const Align({
    Key key,
    this.alignment = Alignment.center,
    this.widthFactor,
    this.heightFactor,
    Widget child
  })

import 'package:flutter/material.dart';

void main() => runApp(
  MaterialApp(
    title: '圖標(biāo)按鈕組件示例',
    home: LayoutDemo(),
  ),
);

class LayoutDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('圖標(biāo)按鈕組件示例'),
      ),
      body: Align(
        alignment: Alignment.centerLeft,
        widthFactor: 2.0,
        heightFactor: 2.0,
        //添加圖標(biāo)按鈕
        child: IconButton(
          //圖標(biāo)元素
          icon: Icon(Icons.volume_up,size: 48.0,),
          //按鈕提示
          tooltip: '按下操作',
          //按下事件響應(yīng)
          onPressed:(){
            print('按下操作');
          },
        ),
      ),
    );
  }
}