https://stackoverflow.com/questions/49704497/how-to-make-flutter-app-responsive-according-to-different-screen-size

https://jaycoding.tech/tutorials/guides/how-to-create-a-responsive-app-in-flutte-xmafdg

在实际的使用中，会用到flutter_screenutil 第三方插件,使用方法为

首先,在pubspec.yaml 中加入依赖：

flutter_screenutil: ^5.0.0+2

其次,在main.dart文件中加入以下代码

ScreenUtilInit( // New Widget Here!!
  designSize: Size(325, 667), // Design Size
  child: MaterialApp(
    title: 'Flutter Demo',
    theme: ThemeData(
      primarySwatch: Colors.blue,
      visualDensity: VisualDensity.adaptivePlatformDensity,
    ),
    home: MyHomePage(title: 'Flutter Demo Home Page'),
  ),
);

后面和大小和高度有关的可以用以下的写法：

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    //Set the fit size (fill in the screen size of the device in the design) If the design is based on the size of the iPhone6 ​​(iPhone6 ​​750*1334)
    return ScreenUtilInit(
      designSize: Size(360, 690),
      builder: () => MaterialApp(
        debugShowCheckedModeBanner: false,
        title: 'Flutter_ScreenUtil',
        theme: ThemeData(
          primarySwatch: Colors.blue,
          textTheme: TextTheme(button: TextStyle(fontSize: 45.sp)),
        ),
        builder: (context, widget) {
          return MediaQuery(
            //Setting font does not change with system font size
            data: MediaQuery.of(context).copyWith(textScaleFactor: 1.0),
            child: widget,
          );
        },
        home: HomePage(title: 'FlutterScreenUtil Demo'),
      ),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    printScreenInformation();
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: SingleChildScrollView(
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Row(
              children: <Widget>[
                // Using Extensions
                Container(
                  padding: EdgeInsets.all(10.w),
                  width: 0.5.sw,
                  height: 200.h,
                  color: Colors.red,
                  child: Text(
                    'My actual width: ${0.5.sw}dp \n\n'
                    'My actual height: ${200.h}dp',
                    style: TextStyle(
                      color: Colors.white,
                      fontSize: 12.sp,
                    ),
                  ),
                ),
                // Without using Extensions
                Container(
                  padding: EdgeInsets.all(ScreenUtil().setWidth(10)),
                  width: 180.w,
                  height: 200.h,
                  color: Colors.blue,
                  child: Text(
                    'My design draft width: 180dp\n\n'
                    'My design draft height: 200dp',
                    style: TextStyle(
                      color: Colors.white,
                      fontSize: 16.sp,
                    ),
                  ),
                ),
              ],
            ),
            Container(
              padding: EdgeInsets.all(ScreenUtil().setWidth(10)),
              width: 100.r,
              height: 100.r,
              color: Colors.green,
              child: Text(
                'I am a square with a side length of 100',
                style: TextStyle(
                  color: Colors.white,
                  fontSize: ScreenUtil().setSp(12),
                ),
              ),
            ),
            Text('Device width:${ScreenUtil().screenWidth}dp'),
            Text('Device height:${ScreenUtil().screenHeight}dp'),
            Text('Device pixel density:${ScreenUtil().pixelRatio}'),
            Text('Bottom safe zone distance:${ScreenUtil().bottomBarHeight}dp'),
            Text('Status bar height:${ScreenUtil().statusBarHeight}dp'),
            Text(
              'The ratio of actual width to UI design:${ScreenUtil().scaleWidth}',
              textAlign: TextAlign.center,
            ),
            Text(
              'The ratio of actual height to UI design:${ScreenUtil().scaleHeight}',
              textAlign: TextAlign.center,
            ),
            SizedBox(
              height: 10.h,
            ),
            Text('System font scaling factor:${ScreenUtil().textScaleFactor}'),
            SizedBox(height: 5),
            Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                Text(
                  '16sp, will not change with the system.',
                  style: TextStyle(
                    color: Colors.black,
                    fontSize: 16.sp,
                  ),
                  textScaleFactor: 1.0,
                ),
                Text(
                  '16sp,if data is not set in MediaQuery,my font size will change with the system.',
                  style: TextStyle(
                    color: Colors.black,
                    fontSize: 16.sp,
                  ),
                ),
              ],
            )
          ],
        ),
      ),
    );
  }

  void printScreenInformation() {
    print('Device width dp:${1.sw}dp');
    print('Device height dp:${1.sh}dp');
    print('Device pixel density:${ScreenUtil().pixelRatio}');
    print('Bottom safe zone distance dp:${ScreenUtil().bottomBarHeight}dp');
    print('Status bar height dp:${ScreenUtil().statusBarHeight}dp');
    print('The ratio of actual width to UI design:${ScreenUtil().scaleWidth}');
    print(
        'The ratio of actual height to UI design:${ScreenUtil().scaleHeight}');
    print('System font scaling:${ScreenUtil().textScaleFactor}');
    print('0.5 times the screen width:${0.5.sw}dp');
    print('0.5 times the screen height:${0.5.sh}dp');
    print('Screen orientation:${ScreenUtil().orientation}');
  }
}