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Question

Description:

I’m working on a Flutter application where I have an AuthService class for handling user authentication and a LogInScreen for the login UI. When the login fails, I’m trying to display an error message on the LogInScreen. However, I keep encountering a generic “Unknown error” message instead of the actual error message from the server.

Here’s my AuthService and LogInScreen code:

AuthService:

import 'dart:async';
import 'dart:convert';
import 'package:demo/core/constants/constants.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:shared_preferences/shared_preferences.dart';

class AuthService extends ChangeNotifier {
  Timer? _authTimer;
  DateTime? _expiryDate;
  String? _token;

  String? get token => _token ?? '';

  Future<void> login(
    String username,
    String password, {
    required bool rememberMe,
  }) async {
    final url = Uri.parse('${AppConstants.baseURL}/auth/login');
    final response = await http.post(
      url,
      headers: {
        'Content-Type': 'application/json',
        'Accept': 'application/json',
      },
      body: jsonEncode({
        'username': username,
        'password': password,
      }),
    );

    if (response.statusCode != 200) {
      final responseData = jsonDecode(response.body);
      final errorMessage = responseData['message'] ?? 'Unknown error';
      throw Exception(errorMessage);
    }

    final responseData = jsonDecode(response.body);
    _token = responseData['token'];
    final expiresIn = responseData['expires_in'];

    _expiryDate = expiresIn != null && expiresIn is int
        ? DateTime.now().add(Duration(seconds: expiresIn))
        : DateTime.now().add(const Duration(hours: 4));

    await _persistToken(_token!, _expiryDate!);
  }

  Future<void> refreshToken() async {
    final url = Uri.parse('${AppConstants.baseURL}/auth/refresh');
    final response = await http.post(
      url,
      headers: {
        'Authorization': 'Bearer $_token',
        'Content-Type': 'application/json',
        'Accept': 'application/json',
      },
    );

    if (response.statusCode != 200) {
      throw Exception('Failed to refresh token: ${response.reasonPhrase}');
    }

    final responseData = jsonDecode(response.body);
    _token = responseData['token'];
    final expiresIn = responseData['expires_in'];
    _expiryDate = DateTime.now().add(Duration(seconds: expiresIn));

    await _persistToken(_token!, _expiryDate!);
  }

  Future<bool> isLoggedIn() async {
    await _loadPersistedToken();
    return _token != null;
  }

  Future<void> logout() async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.remove('token');
    await prefs.remove('expiryDate');
    _token = null;
    _expiryDate = null;
    _authTimer?.cancel();
    _authTimer = null;
    notifyListeners();
  }

  Future<void> _persistToken(String token, DateTime expiryDate) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString('token', token);
    await prefs.setString('expiryDate', expiryDate.toIso8601String());
    _token = token;
    _expiryDate = expiryDate;
    _autoLogout();
    notifyListeners();
  }

  Future<void> _loadPersistedToken() async {
    final prefs = await SharedPreferences.getInstance();
    _token = prefs.getString('token');
    final expiryDateString = prefs.getString('expiryDate');

    if (expiryDateString == null) {
      notifyListeners();
      return;
    }

    _expiryDate = DateTime.parse(expiryDateString);

    if (_expiryDate!.isBefore(DateTime.now())) {
      await refreshToken();
    }

    notifyListeners();
  }

  void _autoLogout() {
    _authTimer?.cancel();

    if (_expiryDate == null) return;

    final timeToExpiry = _expiryDate!.difference(DateTime.now()).inSeconds;
    _authTimer = Timer(Duration(seconds: timeToExpiry), logout);
  }
}

LogInScreen:

import 'package:demo/core/constants/app_colors.dart';
import 'package:demo/core/constants/constants.dart';
import 'package:demo/ui/screens/applicants/views/applicant_form_screen.dart';
import 'package:demo/ui/widgets/re_usable_widgets/re_usable_widgets.dart';
import 'package:demo/ui/widgets/ui_widgets/custom_app_bar.dart';
import 'package:demo/ui/widgets/ui_widgets/custom_clipper.dart';
import 'package:demo/ui/widgets/ui_widgets/error_message.dart';
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../../../core/providers/password_visibility_provider.dart';

class LogInScreen extends ConsumerStatefulWidget {
  const LogInScreen({super.key});

  @override
  _LogInScreenState createState() => _LogInScreenState();
}

class _LogInScreenState extends ConsumerState<LogInScreen> {
  String? _errorMessage;
  final _formKey = GlobalKey<FormState>();
  bool _isLoading = true;
  late TextEditingController _passwordController;
  bool _rememberMe = false;
  late TextEditingController _userNameController;

  @override
  void dispose() {
    _userNameController.dispose();
    _passwordController.dispose();
    super.dispose();
  }

  @override
  void initState() {
    super.initState();
    _userNameController = TextEditingController();
    _passwordController = TextEditingController();
    _checkLoginStatus();
  }

  Future<void> _checkLoginStatus() async {
    final isLoggedIn = await ref.read(authProvider).isLoggedIn();
    if (!isLoggedIn) {
      setState(() {
        _isLoading = false;
      });
    } else {
      Navigator.pushReplacement(
        context,
        MaterialPageRoute(builder: (_) => const ApplicantFormScreen()),
      );
    }
  }

