App_Flutter/lib/utils/size_fit.dart

import 'package:flutter/material.dart';

extension IntFit on int{
  double get px {
    return SizeFit.setPx(toDouble());
  }

  double get rpx {
    return SizeFit.setRpx(toDouble());
  }
}

extension DoubleFit on double{
  double get px{
    return SizeFit.setPx(this);
  }

  double get rpx {
    return SizeFit.setRpx(this);
  }
}

class SizeFit {
  static MediaQueryData? _mediaQueryData;
  static double? screenWidth,screenHeight,rpx,px;
  static void initialize(BuildContext context,{double standardWidth = 750}){
    _mediaQueryData = MediaQuery.of(context);
    screenWidth = _mediaQueryData!.size.width;
    screenHeight = _mediaQueryData!.size.height;
    rpx = screenWidth!/standardWidth;
    px = screenWidth!/standardWidth*2;
  }

  static double setPx(double size){
    return SizeFit.rpx!*size*2;
  }

  static double setRpx(double size){
    return SizeFit.px!*size/2;
  }
}