如何更改CupertinoAlertDialog的背景色？

import 'package:flutter/cupertino.dart';
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('CupertinoAlertDialog Background Color')),
        body: Center(child: Builder(builder: (context) {
          return ElevatedButton(
            onPressed: () {
              showDialog(
                context: context,
                builder: (BuildContext context) {
                  return CupertinoAlertDialog(
                    title: Text('Custom Background Color'),
                    content: Container(
                      decoration: BoxDecoration(
                        color: Colors.yellow, // 设置背景色
                        borderRadius: BorderRadius.circular(12),
                      ),
                      padding: EdgeInsets.all(16),
                      child: Text('This is a custom background color dialog.'),
                    ),
                    actions: <Widget>[
                      CupertinoDialogAction(
                        child: Text('OK'),
                        onPressed: () {
                          Navigator.of(context).pop();
                        },
                      ),
                    ],
                  );
                },
              );
            },
            child: Text('Show Dialog'),
          );
        })),
      ),
    );
  }
}