如何使用Flutter将窗体居中对齐？

import 'package:flutter/material.dart';

class MyCenteredForm extends StatefulWidget {
  @override
  _MyCenteredFormState createState() => _MyCenteredFormState();
}

class _MyCenteredFormState extends State<MyCenteredForm> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Centered Form'),
      ),
      body: Center(
        child: Container(
          width: 300, // 设置窗体宽度
          height: 200, // 设置窗体高度
          child: Form(
            // 在这里添加表单内容
          ),
        ),
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: MyCenteredForm(),
  ));
}