Autenticação com Flutter e Firebase: Guia de Login com Email e Senha

import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';

// Tela de Login
class LoginPage extends StatefulWidget {
  const LoginPage({super.key});

  @override
  State<LoginPage> createState() => _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {
  final TextEditingController _emailController = TextEditingController();
  final TextEditingController _passwordController = TextEditingController();
  bool _isLoading = false;

  // Função para lidar com o processo de login
  Future<void> _login() async {
    setState(() {
      _isLoading = true;
    });

    try {
      // Tenta fazer login com email e senha
      await FirebaseAuth.instance.signInWithEmailAndPassword(
        email: _emailController.text.trim(),
        password: _passwordController.text.trim(),
      );
      // Se o login for bem-sucedido, o StreamBuilder no AuthWrapper
      // irá reconstruir e levar o usuário para a HomePage.
    } on FirebaseAuthException catch (e) {
      // Mostra um erro para o usuário se o login falhar
      final snackBar = SnackBar(
        content: Text('Erro ao fazer login: ${e.message}'),
        backgroundColor: Colors.red,
      );
      ScaffoldMessenger.of(context).showSnackBar(snackBar);
    } finally {
      // Garante que o estado de loading seja desativado
      if (mounted) {
        setState(() {
          _isLoading = false;
        });
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Login')),
      body: Center(
        child: SingleChildScrollView(
          padding: const EdgeInsets.all(16.0),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              const Icon(Icons.lock, size: 80, color: Colors.blue),
              const SizedBox(height: 20),
              TextField(
                controller: _emailController,
                decoration: const InputDecoration(
                  labelText: 'Email',
                  border: OutlineInputBorder(),
                  prefixIcon: Icon(Icons.email),
                ),
                keyboardType: TextInputType.emailAddress,
              ),
              const SizedBox(height: 16),
              TextField(
                controller: _passwordController,
                decoration: const InputDecoration(
                  labelText: 'Senha',
                  border: OutlineInputBorder(),
                  prefixIcon: Icon(Icons.vpn_key),
                ),
                obscureText: true,
              ),
              const SizedBox(height: 24),
              // Mostra o botão ou o loader
              _isLoading
                  ? const CircularProgressIndicator()
                  : ElevatedButton(
                      onPressed: _login,
                      style: ElevatedButton.styleFrom(
                        padding: const EdgeInsets.symmetric(
                          horizontal: 50,
                          vertical: 15,
                        ),
                      ),
                      child: const Text('Entrar'),
                    ),
            ],
          ),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';

// Tela Home, exibida após o login
class HomePage extends StatelessWidget {
  final User user;

  const HomePage({super.key, required this.user});

  // Função para fazer logout
  Future<void> _logout() async {
    await FirebaseAuth.instance.signOut();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Página Inicial'),
        actions: [
          IconButton(
            icon: const Icon(Icons.logout),
            onPressed: _logout,
          ),
        ],
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text(
              'Bem-vindo!',
              style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
            ),
            const SizedBox(height: 16),
            Text(
              user.email ?? 'Email não disponível',
              style: const TextStyle(fontSize: 18),
            ),
          ],
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'firebase_options.dart'; // Importa as configurações
import 'pages/home_page.dart'; // Importa a HomePage
import 'pages/login_page.dart'; // Importa a LoginPage

// Ponto de entrada da aplicação
void main() async {
  // Garante que os widgets do Flutter estão prontos
  WidgetsFlutterBinding.ensureInitialized();
  // Inicializa o Firebase
  await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);
  runApp(const MyApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Firebase Auth',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      // O AuthWrapper decide qual tela mostrar
      home: const AuthWrapper(),
      debugShowCheckedModeBanner: false,
    );
  }
}

// O AuthWrapper ouve as mudanças de estado de autenticação
class AuthWrapper extends StatelessWidget {
  const AuthWrapper({super.key});

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<User?>(
      // Ouve o stream de estado de autenticação do Firebase
      stream: FirebaseAuth.instance.authStateChanges(),
      builder: (context, snapshot) {
        // Enquanto está conectando, mostra um loader
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const Scaffold(
            body: Center(child: CircularProgressIndicator()),
          );
        }
        // Se o snapshot tem dados, significa que o usuário está logado
        if (snapshot.hasData) {
          return HomePage(user: snapshot.data!);
        }
        // Se não tem dados, mostra a tela de login
        return const LoginPage();
      },
    );
  }
}