import 'package:flutter/material.dart';

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

class MyWidget extends StatefulWidget {
  @override
  State<MyWidget> createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  bool _hideFlag = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Offstage(
                offstage: _hideFlag,
                child: FlutterLogo(
                  size: 200,
                ),
              ),
              ElevatedButton(
                onPressed: () => setState(() {
                  _hideFlag = !_hideFlag;
                }), 
                child: Text(_hideFlag ? '降ろした':'上がった'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}