flutter - 我对 Flutter Provider Architecture 的错误是什么，因为它一直在无限地重建？

Question

我对提供程序架构有什么误解？

我的入口点：

void main() {
  runApp(
    MultiProvider(
      providers: [
        ChangeNotifierProvider<AuthProvider>(
            create: (context) => AuthProvider()),
        ChangeNotifierProvider<UserProvider>(
            create: (context) => UserProvider()),
      ],
      child: BdopsApp(),
    ),
  );
}

class BdopsApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.teal,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      initialRoute: LoginView.routeName,
      routes: {
        HomepageView.routeName: (context) => HomepageView(),
        LoginView.routeName: (context) => LoginView(),
      },
    );
  }
}

首先，我使用我的登录凭据登录。

class LoginView extends StatelessWidget {
  static const routeName = 'LoginView';

  final GlobalKey<FormState> _formKey = GlobalKey<FormState>();

  final User _user = User();

  @override
  Widget build(BuildContext context) {
    return Consumer<AuthProvider>(
      builder: (_, data, __) => Scaffold(
        appBar: CustomAppBar.getAppBar(
          title: 'BDOPS',
          subTitle: 'LOG IN',
        ),
        drawer: SidveNavDrawer(),
        body: Form(
          key: _formKey,
          child: Padding(
            padding: EdgeInsets.symmetric(horizontal: 20.0),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                FormInputTextBox(
                  labelText: 'Email',
                  hintText: '[e-mail]',
                  validator: (value) {
                    if (value == null) {
                      return 'Login email not provided';
                    }
                    if (!RegExp(xEmailRegx).hasMatch(value)) {
                      return 'Not a valid email address';
                    }
                  },
                  onSaved: (value) {
                    _user.email = value.trim();
                  },
                ),
                FormInputTextBox(
                  labelText: 'Password',
                  hintText: '* * * * *',
                  isPassword: true,
                  validator: (value) {
                    if (value == null) {
                      return 'Login password not provided';
                    }
                    if (value.toString().length < 6) {
                      return 'Minmum length is six charector';
                    }
                  },
                  onSaved: (value) {
                    _user.password = value.trim();
                  },
                ),
                Divider(
                  height: 30.0,
                ),
                RaisedButton(
                  color: Colors.deepOrange,
                  padding: EdgeInsets.symmetric(vertical: 10.0),
                  onPressed: () async {
                    if (!_formKey.currentState.validate()) {
                      return;
                    }

                    _formKey.currentState.save();
                    var res = await data.loginUser(_user);

                    if (res == true) {
                      AlertDialog(
                        title: Text('Login Success'),
                      );
                    } else {
                      AlertDialog(
                        title: Text('Login Failed'),
                      );
                    }
                    Navigator.pushReplacementNamed(
                        context, HomepageView.routeName);
                  },
                  child: Text(
                    'SUBMIT',
                    style: xHeaderText,
                  ),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

然后我导航到主页，在页面加载时，屏幕应该从 AuthUser Provider 的 getAuthUser 中获取 Auth 用户，并自触发一个方法，使用 userID 从 API 获取登录用户的详细信息。

class HomepageView extends StatelessWidget {
  static const routeName = 'HomePageView';

  @override
  Widget build(BuildContext context) {
    final userId = Provider.of<AuthProvider>(context).getAuthUser.id;

    return Consumer<UserProvider>(
      builder: (_, dataProvider, __) {
        dataProvider.fetchAUser(userId);
        return Scaffold(
          appBar: CustomAppBar.getAppBar(title: 'BDOPS', subTitle: 'Home'),
          drawer: SidveNavDrawer(),
          body: Text(dataProvider.getSingelUser.email),
        );
      },
    );
  }
}

这样做，我的应用程序首先抛出一个错误，然后一遍又一遍地重建和调用 API。

我的提供者课程是：

class AuthProvider with ChangeNotifier {
  User _authUser;
  String _errorMessage;
  AuthTokens _tokens;

  Future<bool> loginUser(User user) async {
    if (user.email == null || user.password == null) {
      _setErrorMessage('Provide login credentials');
    }
    var resp = await APIService().loginUser(
      email: user.email,
      password: user.password,
    );
    if (resp.statusCode == 200) {
      _setAuthToken(authTokensFromJson(resp.body));
      var userFetched =
          await UserProvider().fetchAUser(decodeJwt(_tokens.access)['user_id']);
      if (userFetched != null) {
        _setAuthUser(userFetched);
        return true;
      }
    }
    _setErrorMessage('Failed to login');
    return false;
  }

  void _setAuthToken(value) {
    _tokens = value;
  }

  void _setAuthUser(value) {
    _authUser = value;
    notifyListeners();
  }

  User get getAuthUser {
    return _authUser;
  }

  void _setErrorMessage(value) {
    _errorMessage = value;
    notifyListeners();
  }

  String get getErrorMessage {
    return _errorMessage;
  }
}

class UserProvider with ChangeNotifier {
  User _user;

  Future<User> fetchAUser(userId) async {
    var response = await APIService().getAUser(userId: userId);
    if (response.statusCode == 200) {
      setUser(userFromJson(response.body));

      print('Called from UserProvider');

      return _user;
    }
    return null;
  }

  void setUser(value) {
    _user = value;
    notifyListeners();
  }

  User get getSingelUser {
    return _user;
  }
}

标签： flutterflutter-providerstate-managementstatelesswidget