dart – InheritedWidget – 在navigator.push之后调用getter

概述导航到新窗口小部件后,我在尝试访问InheritedWidget时遇到问题. 我有这样的顶级小部件 class App extends StatelessWidget{ build(context){ return MaterialApp( title: 'Iniciar Sesion', home: LoginBlocProvider(child: W 导航到新窗口小部件后,我在尝试访问inheritedWidget时遇到问题. @H_404_7@

@H_404_7@我有这样的顶级小部件

@H_404_7@

class App extends StatelessWidget{  build(context){    return MaterialApp(        Title: 'Iniciar Sesion',home: LoginBlocProvIDer(child: WelcomeScreen()),);  }  }

@H_404_7@然后WelcomeScreen有一个导航到LoginScreen的按钮

@H_404_7@

class WelcomeScreen extends StatelessWidget {  @overrIDe Widget build(BuildContext context){    return Scaffold(      body: Center(child: Mybutton)    );  }}class Mybutton extends StatelessWidget {  @overrIDe  Widget build(BuildContext context) {    return Raisedbutton(      shape: Stadiumborder(),child: Text('Ingresar',style: TextStyle(color: colors.black)),elevation: 5.0,onpressed: () {         Navigator.of(context).push(MaterialPageRoute(           builder: (BuildContext context) =>LoginScreen()        ));      }    );  }}

@H_404_7@最后在LoginScreen中我想访问inheritedWidget

@H_404_7@

class LoginScreen extends StatefulWidget {  @overrIDe  _LoginScreenState createState() => _LoginScreenState();}class _LoginScreenState extends State<LoginScreen> {  LoginBloc bloc;    @overrIDe voID dIDChangeDependencIEs() {    bloc = LoginBlocProvIDer.of(context);    super.dIDChangeDependencIEs();  }  @overrIDe Widget build(BuildContext context){    return Scaffold(      body:      Stack(        fit: StackFit.expand,children: <Widget>[          positioned(            top: 0.0,child: Image.asset('assets/images/img.jpg',fit: BoxFit.none,),_buildLogin(),],);  }}

@H_404_7@编辑：这是LoginBlocProvIDer

@H_404_7@

class LoginBlocProvIDer extends inheritedWidget {  final bloc;  LoginBlocProvIDer({Key key,Widget child})   : bloc = LoginBloc(),super(key:key,child:child);  @overrIDe  bool updateShouldNotify(inheritedWidget oldWidget) => true;  static LoginBloc of(BuildContext context) {    return (context.inheritFromWidgetOfExactType(LoginBlocProvIDer) as LoginBlocProvIDer).bloc;  }}

@H_404_7@但是,当我运行inheritedWidget的.of方法时,我得到了这个错误

@H_404_7@

I/Flutter (27725): The following NoSuchMethodError was thrown building Builder:I/Flutter (27725): The getter 'bloc' was called on null.I/Flutter (27725): Receiver: nullI/Flutter (27725): TrIEd calling: bloc

@H_404_7@我的印象是,这一切都与Navigator.push构建器方法中的上下文有关.
因为如果我使用不带Navigator.push的LoginScreen小部件,我可以完美地使用inheritedWidget

@H_404_7@发生错误是因为传递给LoginBlocProvIDer.of()方法的上下文未找到实例.

@H_404_7@有什么想法吗？

解决方法 在您提供的代码中,LoginScreen不是LoginBlocProvIDer的后代,这就是它无法找到祖先小部件的原因.您的代码在LoginBlocProvIDer中包装WelcomeScreen路由,但不包括整个导航器.解决方案是将您的MaterialApp包装在LoginBlocProvIDer中,然后您可以在应用程序的任何位置访问它. @H_404_7@

@H_404_7@

class App extends StatelessWidget {  @overrIDe  Widget build(context) {    return LoginBlocProvIDer(      child: MaterialApp(        Title: 'Iniciar Sesion',home: WelcomeScreen(),);  }}

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