本文介绍了找不到材料小部件的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我不熟悉Flutter,并且尝试在此处处执行示例.我只想使用TextField小部件来获取一些用户输入.问题是我得到找不到材料小部件".错误.我究竟做错了什么 ?谢谢.
I am new to Flutter and I was trying do execute the example here. I just want to use the TextField widget to get some user input. The issue is that I get a "No Material widget found." error. What am I doing wrong ? Thank you.
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.
推荐答案
错误消息显示:
就您而言,我可能会将您的Column
包装在Scaffold
中.这样一来,以后便可以轻松地将其他重要的小部件添加到您的应用中,例如AppBar
,Drawer
或FloatingActionButton
.
In your case, I'd probably wrap your Column
in a Scaffold
. This will make it easy to add other material widgets to your app later, such as an AppBar
, Drawer
, or FloatingActionButton
.
@override
Widget build(BuildContext context) {
return new Scaffold(
body: 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'),
),
],
),
);
}
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