有没有办法在Flutter中的应用栏操作按钮后面添加阴影？

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('Flutter App'),
          actions: [
            IconButton(
              icon: Icon(Icons.settings),
              onPressed: () {},
            ),
          ],
        ),
        body: Container(
          child: Stack(
            children: [
              Container(
                height: kToolbarHeight,
                decoration: BoxDecoration(
                  color: Colors.white,
                  boxShadow: [
                    BoxShadow(
                      color: Colors.grey.withOpacity(0.5),
                      spreadRadius: 2,
                      blurRadius: 5,
                      offset: Offset(0, 3),
                    ),
                  ],
                ),
              ),
              Positioned(
                top: 0,
                left: 0,
                right: 0,
                child: AppBar(
                  title: Text('Flutter App'),
                  actions: [
                    IconButton(
                      icon: Icon(Icons.settings),
                      onPressed: () {},
                    ),
                  ],
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}