flutter 写一个screen_util类，目的是适配屏幕，支持px和rpx

好的，以下是一个支持 px 和 rpx 的 ScreenUtil 类，可以用于 Flutter 屏幕适配：

import 'package:flutter/material.dart';

class ScreenUtil {
  static late double _screenWidth;
  static late double _screenHeight;
  static late double _pixelRatio;
  static late double _statusBarHeight;
  static late double _bottomBarHeight;
  static late double _textScaleFactor;

  static void init(BuildContext context) {
    MediaQueryData mediaQuery = MediaQuery.of(context);
    _screenWidth = mediaQuery.size.width;
    _screenHeight = mediaQuery.size.height;
    _pixelRatio = mediaQuery.devicePixelRatio;
    _statusBarHeight = mediaQuery.padding.top;
    _bottomBarHeight = mediaQuery.padding.bottom;
    _textScaleFactor = mediaQuery.textScaleFactor;
  }

  static double get screenWidth => _screenWidth;

  static double get screenHeight => _screenHeight;

  static double get pixelRatio => _pixelRatio;

  static double get statusBarHeight => _statusBarHeight;

  static double get bottomBarHeight => _bottomBarHeight;

  static double get textScaleFactor => _textScaleFactor;

  static double setWidth(double widthPx) => widthPx * _screenWidth / 750;

  static double setHeight(double heightPx) => heightPx * _screenHeight / 1334;

  static double setSp(double fontSizePx) => fontSizePx * _textScaleFactor;

  static double setBorderRadius(double radiusPx) => radiusPx * _pixelRatio;

  static double setRpx(double rpx) => rpx * _screenWidth / 750;
}

使用方法：

在 MaterialApp 的 build 方法中调用 ScreenUtil.init(context)，初始化 ScreenUtil 类。

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    ScreenUtil.init(context);
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

在布局中使用 ScreenUtil.setWidth、ScreenUtil.setHeight、ScreenUtil.setSp 和 ScreenUtil.setRpx 方法来适配宽度、高度、字体大小和 rpx。

Container(
  width: ScreenUtil.setWidth(100),
  height: ScreenUtil.setHeight(100),
  margin: EdgeInsets.only(top: ScreenUtil.setHeight(20)),
  padding: EdgeInsets.symmetric(horizontal: ScreenUtil.setWidth(20)),
  decoration: BoxDecoration(
    borderRadius: BorderRadius.circular(ScreenUtil.setBorderRadius(10)),
    color: Colors.grey[200],
  ),
  child: Text(
    'Hello, World!',
    style: TextStyle(fontSize: ScreenUtil.setSp(32)),
  ),
),

其中，setWidth 和 setHeight 方法用于适配宽度和高度，参数单位为 px；setSp 方法用于适配字体大小，参数单位为 px；setBorderRadius 方法用于适配边框半径，参数单位为 px；setRpx 方法用于适配 rpx，即屏幕宽度的 1/750，参数单位为 rpx。