Flutter 颤振中的小部件库错误捕获异常

我有这个应用程序在颤振。它有两个类用来生成注释列表

这是主类MyApp类：

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:notesgenerator/sala.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override

  Widget build(BuildContext context) {

    List<Sala> locs = [
      Sala(note: 'Study', noteDes: 'from 6pm ~ 8pm'),
      Sala(note: 'Work', noteDes: 'from 8pm ~ 9pm'),
      Sala(note: 'Play', noteDes: 'from 9pm ~ 9:30pm'),
      Sala(note: 'Eat', noteDes: 'from 9:30pm ~ 10pm'),
    ];

    return Scaffold(
      appBar: AppBar(
        title: Text('NoteIndex'),
        centerTitle: true,
      ),
      body: ListView.builder(
          itemCount: 10,
          itemBuilder: (context, index) {
            return Card(
              child: ListTile(
                onTap: () {},
                title: (Text(locs[index].note)),
              ),
            );
          }),
    );}}

当我尝试运行它时，我得到以下结果：

I/flutter (21388): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (21388): The following assertion was thrown building MyApp:
I/flutter (21388): MediaQuery.of() called with a context that does not contain a MediaQuery.
I/flutter (21388): No MediaQuery ancestor could be found starting from the context that was passed to MediaQuery.of().
I/flutter (21388): This can happen because you do not have a WidgetsApp or MaterialApp widget (those widgets introduce
I/flutter (21388): a MediaQuery), or it can happen if the context you use comes from a widget above those widgets.
I/flutter (21388): The context used was:
I/flutter (21388):   Scaffold
I/flutter (21388): 
I/flutter (21388): The relevant error-causing widget was:
I/flutter (21388):   MyApp file:///F:/FlutterProjects/notesgenerator/lib/main.dart:6:23
I/flutter (21388): 
I/flutter (21388): When the exception was thrown, this was the stack:
I/flutter (21388): #0      MediaQuery.of (package:flutter/src/widgets/media_query.dart:798:5)
I/flutter (21388): #1      ScaffoldState.didChangeDependencies (package:flutter/src/material/scaffold.dart:1993:50)
I/flutter (21388): #2      StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4376:12)
I/flutter (21388): #3      ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
I/flutter (21388): #4      Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter (21388): #5      Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter (21388): #6      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16)
I/flutter (21388): #7      Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5)
I/flutter (21388): #8      ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4206:5)
I/flutter (21388): #9      ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
I/flutter (21388): #10     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter (21388): #11     Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter (21388): #12     RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:1028:16)
I/flutter (21388): #13     RenderObjectToWidgetElement.mount (package:flutter/src/widgets/binding.dart:999:5)
I/flutter (21388): #14     RenderObjectToWidgetAdapter.attachToRenderTree.<anonymous closure> (package:flutter/src/widgets/binding.dart:942:17)
I/flutter (21388): #15     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2412:19)
I/flutter (21388): #16     RenderObjectToWidgetAdapter.attachToRenderTree (package:flutter/src/widgets/binding.dart:941:13)
I/flutter (21388): #17     WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:819:7)
I/flutter (21388): #18     WidgetsBinding.scheduleAttachRootWidget.<anonymous closure> (package:flutter/src/widgets/binding.dart:804:7)
I/flutter (21388): #27     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:384:19)
I/flutter (21388): #28     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:418:5)
I/flutter (21388): #29     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:174:12)
I/flutter (21388): (elided 8 frames from package dart:async and package dart:async-patch)
I/flutter (21388): 
I/flutter (21388): ════════════════════════════════════════════════════════════════════════════════════════════════════

