mediaquery_size.dart

import 'package:flutter/material.dart';

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

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

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    var x = MediaQuery.of(context).size.width;
    var y = MediaQuery.of(context).size.height;
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Container(
              height: y/2,
              width: x/2,
              child: Container(
                decoration: BoxDecoration(
                    color: Colors.green,
                    borderRadius: BorderRadius.all(Radius.circular(10.0))),
              ),
            ),
            Container(
              height: y,
              width: x/4,
              child: Container(
                decoration: BoxDecoration(
                    color: Colors.redAccent,
                    borderRadius: BorderRadius.all(Radius.circular(10.0))),
              ),
            ),
            Container(
              height: y/4,
              width: x/4,
              child: Container(
                decoration: BoxDecoration(
                    color: Colors.black,
                    borderRadius: BorderRadius.all(Radius.circular(10.0))),
              ),
            )
          ],
        ),
      ),
    );
  }
}