关于 ChangeNotifier 提供者

Question

我正在使用提供程序管理状态，但 ChangeNotifierProvider 不会更改变量的值。我想在用户注册时显示进度指示器。但是 ChangeNotifierProvider 不给我提供更新值，而是它总是 return 我 _isLoading = false; 我的代码：

AuthServices.dart

class AuthServices with ChangeNotifier {
  bool _isLoading = false;

  bool get loading => _isLoading;

  ///Register User
  Future registerUser(
      {@required String email, @required String password}) async {
    try {
      _isLoading = true;
      notifyListeners();

      await http.post(
          BackEndConfigs.baseUrl +
              BackEndConfigs.version +
              BackEndConfigs.auth +
              EndPoints.register,
          body: {
            "email": email,
            "password": password
          }).then((http.Response response) {
        _isLoading = false;
        notifyListeners();
        return RegisterUser.fromJson(json.decode(response.body));
      });
    } catch (e) {
      print(e);
    }
  }
}

RegisterScreen.dart

class RegisterScreen extends StatefulWidget {
  @override
  _RegisterScreenState createState() => _RegisterScreenState();
}

class _RegisterScreenState extends State<RegisterScreen> {
  AuthServices _authServices = AuthServices();
  ProgressDialog pr;
  @override
  Widget build(BuildContext context) {
    pr = ProgressDialog(context, isDismissible: true);
    // print(status.loading);

    return Scaffold(
      appBar:
          customAppBar(context, title: 'Register Yourself', onPressed: () {}),
      body: _getUI(context),
    );
  }

  Widget _getUI(BuildContext context) {
    return LoadingOverlay(
      isLoading: false,
      child: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 20.0),
        child: SingleChildScrollView(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.start,
            children: [
              VerticalSpace(10.0),
              GreyBoldText('Account Information'),
              VerticalSpace(20.0),
              IconsButtonRow([
                Icon(
                  FontAwesomeIcons.linkedinIn,
                  color: Color(0xff0e76a8),
                ),
                Icon(
                  FontAwesomeIcons.facebook,
                  color: Color(0xff3b5998),
                ),
                Icon(
                  FontAwesomeIcons.google,
                  color: Color(0xff4285F4),
                ),
              ]),
              VerticalSpace(10.0),
              GreyNormalText('or sign up with Email'),
              VerticalSpace(10.0),
              BlackBoldText("Email"),
              AppTextField(
                label: 'Email',
              ),
              BlackBoldText("Password"),
              AppTextField(
                label: 'Password',
              ),
              BlackBoldText("Confirm Password"),
              AppTextField(
                label: 'Confirm Password',
              ),
              VerticalSpace(20.0),
              ChangeNotifierProvider(
                create: (_) => AuthServices(),
                child: Consumer(
                  builder: (context, AuthServices user, _) {
                    return Text(user.loading.toString());
                  },
                ),
              ),
              AppButton(
                  buttonText: 'Next',
                  onPressed: () async {
                    // await pr.show();
                    _registerNewUser();
                  }),
              VerticalSpace(30.0),
              ToggleView(ToggleViewStatus.SignUpScreen),
              VerticalSpace(20.0),
            ],
          ),
        ),
      ),
    );
  }

  _registerNewUser() async {
    _authServices.registerUser(
        email: 'sdjfkldsdf@ssdfdsddfdgsffd.com', password: 'sldjsdfkls');
  }
}

main.dart

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
          scaffoldBackgroundColor: Colors.white,
          hintColor: FrontEndConfigs.hintColor,
          cursorColor: FrontEndConfigs.hintColor,
          fontFamily: 'Gilory'),
      home: RegisterScreen(),
    );
  }
}

Answer 1

您创建了 AuthServices 的两个不同实例。

一个在您的状态开始时 class，一个使用 ChangeNotifierProvider。调用 _registerNewUser 时，您使用的是在您的州 class 中创建的 AuthServices 而不是提供的

当您在第一个 AuthServices 上调用 registerUser 时，Widget 树中 ChangeNotifierProvider 提供的第二个 AuthServices 的值不会改变。

尝试删除由状态 class 创建的 AuthServices 实例并将您的 ChangeNotifierProvider 向上移动到小部件树，以便您的所有函数共享同一个 AuthServices 实例。

关于 ChangeNotifier 提供者

About ChangeNotifier Provider

flutter

provider

state-management