Auth Service
Create a file named auth.dart in the services directory.
services/auth.dart
import 'package:firebase_auth/firebase_auth.dart';
class AuthService {
final userStream = FirebaseAuth.instance.authStateChanges();
final user = FirebaseAuth.instance.currentUser;
}
Listen to Current User
Use the home page to render a different set of UI elements based on the user’s auth state in Firebase. If the user is signed in, show the topics screen. If the user is not signed in, show the login screen.
home.dart
import 'package:flutter/material.dart';
import 'package:quizapp/login/login.dart';
import 'package:quizapp/shared/shared.dart';
import 'package:quizapp/topics/topics.dart';
import 'package:quizapp/services/auth.dart';
class HomeScreen extends StatelessWidget {
const HomeScreen({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return StreamBuilder(
stream: AuthService().userStream,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return const LoadingScreen();
} else if (snapshot.hasError) {
return const Center(
child: ErrorMessage(),
);
} else if (snapshot.hasData) {
return const TopicsScreen();
} else {
return const LoginScreen();
}
},
);
}
}
Login Screen
Update the login screen with a Scaffold.
main.dart
class LoginScreen extends StatelessWidget {
const LoginScreen({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Login'),
),
);
}
}