Flutter Execute Method so long the button pressed

Question

I need to Execute Method when the user press buton and during this Pressing Operation in other words the user will press the button for unkown period of time ai need to execute method during this Period of time any one have an idea how i can do that in Flutter i tried GestureDetector but there are no Option to do that also onLongPress hasn't this option becouse on Long Press triggered after the press Operation I will write psudo code for what i need:

While(Button.isPressed){
 //Execute Method
 }

Answer 1

Use a Listener and a stateful widget. I also introduced a slight delay after every loop:

import 'dart:async';

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(brightness: Brightness.dark),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

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

  bool _buttonPressed = false;
  bool _loopActive = false;

  void _increaseCounterWhilePressed() async {
    // make sure that only one loop is active
    if (_loopActive) return;

    _loopActive = true;

    while (_buttonPressed) {
      // do your thing
      setState(() {
        _counter++;
      });

      // wait a bit
      await Future.delayed(Duration(milliseconds: 200));
    }

    _loopActive = false;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Center(
        child: Listener(
          onPointerDown: (details) {
            _buttonPressed = true;
            _increaseCounterWhilePressed();
          },
          onPointerUp: (details) {
            _buttonPressed = false;
          },
          child: Container(
            decoration: BoxDecoration(color: Colors.orange, border: Border.all()),
            padding: EdgeInsets.all(16.0),
            child: Text('Value: $_counter'),
          ),
        ),
      ),
    );
  }
}