缩放布局组件FittedBox主要有两个功能：缩放和位置调整。FittedBox会根据自己的尺寸来调整child的尺寸。

使用FittedBox需要用到两个常用的属性，fit缩放方式，跟前面学到的Image组件的填充方式一致，其次就是alignment对齐方式。

import 'package:flutter/material.dart';

class DemoFittedBox extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Container(
          width: 50.0,
          height: 50.0,
          color: Colors.blue,
          child: FittedBox(
            child: Text('缩放组件'),
          ),
        ),
        Divider(),
        Container(
          width: 100.0,
          height: 100.0,
          color: Colors.blue,
          child: FittedBox(
            child: Text('缩放组件'),
          ),
        ),
        Divider(),
        Container(
          width: 50.0,
          height: 50.0,
          color: Colors.blue,
          child: FittedBox(
            fit: BoxFit.cover,
            child: Text('缩放组件'),
          ),
        ),
        Divider(),
        Container(
          width: 50.0,
          height: 50.0,
          color: Colors.blue,
          child: FittedBox(
            fit: BoxFit.fitWidth,
            child: Text('缩放组件'),
          ),
        ),
        Divider(),
        Container(
          width: 50.0,
          height: 50.0,
          color: Colors.blue,
          child: FittedBox(
            fit: BoxFit.contain,
            child: Text('缩放组件'),
          ),
        ),
        Divider(),
        Container(
          width: 50.0,
          height: 50.0,
          color: Colors.blue,
          child: FittedBox(
            fit: BoxFit.scaleDown,
            alignment: Alignment.bottomCenter,
            child: Text('缩放组件'),
          ),
        ),
      ],
    );
  }
}