Flutter -在小部件树中检测到重复的GlobalKey

Question

参考这个Duplicate GlobalKey detected in widget tree，当我从屏幕A导航到屏幕B并再次导航到屏幕A时，我仍然有重复键的困难

LoginPage

class LoginPage extends StatefulWidget {
  @override
  _LoginPageState createState() => _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {
  @override
  void initState() {
    super.initState();
//UsingSharedPreference , If Already Login , GoToHomePage
    Provider.of<LoginChangeNotifier>(context, listen: false)
        .checkLogin(context); 
  }

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

  @override
  Widget build(BuildContext context) {
    var _size = Screen(MediaQuery.of(context).size);
    return Consumer<LoginChangeNotifier>(
      builder: (context, login, _) {
        return Scaffold(
          key:Provider.of<LoginChangeNotifier>(context, listen: false)
              .scaffoldLoginKey,
          backgroundColor: Colors.black,
          body: Container(
              child: SingleChildScrollView(
            child: Column(
              mainAxisSize: MainAxisSize.max,
              children: <Widget>[
                Container(
                ),
                SizedBox(height: _size.hp(2)),
                Form(
                  key: Provider.of<LoginChangeNotifier>(context, listen: false)
                      .loginKey,
                  child:Container(
                    margin: EdgeInsets.symmetric(horizontal: _size.wp(8)),
                    child: Column(
                      children: <Widget>[
                        TextFormField(
                          controller: login.controllerEmail,
                          ),
                          keyboardType: TextInputType.emailAddress,
                          autovalidate: login.autoValidate,
                          validator: (e) {
                            if (e.isEmpty) {
                              return "Cant Be Empty";
                            } else {
                              return null;
                            }
                          },
                        ),
                        SizedBox(height: 16),
                        TextFormField(
                          controller: login.controllerPassword,
                            labelText: 'Password',
                          ),
                          keyboardType: TextInputType.emailAddress,
                          obscureText: login.secureText,
                          autovalidate: login.autoValidate,
                          validator: (e) {
                            if (e.isEmpty) {
                              return "Cant Be Empty";
                            } else {
                              return null;
                            }
                          },
                        ),
RaisedButton(
                                color: myPrimaryColor,
                                  children: <Widget>[
                                    Text("Login",
                                        style: TextStyle(
                                            color: Colors.black,
                                            fontFamily: "NunitoSansBold")),
                                  ],
                                ),
                                padding:
                                    EdgeInsets.only(top: 16.0, bottom: 16.0),
                                onPressed: () {
                                  print("clicked Button Login");
//HereHandleFromProvider
                                  login.authenticationUser(context);
                                },
                              ),
                        SizedBox(height: _size.hp(3)),
                        ),
                      ],
                    ),
                  ),
                ),
              ],
            ),
          )),
        );
      },
    );
  }

Login_Provider

class LoginChangeNotifier with ChangeNotifier {
  GlobalKey<ScaffoldState> _scaffoldLoginKey = GlobalKey<ScaffoldState>(
      debugLabel: '_scaffoldLoginkey');
  GlobalKey<FormState> _loginKey = new GlobalKey<FormState>();

 GlobalKey<ScaffoldState> get scaffoldLoginKey => _scaffoldLoginKey;
  GlobalKey<FormState> get loginKey => _loginKey;

authenticationUser(BuildContext context) async {
showDialog(
              context: context,
              builder: (myContext) =>
                  AlertDialog(
                    title: new Text('Warning'),
                    content: new Text('Your Password Expired'),
                    actions: [
                      new FlatButton(
                          onPressed: () {
                            Navigator.of(context).pushReplacement(
                                MaterialPageRoute(builder: (context) =>
//MoveToScreenB
                                    ChangePasswordPage()));
                          },
                          child: new Text(
                            'Change Password',
                            style: TextStyle(color: Colors.lightBlue),
                          ))
                    ],
                    shape: RoundedRectangleBorder(
                      side: BorderSide(color: Colors.white70, width: 1),
                      borderRadius: BorderRadius.circular(10),
                    ),
                  ));
}

ChangePasswordPage

class ChangePasswordPage extends StatelessWidget {
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Change Password", style: TextStyle(color: Colors.black)),
        centerTitle: true,
        iconTheme: IconThemeData(color: Colors.white),
      ),
      key: Provider.of<ChangePasswordNotifier>(context, listen: false)
          .scaffoldChangePasswordKey,
      body: Consumer<ChangePasswordNotifier>(
        builder: (context, changePassword, _) {
          return changePassword.changePasswordProcess
              ? Center(child: CircularProgressIndicator())
              : Padding(
                  padding: EdgeInsets.symmetric(
                  ),
                  child: Form(
                    key: Provider.of<ChangePasswordNotifier>(context,
                            listen: false)
                        .changePasswordkey,
                    child: Column(
                      children: [
                        TextFormField(),
                        SizedBox(
                            height: MediaQuery.of(context).size.height / 47),
                        TextFormField(),
                        SizedBox(
                            height: MediaQuery.of(context).size.height / 47),
                        TextFormField(),
                      ],
                    ),
                  ),
                );
        },
      ),
      bottomNavigationBar: BottomAppBar(
        elevation: 0.0,
        child: Padding(
            padding: const EdgeInsets.all(8.0),
            child: Consumer<ChangePasswordNotifier>(
              builder: (context, changePassword, _) {
                return RaisedButton(
                    onPressed: () {
                      print("Submit ChangePassword Clicked");
                      changePassword.changePasswordProcess
                          ? null
//HereHandleOnProvider
                          : changePassword.check(context);
                    },
                    child: Row(
                      children: <Widget>[
                        Text("SUBMIT",)
                      ],
                    ));
              },
            )),
      ),
    );
  }
}

