ChatApp in Flutter

Below is a complete example of a simple Flutter chat app using Firebase Firestore for real-time messaging and Firebase Authentication for user login/signup. This example includes the UI, backend integration, and basic functionality.

Full Code for Flutter Chat App

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1: Add the required dependencies: pubspec.yaml

  firebase_core: latest_version 
  firebase_auth: latest_version 
  cloud_firestore: latest_version
  provider: latest_version

Run flutter pub get to install the dependencies.

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2: Set up Firebase and the main app structure: main.dart

import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:foodiesapp/new/auth_service.dart';
import 'package:foodiesapp/new/chat_screen.dart';
import 'package:foodiesapp/new/login_screen.dart';
import 'package:provider/provider.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(const MyApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        Provider<AuthService>(
          create: (_) => AuthService(),
        ),
      ],
      child: MaterialApp(
        title: 'Chat App',
        debugShowCheckedModeBanner: false,
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: const AuthWrapper(),
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    final authService = Provider.of<AuthService>(context);
    return StreamBuilder<User?>(
      stream: authService.user,
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.active) {
          final user = snapshot.data;
          return user == null ? LoginScreen() : ChatScreen();
        } else {
          return const Scaffold(
            body: Center(
              child: CircularProgressIndicator(),
            ),
          );
        }
      },
    );
  }
}

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3: Handle user authentication:auth_service.dart

import 'package:firebase_auth/firebase_auth.dart';

class AuthService {
  final FirebaseAuth _auth = FirebaseAuth.instance;

  // Stream to listen to auth state changes
  Stream<User?> get user {
    return _auth.authStateChanges();
  }

  // Sign in with email and password
  Future<void> signIn(String email, String password) async {
    try {
      await _auth.signInWithEmailAndPassword(email: email, password: password);
    } catch (e) {
      print('Error signing in: $e');
    }
  }

  // Sign up with email and password
  Future<void> signUp(String email, String password) async {
    try {
      await _auth.createUserWithEmailAndPassword(email: email, password: password);
    } catch (e) {
      print('Error signing up: $e');
    }
  }

  // Sign out
  Future<void> signOut() async {
    await _auth.signOut();
  }
}

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4: Create a login/signup screen: login_screen.dart

import 'package:flutter/material.dart';
import 'auth_service.dart';
import 'package:provider/provider.dart';

class LoginScreen extends StatelessWidget {
  final TextEditingController _emailController = TextEditingController();
  final TextEditingController _passwordController = TextEditingController();

  LoginScreen({super.key});

  @override
  Widget build(BuildContext context) {
    final authService = Provider.of<AuthService>(context);

    return Scaffold(
      appBar: AppBar(
        title: const Text('Login / Signup'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            TextField(
              controller: _emailController,
              decoration: const InputDecoration(labelText: 'Email'),
            ),
            TextField(
              controller: _passwordController,
              decoration: const InputDecoration(labelText: 'Password'),
              obscureText: true,
            ),
            const SizedBox(height: 20),
            ElevatedButton(
              onPressed: () async {
                await authService.signIn(
                  _emailController.text,
                  _passwordController.text,
                );
              },
              child: const Text('Login'),
            ),
            ElevatedButton(
              onPressed: () async {
                await authService.signUp(
                  _emailController.text,
                  _passwordController.text,
                );
              },
              child: const Text('Signup'),
            ),
          ],
        ),
      ),
    );
  }
}

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5: Create the chat screen with real-time messaging: chat_screen.dart

import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'auth_service.dart';
import 'package:provider/provider.dart';

class ChatScreen extends StatelessWidget {
  final TextEditingController _messageController = TextEditingController();
  final FirebaseFirestore _firestore = FirebaseFirestore.instance;

  ChatScreen({super.key});

  @override
  Widget build(BuildContext context) {
    final authService = Provider.of<AuthService>(context);
    final userStream = authService.user;

    return Scaffold(
      appBar: AppBar(
        title: const Text('Chat App'),
        actions: [
          IconButton(
            icon: const Icon(Icons.logout),
            onPressed: () async {
              await authService.signOut();
            },
          ),
        ],
      ),
      body: Column(
        children: [
          Expanded(
            child: StreamBuilder<QuerySnapshot>(
              stream: _firestore
                  .collection('messages')
                  .orderBy('timestamp', descending: false)
                  .snapshots(),
              builder: (context, snapshot) {
                if (!snapshot.hasData) {
                  return const Center(
                    child: CircularProgressIndicator(),
                  );
                }

                final messages = snapshot.data!.docs;
                List<Widget> messageWidgets = [];
                for (var message in messages) {
                  final messageText = message['text'];
                  final messageSender = message['sender'];

                  final messageWidget = ListTile(
                    title: Text(messageText),
                    subtitle: Text(messageSender),
                  );
                  messageWidgets.add(messageWidget);
                }

                return ListView(
                  children: messageWidgets,
                );
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: Row(
              children: [
                Expanded(
                  child: TextField(
                    controller: _messageController,
                    decoration: const InputDecoration(
                      hintText: 'Enter your message...',
                    ),
                  ),
                ),
                StreamBuilder<User?>(
                  stream: userStream,
                  builder: (context, snapshot) {
                    if (!snapshot.hasData) {
                      return const IconButton(
                        icon: Icon(Icons.send),
                        onPressed: null,
                      );
                    }
                    final user = snapshot.data;
                    return IconButton(
                      icon: const Icon(Icons.send),
                      onPressed: () async {
                        if (_messageController.text.isNotEmpty) {
                          await _firestore.collection('messages').add({
                            'text': _messageController.text,
                            'sender': user!.email,
                            'timestamp': FieldValue.serverTimestamp(),
                          });
                          _messageController.clear();
                        }
                      },
                    );
                  },
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }
}

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