新 전체코드

var token;

Future<void> getToken() async {
  FirebaseMessaging messaging = FirebaseMessaging.instance;
  await messaging.requestPermission();
  token = await messaging.getToken();
  print('토큰 : $token');
}

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);
  getToken();
  LocalNotification.initialize();
  runApp(const MyApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});
  final String title;
  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  void initState() {
    FirebaseMessaging.onMessage.listen((RemoteMessage message) {
      showNotification(message);
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    LocalNotification.requestPermission();

    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            TextButton(
              child: const Text('알림 띄우기'),
              onPressed: () {
                print('temp');
              },
            ),
          ],
        ),
      ),
    );
  }
}

import 'package:flutter_local_notifications/flutter_local_notifications.dart';

class LocalNotification {
  LocalNotification._();

  static FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
      FlutterLocalNotificationsPlugin();

  static initialize() async {
    AndroidInitializationSettings initializationSettingsAndroid =
        const AndroidInitializationSettings('favicon');

    DarwinInitializationSettings initializationSettingsIos =
        const DarwinInitializationSettings(
            requestAlertPermission: true,
            requestBadgePermission: true,
            requestSoundPermission: true);
    InitializationSettings initializationSettings = InitializationSettings(
      android: initializationSettingsAndroid,
      iOS: initializationSettingsIos,
    );
    await flutterLocalNotificationsPlugin.initialize(initializationSettings);
  }

  static void requestPermission() {
    flutterLocalNotificationsPlugin
        .resolvePlatformSpecificImplementation<
            IOSFlutterLocalNotificationsPlugin>()
        ?.requestPermissions(alert: true, badge: true, sound: true);
  }
}

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

final notifications = FlutterLocalNotificationsPlugin();

showNotification(RemoteMessage message) async {
  var androidDetails = const AndroidNotificationDetails(
    '유니크한 알림 채널 ID',
    '알림종류 설명',
    priority: Priority.high,
    importance: Importance.max,
    color: Color.fromARGB(255, 255, 0, 0),
  );

  var iosDetails = const DarwinNotificationDetails(
    presentAlert: true,
    presentBadge: true,
    presentSound: true,
    badgeNumber: 9999,
  );

  RemoteNotification? notification = message.notification;

  // 알림 id, 제목, 내용 맘대로 채우기
  notifications.show(
    notification.hashCode,
    notification!.title,
    notification.body,
    NotificationDetails(android: androidDetails, iOS: iosDetails),
  );
}

舊 전체코드

@pragma('vm:entry-point')
// 백그라운드 핸들러
Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
  await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);
  await setupFlutterNotifications(); // firebase 세팅 아래에 설명
  showFlutterNotification(message); // 메시지 보이기 아래에 설명
}

var isFlutterLocalNotificationsInitialized = false;
var flutterLocalNotificationsPlugin;
var channel;
var initalizationsSetting;
var initalizationsSettingsIos;
var initalizationSettingsAndroid;
String? token;


Future<void> setupFlutterNotifications() async {
  if (isFlutterLocalNotificationsInitialized) {
    return;
  }
  channel = const AndroidNotificationChannel(
    'high_importance_channel', // id는 AndroidManifest.xml 파일에서 설정한 default_notification_channel_id 값과 같아야한다
    'High Importance Notifications', // title
    description:
        'This channel is used for important notifications.', // description
    importance: Importance.high,
  );

  flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();
  await flutterLocalNotificationsPlugin
      .resolvePlatformSpecificImplementation<
          AndroidFlutterLocalNotificationsPlugin>()
      ?.requestPermissions(alert: true, badge: true, sound: true);

  initalizationSettingsAndroid = AndroidInitializationSettings('defaultIcon');
  initalizationsSettingsIos = DarwinInitializationSettings();
  initalizationsSetting = InitializationSettings(
      android: initalizationSettingsAndroid, iOS: initalizationsSettingsIos);
  flutterLocalNotificationsPlugin.initialize(initalizationsSetting,
      onDidReceiveNotificationResponse:
          (NotificationResponse notificationResponse) async {
    debugPrint('notificationResponse: $notificationResponse');
  });

  // iOS foreground notification 권한
  await FirebaseMessaging.instance.setForegroundNotificationPresentationOptions(
    alert: true,
    badge: true,
    sound: true,
  );
  // IOS background 권한 체킹 , 요청
  await FirebaseMessaging.instance.requestPermission(
    alert: true,
    announcement: false,
    badge: true,
    carPlay: false,
    criticalAlert: false,
    provisional: false,
    sound: true,
  );
  getTokenMth();
  isFlutterLocalNotificationsInitialized = true;
}


Future<void> getTokenMth() async {
  final fcm = FirebaseMessaging.instance;
  await fcm.requestPermission();
  token = await fcm.getToken();
}


void showFlutterNotification(RemoteMessage message) {
  print("message : ===== ${message.toString()}");
  RemoteNotification? notification = message.notification;
  AndroidNotification? android = message.notification?.android;
  if (notification != null && android != null && !kIsWeb) {
    flutterLocalNotificationsPlugin.show(
      notification.hashCode,
      notification.title,
      notification.body,
      NotificationDetails(
        android: AndroidNotificationDetails(
          channel.id,
          channel.name,
          channelDescription: channel.description,
          icon: 'launch_background',
        ),
      ),
    );
  }
  AppleNotification? apple = message.notification?.apple;
  if (notification != null && apple != null && !kIsWeb) {
    flutterLocalNotificationsPlugin.show(
      notification.hashCode,
      notification.title,
      notification.body,
      const NotificationDetails(iOS: DarwinNotificationDetails()),
    );
  }
}


void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  if (Firebase.apps.isEmpty) {
    await Firebase.initializeApp(
        options: DefaultFirebaseOptions.currentPlatform);
  } else {
    Firebase.app();
  }

  FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);

  if (!kIsWeb) {
    await setupFlutterNotifications();
  }
  runApp(const MyApp());
}

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

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

class _AppState extends State<MyApp> {
  void setupPushNotifications() async {
    final fcm = FirebaseMessaging.instance;
    await fcm.requestPermission();
    token = await fcm.getToken();
  }

  @override
  void initState() {
    super.initState();
    FirebaseMessaging.onMessage.listen(showFlutterNotification);
    FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);
    FirebaseMessaging.onMessageOpenedApp.listen((event) {
      print('event: $event');
    });
    // setupPushNotifications();
  }

  GoRouter get _router => GoRouter(
        initialLocation: '/',
        routes: [
          GoRoute(
            path: '/',
            builder: (_, state) => WebViewVue(
              token: token,
            ),
          ),
        ],
      );

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routerConfig: _router,
      theme: ThemeData(fontFamily: 'NotoSans'),
      debugShowCheckedModeBanner: false,
    );
  }
}