Initialize Firebase in Your Flutter App

Update Your Main Dart File: you initialize Firebase before using any Firebase services:

import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
 void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}
class MyApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
   return MaterialApp(
     title: 'Flutter Firebase Demo',
       home: Scaffold(
       appBar: AppBar(
       title: Text('Flutter Firebase Demo'),
      ),
      body: Center(
       child: Text('Hello, Firebase!'),
      ),
   ),
  );
 }
}