【Flutter】ボタン長押し処理の基本から長押し処理時の状態管理までの完全ガイド！

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: LongPressDemo(),
        ),
      ),
    );
  }
}

class LongPressDemo extends StatefulWidget {
  @override
  _LongPressDemoState createState() => _LongPressDemoState();
}

class _LongPressDemoState extends State<LongPressDemo> {
  int _counter = 0;

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

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onLongPress: () {
        _incrementCounter();
      },
      child: Container(
        padding: EdgeInsets.all(12.0),
        decoration: BoxDecoration(
          color: Colors.blue,
          borderRadius: BorderRadius.circular(8.0),
        ),
        child: Text(
          '長押しでカウントアップ: $_counter',
          style: TextStyle(fontSize: 20, color: Colors.white),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'dart:async';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: LongPressAfterDelayDemo(),
        ),
      ),
    );
  }
}

class LongPressAfterDelayDemo extends StatefulWidget {
  @override
  _LongPressAfterDelayDemoState createState() => _LongPressAfterDelayDemoState();
}

class _LongPressAfterDelayDemoState extends State<LongPressAfterDelayDemo> {
  int _counter = 0;
  Timer? _timer;

  void _startIncrementCounterAfterDelay() {
    _timer = Timer(Duration(seconds: 2), () {
      setState(() {
        _counter++;
      });
    });
  }

  @override
  void dispose() {
    _timer?.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onLongPress: () {
        _startIncrementCounterAfterDelay();
      },
      child: Container(
        padding: EdgeInsets.all(12.0),
        decoration: BoxDecoration(
          color: Colors.green,
          borderRadius: BorderRadius.circular(8.0),
        ),
        child: Text(
          '2秒後に長押しでカウントアップ: $_counter',
          style: TextStyle(fontSize: 20, color: Colors.white),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'dart:async';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: ContinuousLongPressDemo(),
        ),
      ),
    );
  }
}

class ContinuousLongPressDemo extends StatefulWidget {
  @override
  _ContinuousLongPressDemoState createState() => _ContinuousLongPressDemoState();
}

class _ContinuousLongPressDemoState extends State<ContinuousLongPressDemo> {
  int _counter = 0;
  Timer? _timer;

  void _startContinuousIncrement() {
    _timer = Timer.periodic(Duration(milliseconds: 200), (timer) {
      setState(() {
        _counter++;
      });
    });
  }

  void _stopContinuousIncrement() {
    _timer?.cancel();
  }

  @override
  void dispose() {
    _timer?.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onLongPressStart: (details) {
        _startContinuousIncrement();
      },
      onLongPressEnd: (details) {
        _stopContinuousIncrement();
      },
      child: Container(
        padding: EdgeInsets.all(12.0),
        decoration: BoxDecoration(
          color: Colors.red,
          borderRadius: BorderRadius.circular(8.0),
        ),
        child: Text(
          '長押しで連続カウント: $_counter',
          style: TextStyle(fontSize: 20, color: Colors.white),
        ),
      ),
    );
  }
}