我的“主”窗口小部件必须具有全局密钥。如果使用pushNamed或等效名称导航到它，它将在小部件树中生成有关重复键的异常。我只能pop到此小部件，但这严重降低了我的导航选项和小部件的可重用性。
我提供了一个小复制案例的来源，运行该应用程序，单击主页上的Login按钮，输入3个字符的登录名和3个字符的密码，然后输入Login。 / p>
有什么想法吗？没有GlobalKey的重新设计是一项艰巨的任务。
flutter: ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
flutter: The following assertion was thrown while finalizing the widget tree:
flutter: Duplicate GlobalKey detected in widget tree.
flutter: The following GlobalKey was specified multiple times in the widget tree. This will lead to parts of
flutter: the widget tree being truncated unexpectedly, because the second time a key is seen, the previous
flutter: instance is moved to the new location. The key was:
flutter: - [GlobalKey#1c91e navKey]
flutter: This was determined by noticing that after the widget with the above global key was moved out of its
flutter: previous parent, that previous parent never updated during this frame, meaning that it either did
flutter: not update at all or updated before the widget was moved, in either case implying that it still
flutter: thinks that it should have a child with that global key.
flutter: The specific parent that did not update after having one or more children forcibly removed due to
flutter: GlobalKey reparenting is:
flutter: - Semantics(container: false, properties: SemanticsProperties, label: null, value: null, hint: null,
flutter: hintOverrides: null, renderObject: RenderSemanticsAnnotations#147f5 NEEDS-PAINT)
flutter: A GlobalKey can only be specified on one widget at a time in the widget tree.
flutter:
flutter: When the exception was thrown, this was the stack:
flutter: #0 BuildOwner.finalizeTree.<anonymous closure>
flutter: #1 BuildOwner.finalizeTree
flutter: #2 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame
flutter: #3 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback
flutter: #4 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback
flutter: #5 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame
flutter: #6 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame
flutter: #10 _invoke (dart:ui/hooks.dart:236:10)
flutter: #11 _drawFrame (dart:ui/hooks.dart:194:3)
flutter: (elided 3 frames from package dart:async)
flutter: ════════════════════════════════════════════════════════════════════════════════════════════════════
flutter: Another exception was thrown: Multiple widgets used the same GlobalKey.
import 'package:flutter/material.dart';
class MyKeys {
static final GlobalKey navKey = GlobalKey<NavigatorState>(debugLabel: 'navKey');
}
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
routes: {
"/": (_) => MyHomePage(key: MyKeys.navKey, title: 'Home Page'),
'/auth': (_) => MyAuth(),
},
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
FlatButton(
child: Text('Login'),
onPressed: () => Navigator.of(context).pushNamed('/auth'),
),
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.display1,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
class MyAuth extends StatefulWidget {
@override
_MyAuthState createState() => _MyAuthState();
}
class _MyAuthState extends State<MyAuth> {
String login;
String password;
final _formKey = GlobalKey<FormState>();
void _doLogin() {
final form = _formKey.currentState;
if(form.validate()) {
form.save();
Navigator.of(context).pushNamed('/');
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Login')),
body: Padding(
padding: const EdgeInsets.all(24.0),
child: Form(
key: _formKey,
child: Column(
children: <Widget>[
TextFormField(
decoration: InputDecoration(
labelText: 'Enter login',
),
autocorrect: false,
autofocus: true,
validator: (v) => v.trim().length < 3 ? 'Enter more than 3 chars': null,
onSaved: (v) => login = v.trim(),
),
TextFormField(
decoration: InputDecoration(
labelText: 'Enter password',
),
obscureText: true,
autocorrect: false,
validator: (v) => v.trim().length < 3 ? 'Password should be no less than 3 chars': null,
onSaved: (v) => password = v.trim(),
),
FlatButton(
child: Text('Login'),
onPressed: () => _doLogin(),
)
],
),
),
),
);
}
}
答案 0 :(得分：0)
使用pushNamed时，新路由会添加到现有路由的顶部。
您可以使用pushReplacementNamed而不是pushNamed，因此现有的窗口小部件将从导航堆栈中删除，并用新的替换。