });
}

void setupBackgroundTasks() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Workmanager().initialize(
    callbackDispatcher,
    isInDebugMode: kDebugMode,
  );

  await Permission.notification.request();

  await FlutterLocalNotificationsPlugin().initialize(
    const InitializationSettings(
      android: AndroidInitializationSettings('estrogen'),
    ),
  );

  // Runs every 15 minutes
  await Workmanager().registerPeriodicTask(
    'schedule_notifications',
    'scheduleNotifications',
    constraints: Constraints(
      networkType: NetworkType.not_required,
      requiresCharging: false,
      requiresBatteryNotLow: false,
      requiresDeviceIdle: false,
      requiresStorageNotLow: false,
    ),
    initialDelay: const Duration(seconds: 15),
    frequency: const Duration(minutes: 15),
  );
}