Short boilerplate for setting up flutter local notification package

flutter_local_notification.dart

import 'dart:async';
import 'dart:convert';
import 'dart:math';

import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';

import '../utils/logger/logger.dart';

const _channelId = '<your_channel_id>';
const _channelDeception = '<your_channel_desc>';
const _channelTitle = '<your_channel_title>';
const _topicKey = 'general';

class NotificationService {
  factory NotificationService() {
    return _instance ??= NotificationService._();
  }

  NotificationService._();
  static NotificationService? _instance;

  final _firebaseMessaging = FirebaseMessaging.instance;

  final _flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();

  var _didInitializeNotificationService = false;
  Future<void> initialize() async {
    if (_didInitializeNotificationService) {
      Logger.w('You already initialized the notification service. '
          'Ignoring the reinitialize request!');
      return;
    }

    final settings = await _firebaseMessaging.requestPermission();

    if (settings.authorizationStatus != AuthorizationStatus.authorized) {
      return;
    }

    unawaited(_firebaseMessaging.subscribeToTopic(_topicKey));

    await _initLocalNotificationPackage();

    _startNotificationsListener();

    _didInitializeNotificationService = true;
  }

  Future<void> _initLocalNotificationPackage() async {
    await _flutterLocalNotificationsPlugin
        .resolvePlatformSpecificImplementation<
            AndroidFlutterLocalNotificationsPlugin>()
        ?.createNotificationChannel(
          const AndroidNotificationChannel(
            _channelId,
            _channelTitle,
            description: _channelDeception,
            importance: Importance.max,
            enableLights: true,
          ),
        );

    const initializationSettingsAndroid =
        AndroidInitializationSettings('@mipmap/ic_stat_notification_icon');

    const darwinInitializationSettings = DarwinInitializationSettings();

    const initializationSettings = InitializationSettings(
      android: initializationSettingsAndroid,
      iOS: darwinInitializationSettings,
    );

    await _flutterLocalNotificationsPlugin.initialize(
      initializationSettings,
      onDidReceiveNotificationResponse: (details) {
        if (details.payload != null) {
          _handleNotificationTap(
            json.decode(details.payload!) as Map<String, dynamic>,
          );
        }
      },
    );
  }

  bool _isNotificationListenerInitialized = false;

  void _startNotificationsListener() {
    if (_isNotificationListenerInitialized) {
      Logger.w('You already started the notification Listener. '
          'Ignoring the start request!');
      return;
    }
    _isNotificationListenerInitialized = true;

    // show notifications
    FirebaseMessaging.onMessage.listen(_showNotification);
  }

  bool _isTapListenersInitialized = false;

  Future<void> startTapNotificationsListener() async {
    assert(
      _didInitializeNotificationService,
      'Did you forget to initialize the notification service?',
    );

    if (_isTapListenersInitialized) {
      return;
    }
    _isTapListenersInitialized = true;

    // handle notification tap

    final remoteInitialMessage =
        await FirebaseMessaging.instance.getInitialMessage();
    if (remoteInitialMessage != null) {
      _handleNotificationTap(remoteInitialMessage.data);
    }

    FirebaseMessaging.onMessageOpenedApp.listen((remoteMessage) {
      _handleNotificationTap(remoteMessage.data);
    });

    final notificationAppLaunchDetails = await _flutterLocalNotificationsPlugin
        .getNotificationAppLaunchDetails();

    if (notificationAppLaunchDetails != null) {
      final payload =
          notificationAppLaunchDetails.notificationResponse?.payload;
      if (payload != null) {
        _handleNotificationTap(json.decode(payload) as Map<String, dynamic>);
      }
    }
  }

  Future<void> _showNotification(RemoteMessage message) async {
    final bigTextStyleInformation = BigTextStyleInformation(
      message.notification?.body.toString() ?? '',
      contentTitle: message.notification?.title.toString(),
    );

    final androidPlatformChannelSpecifics = AndroidNotificationDetails(
      _channelId,
      _channelTitle,
      channelDescription: _channelDeception,
      importance: Importance.max,
      styleInformation: bigTextStyleInformation,
      priority: Priority.max,
    );

    final platformChannelSpecifics =
        NotificationDetails(android: androidPlatformChannelSpecifics);

    await _flutterLocalNotificationsPlugin.show(
      Random().nextInt(99999),
      message.notification?.title,
      message.notification?.body,
      platformChannelSpecifics,
      payload: json.encode(message.data),
    );
  }
}

void _handleNotificationTap(Map<String, dynamic> payload) {
  // handel notification tap
}