关于ChangeNotifier提供程序

Question

我正在使用提供程序管理状态，但ChangeNotificationerProvider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ChangeNotificationerProvider不向我提供更新值，而是总是返回_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: '[e-mail]', 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

您创建了两个不同的AuthServices实例。

一个在State类的开头，另一个使用ChangeNotifierProvider。当调用_registerNewUser时，您使用在您的状态类中创建的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的值不会更改。

尝试删除状态类创建的AuthServices实例，并将ChangeNotifierProvider向上移动到小部件树中，以便所有函数共享AuthServices的同一实例。