  Future<void> _onSubmit() async {
    setState(() {
      _errorMessage = null;
    });

    if (!_formKey.currentState!.validate()) return;

    final name = _userNameController.text;
    final password = _passwordController.text;

    try {
      await ref
          .read(authProvider)
          .login(name, password, rememberMe: _rememberMe);

      Navigator.pushReplacement(
        context,
        MaterialPageRoute(builder: (_) => const ApplicantFormScreen()),
      );
    } catch (e) {
      setState(() {
        _errorMessage = e.toString();
      });
    }
  }

  SizedBox _buildLoginButton() {
    return SizedBox(
      width: double.infinity,
      child: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 150.0),
        child: ElevatedButton(
          style: ElevatedButton.styleFrom(
            padding: const EdgeInsets.symmetric(vertical: 20),
            backgroundColor: AppColors.kBlueColor,
            shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.circular(8.0)),
          ),
          onPressed: _onSubmit,
          child: const Text(
            'LOGIN',
            style: TextStyle(
              fontSize: 16.0,
              color: AppColors.kwhite,
              fontWeight: FontWeight.bold,
            ),
          ),
        ),
      ),
    );
  }

  void _handleErrorMessageClose() {
    setState(() {
      _errorMessage = null;
    });
  }

  @override
  Widget build(BuildContext context) {
    final obscureText = ref.watch(obscureTextProvider);
    final Size size = MediaQuery.of(context).size;

    return SafeArea(
      child: Scaffold(
        backgroundColor: Theme.of(context).scaffoldBackgroundColor,
        body: _isLoading
            ? const Center(child: CircularProgressIndicator())
            : Row(
                children: [
                  Expanded(
                    child: Container(
                      color: AppColors.kwhite,
                      child: Center(
                        child: Column(
                          mainAxisSize: MainAxisSize.min,
                          children: [
                            SizedBox(
                              height: size.height * 0.250,
                              child: Image.asset(
                                AppConstants.solidCheckLogo,
                                fit: BoxFit.contain,
                              ),
                            ),
                          ],
                        ),
                      ),
                    ),
                  ),
                  Expanded(
                    child: ClipPath(
                      clipper: CustomClipPath(),
                      child: Container(
                        height: size.height,
                        width: size.width,
                        decoration: const BoxDecoration(
                          gradient: LinearGradient(
                            colors: [
                              Color(0xFF014F8C),
                              Color(0xFF0EDCF8),
                            ],
                          ),
                        ),
                        child: SizedBox(
                          child: Center(
                            child: Form(
                              key: _formKey,
                              child: Padding(
                                padding: const EdgeInsets.only(left: 50.0),
                                child: Container(
                                  height: size.height * 0.70,
                                  width: size.width * 0.34,
                                  decoration: BoxDecoration(
                                    color: Colors.white.withOpacity(0.5),
                                    borderRadius: BorderRadius.circular(10.0),
                                  ),
                                  child: Center(
                                    child: Column(
                                      mainAxisSize: MainAxisSize.min,
                                      crossAxisAlignment:
                                          CrossAxisAlignment.center,
                                      mainAxisAlignment:
                                         

 MainAxisAlignment.center,
                                      children: [
                                        Padding(
                                          padding: const EdgeInsets.symmetric(
                                            horizontal: 60.0,
                                          ),
                                          child: ReusableWidgets.buildTextField(
                                            controller: _userNameController,
                                            fieldTitle: 'Username',
                                            hintText: 'Enter your username',
                                            context: context,
                                          ),
                                        ),
                                        const SizedBox(height: 20.0),
                                        Padding(
                                          padding: const EdgeInsets.symmetric(
                                            horizontal: 60.0,
                                          ),
                                          child: ReusableWidgets.buildTextField(
                                            controller: _passwordController,
                                            fieldTitle: 'Password',
                                            hintText: 'Enter your password',
                                            isPassword: true,
                                            obscureText: obscureText,
                                            context: context,
                                            toggleVisibility: () => ref
                                                .read(obscureTextProvider.notifier)
                                                .toggle(),
                                          ),
                                        ),
                                        const SizedBox(height: 20.0),
                                        Padding(
                                          padding: const EdgeInsets.symmetric(
                                            horizontal: 60.0,
                                          ),
                                          child: Row(
                                            mainAxisAlignment:
                                                MainAxisAlignment.center,
                                            children: [
                                              Checkbox(
                                                activeColor:
                                                    AppColors.kBlueColor,
                                                value: _rememberMe,
                                                onChanged: (value) {
                                                  setState(() {
                                                    _rememberMe = value ?? false;
                                                  });
                                                },
                                              ),
                                              const Text('Remember Me'),
                                            ],
                                          ),
                                        ),
                                        if (_errorMessage != null)
                                          Padding(
                                            padding: const EdgeInsets.symmetric(
                                              horizontal: 16.0,
                                            ),
                                            child: ErrorMessageWidget(
                                              errorMessage: _errorMessage,
                                              onClose: _handleErrorMessageClose,
                                            ),
                                          ),
                                        const SizedBox(height: 10.0),
                                        const SizedBox(height: 40),
                                        _buildLoginButton(),
                                      ],
                                    ),
                                  ),
                                ),
                              ),
                            ),
                          ),
                        ),
                      ),
                    ),
                  ),
                ],
              ),
      ),
    );
  }
}

Any help on fixing this issue would be greatly appreciated. Thank you!

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Danh mục

Flutter AuthService Error Handling Not Displaying Correct Message from API