title: LateInitializationError: Field 'screenWidth' has not been initialized. Exception in flutter
body: <p>I am new to flutter
  I had this size config file and I used it in an old project
  and right now I took it again to another project and it shows no errors but when I run it gives me an Exception :
  ════════ Exception caught by widgets library ═══════════════════════════════════
  The following LateError was thrown building Body(dirty):
  LateInitializationError: Field 'screenWidth' has not been initialized.</p>
  <pre><code>import 'package:flutter/material.dart';
  
  
  class SizeConfig {
    static late MediaQueryData _mediaQueryData;
    static late double screenWidth;
    static late double screenHeight;
    static double? defaultSize;
    static Orientation? orientation;
    void init(BuildContext context) {
      _mediaQueryData = MediaQuery.of(context);
      screenWidth = _mediaQueryData.size.width;
      screenHeight = _mediaQueryData.size.height;
      orientation = _mediaQueryData.orientation;
    }
  }
  // Get the proportionate height as per screen size
  double getProportionateScreenHeight(double inputHeight) {
    double screenHeight = SizeConfig.screenHeight;
    // 812 is the layout height that designer use
    return (inputHeight / 812.0) * screenHeight;
  }
  // Get the proportionate height as per screen size
  double getProportionateScreenWidth(double inputWidth) {
    double screenWidth = SizeConfig.screenWidth;
    // 375 is the layout width that designer use
    return (inputWidth / 375.0) * screenWidth;
  }
  </code></pre>