android - Flutter:未找到 MediaQuery 小部件祖先

Question

import 'package:flutter/material.dart';

void main() {
  runApp(Calculator());
}

class Calculator extends StatelessWidget {
  final numpad_background_color = Color(0x212121);
  final background_color = Colors.black;
  final equal_button_background_color = Color(0xffbe00);

  final textColor = Colors.white;
  final operatorTextColor = Color(0xf3ba0e);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            appBar: appbar(context),
            body: Stack(
              children: [Container(height: MediaQuery.of(context).size.height * 0.37), numpad(context)],
            )));
  }

  Widget appbar(BuildContext context) {
    return AppBar(title: Text("Rechner", style: TextStyle(color: textColor, fontSize: 15)), backgroundColor: background_color, leading: Icon(Icons.history));
  }

  Widget numpad(BuildContext context) {
    return Container(decoration: BoxDecoration(borderRadius: BorderRadius.circular(5), color: numpad_background_color), child:
      Column(children: [

      ],),);
  }
}

Error: No MediaQuery ancestor could be found starting from the context that was passed to MediaQuery.of(). This can happen because you have not added a WidgetsApp, CupertinoApp, or MaterialApp widget (those widgets introduce a MediaQuery), or it can happen if the context you use comes from a widget above those widgets.

我不明白这个错误，我创建了一个 MaterialApp Widget 并从那里调用 MediaQuery，为什么会出现这个错误？

Answer 1

尝试创建另一个像这样的小部件

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Calculator(),
    );
  }
}

然后您的主要方法将如下所示

void main() {
  runApp(MyApp());
}