使用 Flutter 进行 Web 构建时，抛出了另一个异常：NoSuchMethodError：null 上的无效成员：'findRenderObject'继续发生

Question

使用 Flutter 执行 HotRestart 时，抛出了另一个异常。NoSuchMethodError： 无效的空成员： 'findRenderObject' 继续引发。

此错误在"颤振运行"后立即很好，但是如果您重写文本中的字符，将输出以下错误。

我尝试重新启动Google Chrome，重新运行Flutter，更新FlutterSDK，重新启动VisualStudioCode，在Android模拟器而不是网络上构建，但此错误从未消失。

import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'todo_list_for_web',
theme: ThemeData(
primarySwatch: Colors.grey,
),
home: RootPage(),
);
}
}
class RootPage extends StatefulWidget {
@override
_RootPageState createState() => _RootPageState();
}
class _RootPageState extends State<RootPage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Flutter Todo list"),
backgroundColor: Colors.black87,
),
body: Row(
children: <Widget>[
Expanded(
flex: 5,
child: Container(
height: double.infinity,
width: double.infinity,
color: Colors.white,
child: TaskListArea(),
),
),
Expanded(
flex: 3,
child: Container(
child: InfoWindows(),
),
)
],
));
}
}
class TaskListArea extends StatefulWidget {
@override
_TaskListAreaState createState() => _TaskListAreaState();
}
class _TaskListAreaState extends State<TaskListArea> {
List<String> tasks = [
"try making coffee",
"work on homework",
"do my paper",
];
@override
Widget build(BuildContext context) {
return Container(
color: Colors.green,
child: Stack(children: <Widget>[
Align(
alignment: Alignment.topLeft,
child: Padding(
//Title Text
padding: EdgeInsets.only(top: 18.0, left: 10.0, bottom: 30.0),
child: Text(
"Today's tasks.",
style: TextStyle(
fontSize: 30.0,
),
textAlign: TextAlign.start,
)),
),
Align(
alignment: Alignment.center,
child: Container(
height: 300.0,
child: ListView.separated(
separatorBuilder: (context, index) =>
Divider(color: Colors.black),
padding: EdgeInsets.all(16.0),
itemCount: tasks.length,
itemBuilder: (context, i) => Padding(
padding: EdgeInsets.all(8.0),
child: Center(child: Text(tasks[i]),)
)
)
)
),
Padding(
padding: EdgeInsets.all(50.0),
child: Align(
alignment: Alignment.bottomCenter,
child: Row(children: <Widget>[
Expanded(
flex: 20,
child: TextField(
decoration: InputDecoration(
hintText: "make coffee.",
border: UnderlineInputBorder(
borderSide: BorderSide(color: Colors.black),
)),
)),
Expanded(
child: SizedBox(
width: 10.0,
),
),
Expanded(
flex: 5,
child: FlatButton(
color: Colors.grey,
onPressed: () {},
child: Text("Add"),
))
])))
]));
}
}
class InfoWindows extends StatefulWidget {
@override
_InfoWindowsState createState() => _InfoWindowsState();
}
class _InfoWindowsState extends State<InfoWindows> {
@override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
Expanded(
flex: 1,
child: Container(
color: Colors.red,
)),
Expanded(
flex: 1,
child: Container(
color: Colors.blueGrey,
))
],
);
}
}

正在执行热重启...

Another exception was thrown: NoSuchMethodError:invalid member on null: 'findRenderObject'      
Performing hot restart...
Restarted application in 509ms.
Performing hot restart...
511ms
══╡ EXCEPTION CAUGHT BY ANIMATION LIBRARY
╞═════════════════════════════════════════════════════════
The following JSNoSuchMethodError was thrown
while notifying listeners for
AnimationController:
NoSuchMethodError: invalid member on null:      
'findRenderObject'
When the exception was thrown, this was the     
stack:
package:flutter/src/widgets/editable_text.dart  
1726:68            get renderEditable
package:flutter/src/widgets/editable_text.dart  
1590:20            [_onCursorColorTick]
package:flutter/src/animation/listener_helpers.dart 124:21        notifyListeners
package:flutter/src/animation/animation_controller.dart 362:5     set value
package:flutter/src/widgets/editable_text.dart
1625:37            [_cursorTick]
package:build_web_compilers/src/dev_compiler/dart_sdk.js 28721:9  <fn>
The AnimationController notifying listeners was:AnimationController#2e5b8(⏭ 1.000; paused)      
════════════════════════════════════════════════════════════════════════════════════════════════════
Another exception was thrown: NoSuchMethodError:invalid member on null: 'findRenderObject'      

Answer 1

"NoSuchMethodError 无效成员 on null"通常在您尝试调用 null 对象上的属性时抛出 - 可能是您正在使用的 Flutter Widget 上的错误。如前所述，应该已经推出了补丁。更新到最新版本的 Flutter SDK 应该可以解决这个问题。