something

android/app/build.gradle

@@ -64,4 +64,13 @@ flutter {
     source '../..'
 }
 
-dependencies {}
+dependencies {
+    constraints {
+        implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk7:1.8.0") {
+            because("kotlin-stdlib-jdk7 is now a part of kotlin-stdlib")
+        }
+        implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.8.0") {
+            because("kotlin-stdlib-jdk8 is now a part of kotlin-stdlib")
+        }
+    }
+}

lib/main.dart

@@ -1,6 +1,7 @@
 import 'package:dynamic_color/dynamic_color.dart';
 import 'package:flutter/material.dart';
 import 'package:hrt/notification.dart';
+import 'package:hrt/tasks.dart';
 import 'package:permission_handler/permission_handler.dart';
 
 void main() {
@@ -12,6 +13,7 @@ class App extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    setupBackgroundTasks();
     return DynamicColorBuilder(
       builder: ((lightDynamic, darkDynamic) => MaterialApp(
           title: "HRT",

lib/tasks.dart

@@ -0,0 +1,58 @@
+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') {
+      sendNotification();
+    }
+
+    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'),
+    ),
+    // onSelectNotification: handleNotificationClick,
+  );
+
+  var launchDetails =
+      await FlutterLocalNotificationsPlugin().getNotificationAppLaunchDetails();
+
+  // if (launchDetails?.payload != null && launchDetails!.payload!.isNotEmpty) {
+  //   handleNotificationClick(launchDetails.payload);
+  // }
+
+  // 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),
+  );
+}

pubspec.lock

@@ -106,10 +106,10 @@ packages:
     dependency: "direct main"
     description:
       name: flutter_local_notifications
-      sha256: "3002092e5b8ce2f86c3361422e52e6db6776c23ee21e0b2f71b892bf4259ef04"
+      sha256: "501ed9d54f1c8c0535b7991bade36f9e7e3b45a2346401f03775c1ec7a3c06ae"
       url: "https://pub.dev"
     source: hosted
-    version: "15.1.1"
+    version: "15.1.2"
   flutter_local_notifications_linux:
     dependency: transitive
     description:
@@ -281,7 +281,7 @@ packages:
     source: hosted
     version: "0.6.1"
   timezone:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: timezone
       sha256: "1cfd8ddc2d1cfd836bc93e67b9be88c3adaeca6f40a00ca999104c30693cdca0"
@@ -304,6 +304,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.1.4-beta"
+  workmanager:
+    dependency: "direct main"
+    description:
+      name: workmanager
+      sha256: ed13530cccd28c5c9959ad42d657cd0666274ca74c56dea0ca183ddd527d3a00
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.5.2"
   xdg_directories:
     dependency: transitive
     description:

pubspec.yaml

@@ -38,6 +38,8 @@ dependencies:
   dynamic_color: ^1.6.7
   flutter_local_notifications: ^15.1.1
   permission_handler: ^11.0.1
+  workmanager: ^0.5.2
+  timezone: ^0.9.2
 
 dev_dependencies:
   flutter_test: