Flutter BLoC身份验证

abstract class AuthEvent {
  const AuthEvent();
}

class LoginEvent extends AuthEvent {
  final String email;
  final String password;

  LoginEvent(this.email, this.password);
}

class LogoutEvent extends AuthEvent {
  const LogoutEvent();
}

abstract class AuthState {
  const AuthState();
}

class AuthInitial extends AuthState {}

class AuthLoading extends AuthState {}

class AuthSuccess extends AuthState {
  final String token;

  AuthSuccess(this.token);
}

class AuthFailure extends AuthState {
  final String message;

  AuthFailure(this.message);
}

class AuthBloc extends Bloc<AuthEvent, AuthState> {
  AuthBloc() : super(AuthInitial());

  @override
  Stream<AuthState> mapEventToState(AuthEvent event) async* {
    if (event is LoginEvent) {
      yield AuthLoading();
      try {
        // 模拟登录请求
        final token = await login(event.email, event.password);
        yield AuthSuccess(token);
      } catch (e) {
        yield AuthFailure(e.toString());
      }
    } else if (event is LogoutEvent) {
      yield AuthInitial();
    }
  }

  Future<String> login(String email, String password) async {
    // 模拟登录逻辑
    await Future.delayed(Duration(seconds: 2));
    if (email == 'user@example.com' && password == 'password') {
      return 'auth_token';
    } else {
      throw Exception('Invalid email or password');
    }
  }
}

class LoginScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final authBloc = BlocProvider.of<AuthBloc>(context);

    return Scaffold(
      appBar: AppBar(
        title: Text('Login'),
      ),
      body: BlocBuilder<AuthBloc, AuthState>(
        builder: (context, state) {
          if (state is AuthLoading) {
            return Center(child: CircularProgressIndicator());
          } else if (state is AuthSuccess) {
            return Center(child: Text('Logged in successfully'));
          } else if (state is AuthFailure) {
            return Center(child: Text('Login failed: ${state.message}'));
          } else {
            return Column(
              children: [
                TextField(
                  decoration: InputDecoration(labelText: 'Email'),
                  onChanged: (email) {
                    // 更新BLoC中的email
                  },
                ),
                TextField(
                  decoration: InputDecoration(labelText: 'Password'),
                  obscureText: true,
                  onChanged: (password) {
                    // 更新BLo::c中的password
                  },
                ),
                ElevatedButton(
                  onPressed: () {
                    authBloc.add(LoginEvent('user@example.com', 'password'));
                  },
                  child: Text('Login'),
                ),
              ],
            );
          }
        },
      ),
    );
  }
}