如何在按下flatButton后在“文本”小工具中显示文本？

import 'package:flutter/material.dart';

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

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

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String displayText = '';

  void updateText() {
    setState(() {
      displayText = 'Hello, World!';
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('FlatButton Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(
              displayText,
              style: TextStyle(fontSize: 20),
            ),
            SizedBox(height: 20),
            FlatButton(
              onPressed: updateText,
              child: Text('Press Me'),
              color: Colors.blue,
              textColor: Colors.white,
            ),
          ],
        ),
      ),
    );
  }
}