Display Local Notifications on Flutter the moment the App goes to the background

Question

For some weird reasons I can't get notifications displayed on my flutter app the moment the app is exited.

What I want is that the moment the user exists the app I want to display a notification to tell the user that the app has currently gone into the background.

I am currently using the flutter_local_notifications plugin to achieve this but it isn't working.

Here is what I have tried:

class HomePage extends StatefulWidget {
  static const routePath = "/home";

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage > with WidgetsBindingObserver {

  @override
  initState() {
    WidgetsBinding.instance!.addObserver(this);
    super.initState();
  }

  @override
  void dispose() {
    WidgetsBinding.instance!.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);
    bool inBackground = state == AppLifecycleState.paused;
    if (inBackground) {
displayNotification("AppName","App has gone into the background",null); //This is not displaying at all when the app goes into the background. It only displays when the app is in the foreground. I want it to display the moment the user exits the app.
    }
  }

Future<void> displayNotification(
  String title,
  String description,
  dynamic payload, {
  bool ongoing = false,
}) async {
.....

Any insights to get around this would be really appreciated.

Answer 1

I test this and worked for me

main.dart :

import 'package:flutter/material.dart';
import 'package:local_notification/local_notification.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> with WidgetsBindingObserver {
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance?.addObserver(this);
  }

  @override
  void dispose() {
    WidgetsBinding.instance?.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);
    var appInBackground = (state == AppLifecycleState.inactive);
    if (appInBackground)
      showNotificationMessage('App has gone into the background', 'FlutterApp');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Text(
          'Testing app local notification\r\n'
          ' in background mode!',
          style: TextStyle(fontSize: 28),
        ),
      ),
    );
  }
}

local_notification.dart :

import 'package:flutter_local_notifications/flutter_local_notifications.dart';

//define this method in global scope not a class scope
void showNotificationMessage(String? description, String? title) {
  FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin;
  flutterLocalNotificationsPlugin = new FlutterLocalNotificationsPlugin();
  var android = new AndroidInitializationSettings('@mipmap/ic_launcher');
  var iOS = new IOSInitializationSettings();
  var initSettings = new InitializationSettings(android: android, iOS: iOS);
  flutterLocalNotificationsPlugin.initialize(initSettings,
      onSelectNotification: null);

  String groupKey = 'com.example.general-notification-channel';
  var androidPlatformChannelSpecifics = new AndroidNotificationDetails(
    'general-notification-channel',
    'general-notification-channel',
    'general-notification-channel',
    importance: Importance.max,
    priority: Priority.high,
    groupKey: groupKey,
    //   setAsGroupSummary: true
  );

  var iOSPlatformChannelSpecifics = new IOSNotificationDetails();
  NotificationDetails platformChannelSpecifics = new NotificationDetails(
      android: androidPlatformChannelSpecifics,
      iOS: iOSPlatformChannelSpecifics);
  flutterLocalNotificationsPlugin.show(
      0, title, description, platformChannelSpecifics);
}

pubspec.yaml :

name: local_notification
description: A new Flutter project.
publish_to: 'none'
version: 1.0.0+1

environment:
  sdk: ">=2.12.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^1.0.3
  flutter_local_notifications: ^6.0.0

dev_dependencies:
  flutter_test:
    sdk: flutter


flutter:
  uses-material-design: true