如何在Flutter中将一个小部件置于另一个小部件之上？

import 'package:flutter/material.dart';

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Stack(
      children: <Widget>[
        // 在这里添加其他小部件
        Positioned(
          top: 50.0,
          left: 50.0,
          child: Container(
            width: 100.0,
            height: 100.0,
            color: Colors.blue,
          ),
        ),
      ],
    );
  }
}

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: MyWidget(),
      ),
    );
  }
}