Flutter – await Firebase.InitializeApp() do not working

Add these dependencies in your pubspec.yaml file

  firebase_core: ^2.21.0

then inside main.dart file

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

if you are setting firebase for push notifications add these 2 also in pubspec.yaml

  firebase_messaging: ^14.7.3
  flutter_local_notifications: ^16.1.0

Then finally, Install FlutterFire CLI from https://firebase.google.com/docs/cli#setup_update_cli

then open terminal and use command below and follow instruction

flutterfire configure

this will generate firebase_options.dart file.

Also to implement push notifications you can add this code (create new file firebase_api.dart)

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

final _localNotifications = FlutterLocalNotificationsPlugin();

//this function is used for handleing background notifications for Android,
Future<void> handleBackgroudMessage(RemoteMessage message) async {
  print('Title: ${message.notification?.title}');
  print('Body: ${message.notification?.body}');
  print('PayLoad: ${message.data}');
}

final androidchannel = const AndroidNotificationChannel(
    'high_importance_channel', 'High Importance Notifications',
    description: 'This channel is used for important notification ',
    importance: Importance.defaultImportance);
// Function for Sending to selected page from notifications
void handleMessage(RemoteMessage? message) {
  if (message == null) {
    return;
  }
}

Future initLocalNotification() async {
  const android = AndroidInitializationSettings('@drawable/ic_launcher');
  const iOS = DarwinInitializationSettings();
  const settings = InitializationSettings(android: android, iOS: iOS);
  await _localNotifications.initialize(settings,
      onDidReceiveNotificationResponse: (payload) {
    final message = RemoteMessage.fromMap(jsonDecode(payload as String));
    handleMessage(message);
  });
  final platform = _localNotifications.resolvePlatformSpecificImplementation<
      AndroidFlutterLocalNotificationsPlugin>();
  await platform?.createNotificationChannel(androidchannel);
}

Future initNotifications() async {
  await FirebaseMessaging.instance.setForegroundNotificationPresentationOptions(
      alert: true, badge: true, sound: true);

  FirebaseMessaging.instance.getInitialMessage().then(handleMessage);
  FirebaseMessaging.onMessageOpenedApp.listen(handleMessage);
  FirebaseMessaging.onBackgroundMessage(handleBackgroudMessage);
  FirebaseMessaging.onMessage.listen((message) {
    final notification = message.notification;
    if (notification == null) {
      return;
    }

    _localNotifications.show(
      notification.hashCode,
      notification.title,
      notification.body,
      NotificationDetails(
        android: AndroidNotificationDetails(
          androidchannel.id,
          androidchannel.name,
          channelDescription: androidchannel.description,
        ),
      ),
      payload: jsonEncode(message.toMap()),
    );
  });
}

//function for firebase and asking for persmission of notifications,
void setupPushNotifications() async {
  final fcm = FirebaseMessaging.instance;

  await fcm.requestPermission();
  final token = await fcm.getToken();
  print("Token : $token");

  fcm.subscribeToTopic("ALL");

  FirebaseMessaging.onBackgroundMessage(handleBackgroudMessage);
  initNotifications();
  initLocalNotification();
}

and in main.dart file
make you widget stateful (if not) and then use init method for using this code,

 @override
  void initState() {
    // initializing push notifications service (ask for permissions)
    setupPushNotifications();
    super.initState();
  }