import 'package:flutter/material.dart';

import 'dart:ui';

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

class MyWidget extends StatefulWidget {
  MyWidget();

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

class _MyWidgetState extends State<MyWidget> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Stack(
          children: <Widget>[
            Text(
              '見えますか' * 500,
              style: TextStyle(
                color: Colors.blue,
                fontSize: 24,
                fontWeight: FontWeight.bold,
              ),
            ),
            Center(
              child: BackdropFilter(
                filter: ImageFilter.blur(
                  sigmaX: 4,
                  sigmaY: 5,
                ),
                child: SizedBox(
                  width: 500,
                  height: 250,
                  child: Text(
                    'これ見える：$_counter',
                    style: Theme.of(context).textTheme.headline3,
                  ),
                ),
              ),
            )
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'プラス',
        child: Icon(Icons.add),
      ),
    );
  }
}