flutter_demo/lib/myself/my_home.dart

import 'package:flutter/material.dart';

class MyHomePage extends StatefulWidget {
  final String title;
  const MyHomePage({Key? key, required this.title}): super(key: key);

  @override
  _MyHomeState createState() => _MyHomeState();
}

class _MyHomeState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(title: Text(widget.title)),
      body: Text('$_counter'),
      floatingActionButton: FloatingActionButton(
          onPressed: _incrementCounter, 
          tooltip: 'Increment',
          child: Icon(Icons.add),
        ),
    );
  }
}