long press for incrementing value - flutter

Question

I have an increment button with a callback function:
class IncrementButton extends StatelessWidget {
final VoidCallback callback;
const IncrementButton({
Key? key,
required this.callback,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return GestureDetector(
onTap: () {
callback();
},
onLongPressStart: ((details) {
callback();
}),
......
);
}
}
And using it as:
IncrementButton(
callback: _increment,
),
The _increment function is as:
_increment() {
value += 1;
}
What I want is when the user taps once, the _increment function will be called. But when the user keeps a long press on the button, the same increment function should be called. But that doesn't happen. The _increment method is getting called only once for long Press

Answer 1

I guess you want the number to be incremented continually while long pressing the button/container. You need a timer which starts when onLongPress gets called. The timer stops when ´onLongPressEnd` gets called.
Try this:
import 'dart:async';
import 'package:flutter/material.dart';
void main() => runApp(const MyApp());
class MyApp extends StatefulWidget {
const MyApp({super.key});
#override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
String action = "START";
Timer? timer;
int number = 0;
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Material App',
home: Scaffold(
appBar: AppBar(
title: const Text('Material App Bar'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text(action),
SizedBox(height: 50),
Material(
borderRadius: BorderRadius.circular(20),
elevation: 20,
child: GestureDetector(
onTap: () => setState(() {
action = "Tap";
number++;
}),
onLongPress: () => setState(() {
timer = Timer.periodic(Duration(milliseconds: 50), (timer) {
setState(() {
action = "Longpress started";
number++;
});
});
}),
onLongPressEnd: (_) => setState(() {
action = "Longpress stopped";
timer?.cancel();
}),
child: Container(
alignment: Alignment.center,
decoration: BoxDecoration(
color: Colors.red[50],
borderRadius: BorderRadius.circular(20)
),
width: 100,
height: 100,
child: Text('Tap')
),
),
),
SizedBox(height: 50,),
Text(number.toString())
],
),
),
),
);
}
#override
void dispose() {
timer?.cancel();
super.dispose();
}
}
Proof:

Answer 2

Change your onlongpressStart.
do{
callback();
} while(btnPressed);
And on onlongpressEnd
setState(() => btnPressed = false);