How to use Column widget in Flutter

In this Google flutter code example we are going to learn how to Column widget in Flutter.

You can copy and adopt this source code example to your android project without reinventing the wheel.

The comments on the code provide more detailed explanation

The code is based on flutter version 1.

main.dart (App entry point)

import 'package:flutter/material.dart';
import 'column.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Baseline Widget',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: BasicColumn(),
    );
  }
}

column.dart

import 'package:flutter/material.dart';

class BasicColumn extends StatelessWidget {
  //A widget that displays its children in a vertical array.
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Column Widget")),
      body: Center(
        child: Column(
          //set maxAxisSize to determine how much space should be occupied in the main axis, here, the vertical axis
          mainAxisSize: MainAxisSize.max,
          //set mainAxisAlignment: How the children should be placed along the main axis, here, the vertical axis
          //MainAxisAlignment.spaceAround: Place the free space evenly between the children as well as half of that space before and after the first and last child.
          //MainAxisAlignment.center: Place the children as close to the middle of the main axis as possible
          //MainAxisAlignment.spaceBetween: Place the free space evenly between the children
          //MainAxisAlignment.start: Place the children as close to the start of the main axis as possible
          //MainAxisAlignment.end: Place the children as close to the end of the main axis as possible.
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          //set how the widgets should be placed in the opposing axis (horizontal), same as MainAxisAlignment
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            Container(
              height: 50.0,
              width: 50.0,
              color: Colors.red,
            ),
            Container(
              height: 50.0,
              width: 50.0,
              color: Colors.blue,
            ),
            Container(
              height: 50.0,
              width: 50.0,
              color: Colors.brown,
            )
          ],
        ),
      ),
    );
  }
}

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