Flutter Layout Guide

Container

Container(
  color: Colors.cyanAccent,
  width: 80.0,
  height: 80.0,
 )

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      home: LayoutGuide(),
    );
  }
}

class LayoutGuide extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          color: Colors.cyanAccent,
          width: 80.0,
          height: 80.0,
        ),
      ),
    );
  }
}

Row

MainAxisAlignment

.center	.start	.end

.spaceEvenly	.spaceAround	.spaceBetween

CrossAxisAlignment

.center	.start	.end	.stretch

		Row(
          mainAxisAlignment: MainAxisAlignment.center,
          mainAxisSize: MainAxisSize.max,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            Container(
              color: Colors.cyanAccent,
              width: 80.0,
              height: 80.0,
            ),
            Container(
              color: Colors.blueAccent,
              width: 80.0,
              height: 80.0,
            ),
            Container(
              color: Colors.orangeAccent,
              width: 80.0,
              height: 80.0,
            ),
          ],
        )

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      home: LayoutGuide(),
    );
  }
}

class LayoutGuide extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          mainAxisSize: MainAxisSize.max,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            Container(
              color: Colors.cyanAccent,
              width: 80.0,
              height: 80.0,
            ),
            Container(
              color: Colors.blueAccent,
              width: 80.0,
              height: 80.0,
            ),
            Container(
              color: Colors.orangeAccent,
              width: 80.0,
              height: 80.0,
            ),
          ],
        ),
      ),
    );
  }
}