找不到材料构件
找不到材料构件
提问于 2017-05-13 07:03:06
我是Flutter的新手，我正在尝试执行示例here。我只想使用TextField小部件来获取一些用户输入。问题是我得到了一个"No Material widget found“。错误。我做错了什么？谢谢。
代码：
import 'package:flutter/material.dart';
void main() {
runApp(new MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
home: new ExampleWidget(),
);
}
}
/// Opens an [AlertDialog] showing what the user typed.
class ExampleWidget extends StatefulWidget {
ExampleWidget({Key key}) : super(key: key);
@override
_ExampleWidgetState createState() => new _ExampleWidgetState();
}
/// State for [ExampleWidget] widgets.
class _ExampleWidgetState extends State<ExampleWidget> {
final TextEditingController _controller = new TextEditingController();
@override
Widget build(BuildContext context) {
return new Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new TextField(
controller: _controller,
decoration: new InputDecoration(
hintText: 'Type something',
),
),
new RaisedButton(
onPressed: () {
showDialog(
context: context,
child: new AlertDialog(
title: new Text('What you typed'),
content: new Text(_controller.text),
),
);
},
child: new Text('DONE'),
),
],
);
}
}这是错误堆栈：
Launching lib/main.dart on Android SDK built for x86 in debug mode...
Built build/app/outputs/apk/app-debug.apk (21.5MB).
I/flutter ( 5187): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 5187): The following assertion was thrown building InputDecorator(decoration: InputDecoration(hintText:
I/flutter ( 5187): "Type something"); baseStyle: null; isFocused: false; isEmpty: true; dirty):
I/flutter ( 5187): No Material widget found.
I/flutter ( 5187): InputDecorator widgets require a Material widget ancestor.
I/flutter ( 5187): In material design, most widgets are conceptually "printed" on a sheet of material. In Flutter's
I/flutter ( 5187): material library, that material is represented by the Material widget. It is the Material widget
I/flutter ( 5187): that renders ink splashes, for instance. Because of this, many material library widgets require that
I/flutter ( 5187): there be a Material widget in the tree above them.
I/flutter ( 5187): To introduce a Material widget, you can either directly include one, or use a widget that contains
I/flutter ( 5187): Material itself, such as a Card, Dialog, Drawer, or Scaffold.
I/flutter ( 5187): The specific widget that could not find a Material ancestor was:
I/flutter ( 5187): InputDecorator(decoration: InputDecoration(hintText: "Type something"); baseStyle: null;
I/flutter ( 5187): isFocused: false; isEmpty: true)
I/flutter ( 5187): The ownership chain for the affected widget is:
I/flutter ( 5187): InputDecorator ← AnimatedBuilder ← Listener ← _GestureSemantics ← RawGestureDetector ←
I/flutter ( 5187): GestureDetector ← TextField ← Column ← ExampleWidget ← _ModalScopeStatus ← ⋯
I/flutter ( 5187):
I/flutter ( 5187): When the exception was thrown, this was the stack:
I/flutter ( 5187): #0 debugCheckHasMaterial.<anonymous closure> (package:flutter/src/material/debug.dart:26)
I/flutter ( 5187): #2 debugCheckHasMaterial (package:flutter/src/material/debug.dart:23)
I/flutter ( 5187): #3 InputDecorator.build (package:flutter/src/material/input_decorator.dart:334)
... <output omitted>
I/flutter ( 5187): (elided one frame from class _AssertionError)
I/flutter ( 5187): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 5187): Another exception was thrown: No Material widget found.回答 6
Stack Overflow用户
发布于 2020-03-13 13:23:07
在我的示例中，我在scaffold中使用了一个英雄小部件-如下所示
Scaffold(
body:Hero(
child:ListView(
children:<Widget>[
TextField(),
...
...
]
)
)
);我只需将Hero Widget移到Scaffold之外，它就解决了问题
Hero(
child:Scaffold(
body:ListView(
children:<Widget>[
TextField(),
...
...
]
)
)
);Stack Overflow用户
发布于 2020-05-05 22:35:10
将您的小部件放入一个脚手架中，如下所示：
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Demo',
//home: MyWidget(), --> do not do this !!!
home: Home() --> this will wrap it in Scaffold
);
}
}
class Home extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Demo'),
),
body: MyWidget()); --> put your widget here
}
}
class MyWidget extends StatefulWidget {
...Stack Overflow用户
发布于 2019-09-06 19:10:04
该错误意味着您必须将列包装在Material小部件中，您可以将其作为主体放置到脚手架上，或者将其作为Materialapp的主页放置。例如：
return MaterialApp(
home: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
TextField(
controller: _controller,
decoration: new InputDecoration(hintText: 'Type something'),
),
]
),
);或
return MaterialApp(
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
TextField(
controller: _controller,
decoration: new InputDecoration(hintText: 'Type something'),
),
]
),
);页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/43947552
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