【 Flutter 】Flutter を 基礎 から 学習 ( ウィジェット編 ) part30 Single-child layout widgets

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

void main() {
  runApp(new MaterialApp(home: new MyApp()));
}

var ok = false;

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _State();
  }
}

class _State extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    var size = MediaQuery.of(context).size;
    var w = size.width;

    return MaterialApp(
        home: Scaffold(
      appBar: AppBar(
        title: Text('テスト中です。'),
      ),
      body: Column(children: <Widget>[
        Container(
          child: Text(w.toString()),
        ),
        Align(
            alignment: Alignment.centerRight,
            widthFactor: 4, // centerRightなので右側に埋まることはありません。
            child: SizedBox(
                width: 100,
                height: 100,
                child: DecoratedBox(
                  decoration: BoxDecoration(color: Colors.greenAccent),
                ))),
      ]),
    ));
  }
}