Container包含Container出现的问题。

main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  Widget build(BuildContext context) {

    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: new Center(
        child: new Column(
          children: <Widget>[
            Container(
              margin: EdgeInsets.only(top: 10),
              width: 200,
              height: 200,
              decoration: BoxDecoration(
                  border: Border.all(color: Colors.orange[400], width: 0.5),
                  borderRadius: BorderRadius.circular(6),
                  color: Colors.orange[100]),
              
              child: Container(
                margin: EdgeInsets.only(top: 10),
                width: 50,
                height: 50,
                decoration: BoxDecoration(
                    borderRadius: BorderRadius.circular(6),
                    color: Colors.orange),
                child: Text('22'),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

我想实现这个效果