堆栈边框上的flutter place构件

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Stack and Positioned Example')),
        body: Center(
          child: Container(
            width: 300,
            height: 300,
            decoration: BoxDecoration(
              border: Border.all(color: Colors.black, width: 2),
            ),
            child: Stack(
              children: [
                Positioned(
                  top: 50,
                  left: 50,
                  child: Container(
                    width: 100,
                    height: 100,
                    color: Colors.red,
                  ),
                ),
                Positioned(
                  bottom: 50,
                  right: 50,
                  child: Container(
                    width: 100,
                    height: 100,
                    color: Colors.blue,
                  ),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}