How To Use Column Widget Using Flutter Android App

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}
class MyHomePage extends StatefulWidget {
  final String title;
  MyHomePage({this.title});
  @override
  _MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage>{
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.black,
      appBar: AppBar(
          title: Text("Column Widget")),
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.max,
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            Container(
              height: 50.0,
              width: 50.0,
              color: Colors.green,
            ),
            Container(
              height: 50.0,
              width: 50.0,
              color: Colors.pink,
            ),
            Container(
              height: 50.0,
              width: 50.0,
              color: Colors.yellow,
            )
          ],
        ),
      ),
    );
  }
}