ChangePasswordProvider

class ChangePasswordNotifier with ChangeNotifier {
  GlobalKey<ScaffoldState> _scaffoldChangePasswordKey = new GlobalKey<ScaffoldState>();
  GlobalKey<FormState> _changePasswordkey =new GlobalKey<FormState>();

  GlobalKey<FormState> get changePasswordkey => _changePasswordkey;
  GlobalKey<ScaffoldState> get scaffoldChangePasswordKey =>
      _scaffoldChangePasswordKey;

      check(BuildContext context) async {
confirmationPassword(context, "Success");
        }

        confirmationPassword(BuildContext context, result)async{
           var _providerLogin =
        Provider.of<LoginChangeNotifier>(context, listen: false);
          showDialog(
        context: context,
        builder: (myContext) => AlertDialog(
              title: new Text("Confirmation"),
              content: new Text(result),
              actions: [
                new FlatButton(
                    onPressed: () {
                      print("Clicked on Confirmation Password");
                      Navigator.pushAndRemoveUntil(
                          context,
                          //Here i Want to navigate back to Screen A
                          MaterialPageRoute(builder: (context) => LoginPage()),
                              (Route<dynamic> route) => false);
                    },
                    child: new Text(
                      'OK',
                      style: TextStyle(color: Colors.lightBlue),
                    ))
              ],
              shape: RoundedRectangleBorder(
                side: BorderSide(color: Colors.white70, width: 1),
                borderRadius: BorderRadius.circular(10),
              ),
            ));
        }

}

单击导航到屏幕A时结果

======== Exception caught by widgets library =======================================================
The following assertion was thrown building Form-[LabeledGlobalKey<FormState>#57f0a](state: FormState#c57b1):
'package:flutter/src/widgets/will_pop_scope.dart': Failed assertion: line 61 pos 12: '_route == ModalRoute.of(context)': is not true.


Either the assertion indicates an error in the framework itself, or we should provide substantially more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
  https://github.com/flutter/flutter/issues/new?template=BUG.md

The relevant error-causing widget was: 
  Form-[LabeledGlobalKey<FormState>#57f0a] file:///urlFile:login_page.dart:37:17
When the exception was thrown, this was the stack: 
#2      _WillPopScopeState.didUpdateWidget (package:flutter/src/widgets/will_pop_scope.dart:61:12)
#3      StatefulElement.update (package:flutter/src/widgets/framework.dart:4815:58)
#4      Element.updateChild (package:flutter/src/widgets/framework.dart:3314:15)
#5      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4652:16)
#6      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4800:11)
...
====================================================================================================

======== Exception caught by widgets library =======================================================
The following assertion was thrown while finalizing the widget tree:
Duplicate GlobalKey detected in widget tree.

The following GlobalKey was specified multiple times in the widget tree. This will lead to parts of the widget tree being truncated unexpectedly, because the second time a key is seen, the previous instance is moved to the new location. The key was:
- [LabeledGlobalKey<ScaffoldState>#14011]
This was determined by noticing that after the widget with the above global key was moved out of its previous parent, that previous parent never updated during this frame, meaning that it either did not update at all or updated before the widget was moved, in either case implying that it still thinks that it should have a child with that global key.
The specific parent that did not update after having one or more children forcibly removed due to GlobalKey reparenting is:
- Consumer<LoginChangeNotifier>(dependencies: [_LocalizationsScope-[GlobalKey#f6126], InheritedProvider<LoginChangeNotifier>, _InheritedTheme])
A GlobalKey can only be specified on one widget at a time in the widget tree.
When the exception was thrown, this was the stack: 
#0      BuildOwner.finalizeTree.<anonymous closure> (package:flutter/src/widgets/framework.dart:2881:15)
#1      BuildOwner.finalizeTree (package:flutter/src/widgets/framework.dart:2906:8)
#2      WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:915:18)
#3      RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:302:5)
#4      SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1117:15)
...
====================================================================================================

=====EDITED=====对于临时解决方案，我想使用重复的pop上下文(1个用于关闭警告对话框，1个用于返回页面A)，但我想这不是一个最佳实践。

Navigator.pop(context); 
Navigator.pop(context);

Answer 1

您可能希望考虑将GlobalKeys移动到页面中，以便在不再使用它们时将其处理掉，而不是在ChangeNotifier中初始化它们。然后，您可以只在authenticationUser()上传递导航键，以便在需要时访问导航器。

final navigatorKey = GlobalKey<NavigatorState>();

要从键访问Navigator，您可以使用类似的命令。

navigatorKey.currentState!.pushAndRemoveUntil(context,
    MaterialPageRoute(builder: (context) => LoginPage()),
        (Route<dynamic> route) => false);