how to adjust size according to screen width in flutter code example

Example 1: flutter get width of screen

double height = MediaQuery.of(context).size.height;
double width = MediaQuery.of(context).size.width;

Example 2: how to give width based on screen size flutter

dependencies:
  flutter:
    sdk: flutter
  # add flutter_ScreenUtil
  flutter_screenutil: ^0.4.2