Flutter Login App with Google Sign-In

A Flutter application demonstrating Google Sign-In integration with JWT token authentication.

Features

• Google Sign-In Authentication
• JWT Token Management
• Persistent Authentication State
• Material Design UI
• Secure Token Storage

Setup Instructions

1. Flutter Setup

   flutter pub get

2. Google Sign-In Configuration

   a. Go to the Google Cloud Console

   b. Create a new project or select an existing one

   c. Enable the Google Sign-In API

   d. Create OAuth 2.0 credentials:

   • Create OAuth client ID
   • Select "Web application" as the application type
   • Add authorized redirect URIs
   • Download the client configuration file

3. Backend Configuration

   Update the _apiUrl in lib/services/auth_service.dart with your backend API URL:

   static const String _apiUrl = 'YOUR_API_URL';

4. Running the App

   flutter run

Project Structure

lib/
├── main.dart              # App entry point and navigation setup
├── screens/
│   └── login_screen.dart  # Login page UI
└── services/
    └── auth_service.dart  # Authentication logic

Authentication Flow

1. User clicks "Sign in with Google" button
2. Google Sign-In flow is initiated
3. After successful Google authentication:
   • Backend receives Google token
   • Backend validates token and creates JWT
   • App stores JWT for future requests
4. User is redirected to home screen
5. JWT is used for subsequent API requests

Security Considerations

• JWT tokens are stored securely using SharedPreferences
• HTTPS is used for all API communications
• Google Sign-In implementation follows OAuth 2.0 best practices

Dependencies

• google_sign_in: ^6.1.5
• http: ^1.1.0
• jwt_decoder: ^2.0.1
• shared_preferences: ^2.2.1

Notes

• Make sure to configure your Google Cloud Console project properly
• Update the backend API URL before running the app
• Handle token expiration and refresh tokens as needed
• Implement proper error handling in production