How to notice when user released his/her finger from scrolling - flutter

Question

I have a listView.Builder and want to do certain calculation based on position of scrollController when user released his/her finger on the screen?
the calculation part is easy in flutter but How can I notice when user released his finger from scrolling to do some action ?

Answer 1

This worked for me:
class _YourScreenState extends State<YourScreen> {
bool _isDragging = false;
ScrollUpdateNotification _notification;
#override
Widget build(BuildContext context) {
return NotificationListener<ScrollUpdateNotification>(
onNotification: (notification) {
_notification = notification;
if (_hasLiftedFinger) {
// do your thing
}
_setDraggingState();
// confidently use _isDragging here
return false;
},
child: YourListView(),
);
}
void _setDraggingState() {
if (_hasLoweredFinger) {
_isDragging = true;
return;
}
if (_hasLiftedFinger) {
_isDragging = false;
}
}
bool get _hasLoweredFinger => (!_isDragging && _notification.dragDetails != null);
bool get _hasLiftedFinger => (_isDragging && _notification.dragDetails == null);
}

Answer 2

Use NotificationListener Widget. Here is a short clip about it.
The code you may want would look like this:
#override
Widget build(BuildContext context) {
return NotificationListener<ScrollNotification>(
onNotification: (notification) {
if (notification is ScrollStartNotification) {
debugPrint('Started');
}
if (notification is ScrollUpdateNotification) {
debugPrint('Updated');
}
if (notification is ScrollEndNotification) {
debugPrint('Ended');
}
return false;
},
child: YourListView(),
);
}