How To Add Device Screen Height&Width In Flutter App

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
        home: Scaffold(
          appBar: AppBar(
            centerTitle: true,
            backgroundColor: Colors.deepPurple[400],
            title: Text("Device Height Width Dynamically"),
          ),
            body: Center(
                child: GetDimension()
            )
        )
    );
  }
}

class GetDimension extends StatefulWidget {

  GetDimensionState createState() => GetDimensionState();

}

class GetDimensionState extends State {

  double heightHolder = 0.0 ;
  double widthHolder = 0.0 ;

  getHeightWidth(context){

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

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

    setState(() {
      heightHolder = height.roundToDouble();
      widthHolder = width.roundToDouble() ;
    });

  }

  @override
  Widget build(BuildContext context) {

    return Scaffold(
        body: Center(child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(
                  padding: EdgeInsets.fromLTRB(0, 20, 0, 10),
                  child: Text('Height = '+'$heightHolder',
                      style: TextStyle(fontSize: 21))),

              Container(
                  padding: EdgeInsets.fromLTRB(0, 10, 0, 10),
                  child: Text('Width = '+'$widthHolder',
                      style: TextStyle(fontSize: 21))),

              RaisedButton(
                onPressed: () => getHeightWidth(context),
                child: Text('Get Device Height Width Dynamically'),
                textColor: Colors.white,
                color: Colors.deepPurple[400],
                padding: EdgeInsets.fromLTRB(10, 10, 10, 10),
              )

            ]))
    );
  }
}