solution4.dart

import 'package:flutter/material.dart';

void main() => runApp(
      MaterialApp(
        home: BallPage(),
      ),
    );

class BallPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.blue,
      appBar: AppBar(
        backgroundColor: Colors.blue.shade900,
        title: Text('Ask Me Anything'),
      ),
      body: Ball(),
    );
  }
}

class Ball extends StatefulWidget {
  @override
  _BallState createState() => _BallState();
}

class _BallState extends State<Ball> {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: FlatButton(
        onPressed: () {
          print('I got clicked');
        },
        child: Image.asset('images/ball1.png'),
      ),
    );
  }
}

This is how I got my code to work:

import 'package:flutter/material.dart';

void main() => runApp(
      MaterialApp(
        home: BallPage()
      ),
    );

class Ball extends StatefulWidget {
  const Ball({super.key});

  @override
  State<Ball> createState() => _BallState();
}

class _BallState extends State<Ball> {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: TextButton(
          onPressed: () {
              print('Button clicked!');
            },
          child: Image.asset('images/ball1.png'),
      )
    );
  }
}


class BallPage extends StatelessWidget {
  const BallPage({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.blue,
      appBar: AppBar(
        title: Text('Ask Me Anything',
          style: TextStyle(
              color: Colors.white
          ),
        ),
        backgroundColor: Colors.blue.shade900,
      ),
      body: Ball(),
    );
  }
}

Thank you @angelabauer

这是来自QQ邮箱的假期自动回复邮件。您好，已收到你的邮件，我将尽快回复，谢谢。