使用不包含MediaQuery的上下文(从MaterialApp)调用MediaQuery.of()

import 'package:flutter/material.dart';

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

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

class MediaQueryExample extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('MediaQuery Example'),
      ),
      body: Center(
        child: Container(
          child: Text(
            'Screen Width: ${MediaQuery.of(context).size.width}',
            style: TextStyle(fontSize: 20),
          ),
        ),
      ),
    );
  }
}