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Accepted
Anton
Asked:2020-05-12 21:14:18 +0000 UTC2020-05-12 21:14:18 +0000 UTC

MediaQuery.of(context) 不工作

  • 772

不工作，错误

宽度：MediaQuery.of(context).size.width / 2，高度：MediaQuery.of(context).size.height / 2，

不起作用，只能显示值

宽度：window.physicalSize.width / 2，高度：window.physicalSize.height / 2，

主要.dart

import 'package:flutter/material.dart';
import 'dart:ui';

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

class MyApp extends StatefulWidget {
 @override
 _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
 //объявление переменных

 //вызывается один раз при инициализации виджета
 @override
 void initState() {
  super.initState();

 }

 void _f1(double value) {
  setState(() {

  });
 }

 @override
 Widget build(BuildContext context) {
  return MaterialApp(
   debugShowCheckedModeBanner: false,
   title: 'Name App',
   theme: ThemeData(
    primarySwatch: Colors.blue,
   ),
   home: Scaffold(
    appBar: AppBar(
     title: Text('Name Page'),
    ),
    body: Stack(
     children: <Widget>[
      Align(
       alignment: Alignment.center,
       child: Container(

        //НЕ РАБОТАЕТ, ОШИБКА
        //width: MediaQuery.of(context).size.width / 2,
        //height: MediaQuery.of(context).size.height / 2,

        //НЕ РАБОТАЕТ, МОЖНО ТОЛЬКО ВЫВЕСТИ НА ЭКРАН ЗНАЧЕНИЯ
        width: window.physicalSize.width / 2,
        height: window.physicalSize.height / 2,

        color: Colors.pink,
       ),
      ),
     ],
    ),
   ),
  );
 }
}

如果有人遇到此错误，请告诉我。谢谢你。在此处输入图像描述

flutter

1 个回答

  1. Best Answer

    好吧，当然，如果你的小部件没有正确构建，它就不能正常工作（window.physicalSize它只是用来找出屏幕的物理尺寸，不应该随意使用）：

    import 'package:flutter/material.dart';

void main() async {
  runApp(App());
}

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Name App',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: Text('Name Page'),
        ),
        body: MyApp(),
      ),
    );
  }
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return Stack(
      children: <Widget>[
        Align(
          alignment: Alignment.center,
          child: Container(
            width: MediaQuery.of(context).size.width / 2,
            height: MediaQuery.of(context).size.height / 2,
            color: Colors.pink,
          ),
        ),
      ],
    );
  }
}
    • 1

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