I/颤振（21388）：══╡ WIDGETS库捕获到异常╞═══════════════════════════════════════════════════════════
I/flatter（21388）：在构建MyApp时抛出以下断言：
I/flatter（21388）：使用不包含MediaQuery的上下文调用MediaQuery.of（）。
I/flatter（21388）：从传递给MediaQuery.of（）的上下文开始，找不到MediaQuery祖先。
I/flatter（21388）：这可能是因为您没有WidgetsApp或MaterialApp小部件（这些小部件引入
I/flatter（21388）：一个MediaQuery），或者如果您使用的上下文来自这些小部件之上的小部件，则可能会发生这种情况。
I/颤振（21388）：使用的上下文是：
I/颤振（21388）：脚手架
I/颤振（21388）：
I/flatter（21388）：导致错误的相关小部件是：
I/颤振（21388）：MyAppfile:///F:/FlutterProjects/notesgenerator/lib/main.dart:6:23
I/颤振（21388）：
I/flatter（21388）：当抛出异常时，这是堆栈：
I/flatter（21388）：#0 MediaQuery.of（包：flatter/src/widgets/media_query.dart:798:5）
I/颤振（21388）：#1 ScaffoldState.didChangeDependencies（包装：颤振/src/material/scaffold.dart:1993:50）
I/flatter（21388）：#2 StatefulElement._firstBuild（包：flatter/src/widgets/framework.dart:4376:12）
I/flatter（21388）：#3 ComponentElement.mount（包：flatter/src/widgets/framework.dart:4201:5）
I/flatter（21388）：#4 Element.inflateWidget（包：flatter/src/widgets/framework.dart:3194:14）
I/flatter（21388）：#5 Element.updateChild（包：flatter/src/widgets/framework.dart:2988:12）
I/flatter（21388）：#6 ComponentElement.performRebuild（包：flatter/src/widgets/framework.dart:4243:16）
I/flatter（21388）：#7 Element.rebuild（包：flatter/src/widgets/framework.dart:3947:5）
I/flatter（21388）：#8个组件元素。firstBuild（包：flatter/src/widgets/framework.dart:4206:5）
I/flatter（21388）：#9 ComponentElement.mount（包：flatter/src/widgets/framework.dart:4201:5）
I/flatter（21388）：#10 Element.inflateWidget（包：flatter/src/widgets/framework.dart:3194:14）
I/flatter（21388）：#11 Element.updateChild（包：flatter/src/widgets/framework.dart:2988:12）
I/flatter（21388）：#12 RenderObjectToWidgetElement._重建（包：flatter/src/widgets/binding.dart:1028:16）
I/flatter（21388）：#13 RenderObjectToWidgetElement.mount（包：flatter/src/widgets/binding.dart:999:5）
I/颤振（21388）：#14 RenderObjectToWidgetAdapter.attachToRenderTree。（包：flatter/src/widgets/binding.dart:942:17）
I/flatter（21388）：#15 BuildOwner.buildScope（包：flatter/src/widgets/framework.dart:2412:19）
I/flatter（21388）：#16 RenderObjectToWidgetAdapter.attachToRenderTree（包：flatter/src/widgets/binding.dart:941:13）
I/flatter（21388）：#17 WidgetsBinding.attachRootWidget（包：flatter/src/widgets/binding.dart:819:7）
I/flatter（21388）：#18 WidgetsBinding.scheduleAttachRootWidget。（包：flatter/src/widgets/binding.dart:804:7）
I/flatter（21388）：#27 _计时器。_运行计时器（dart:isolate patch/Timer_impl.dart:384:19）
I/flatter（21388）：#28 _Timer._handleMessage（dart:隔离补丁/定时器_impact.dart:418:5）
I/flatter（21388）：#29 RawReceivePortImpl.handleMessage（dart:isolate patch/isolate_patch.dart:174:12）
I/flatter（21388）：（从包dart:async和包dart:async补丁中删除8帧）
I/颤振（21388）：
I/颤振（21388）：════════════════════════════════════════════════════════════════════════════════════════════════════

---

如果你能帮忙，我会非常感激的！如果您有任何问题，请在评论中告诉我

你需要用塑料包裹你的脚手架

MaterialApp（）

因为这是引入MediaQuery的小部件

MyApp版本中的更改：

    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: Scaffold(
       ...
      ),
    );

---

用聚丙烯材料包裹你的脚手架

    return MaterialApp(
  title: 'Flutter Demo',
  theme: ThemeData(
    primarySwatch: Colors.blue,
    visualDensity: VisualDensity.adaptivePlatformDensity,
  ),
  home: Scaffold(),
);

---

你的代码格式不好，这是不可编辑的，因为正如stackoverflow指南提到的，你应该解释你的问题，给出你没有做的例子和上下文。请告诉我们细节。

    return MaterialApp(
  title: 'Flutter Demo',
  theme: ThemeData(
    primarySwatch: Colors.blue,
    visualDensity: VisualDensity.adaptivePlatformDensity,
  ),
  home: Scaffold(),
);