Hi everyone, just wanted to ask if i have one Lazy...

# compose

[Sunil Kumar]

Hi everyone, just wanted to ask if i have one LazyColumn, and data list is dynamic, and for each item i need its global offset position. So im using remebered state variable for that and updating that using onGloballyPositioned modifier for each item. Is it fine to do that for each item inside items, or it can be bad practice and there can be a better alternative for this? Actually i need that global offset position during onLongPress on item. I know onLongPress also provides offset but that is relative to item composable but i need global position of each item while longPressing it.

[Natasha Jordanovska]

In Jetpack Compose, using onGloballyPositioned to get the global position of each item inside a LazyColumn is technically feasible, but it can lead to performance issues, especially with a dynamic and potentially large list. Each recomposition of an item in the list will trigger the onGloballyPositioned callback, which can be inefficient if the list updates frequently or contains many items.

[Sunil Kumar]

Yeah exactly, performance is my main concern. Thats why i asked this question. So then is there any other way out for getting that done?

[Natasha Jordanovska]

Instead of calculating the global position of each item upfront and storing it, consider capturing the global position when the long press event occurs. I think you can do this by using the Modifier.pointerInput in combination with detectTapGestures for handling long presses directly.

[Natasha Jordanovska]

Try something like this:

@Composable
fun MyList(items: List<String>) {
LazyColumn {
items(items) { item ->
ListItem(item = item, onLongPress = { globalOffset ->
println(“Global position: $globalOffset”)
})
}
}
}

@Composable
fun ListItem(item: String, onLongPress: (Offset) -> Unit) {
val view = LocalView.current
val density = LocalDensity.current

Box(
modifier = Modifier
.pointerInput(Unit) {
detectTapGestures(
onLongPress = { offset ->
val locationOnScreen = IntArray(2)
view.getLocationOnScreen(locationOnScreen)
val globalX = locationOnScreen[0] + with(density) { offset.x.toPx() }
val globalY = locationOnScreen[1] + with(density) { offset.y.toPx() }
onLongPress(Offset(globalX, globalY))
}
)
}
) {
// Your item’s UI goes here
}
}

[Sunil Kumar]

Wow, thats great. I was not even aware about this getLocationOnScreen method until now. Yes now it should work. Thanku so much. I will check it and update you. 🙏

[Sunil Kumar]

Hi @Natasha Jordanovska it not working. i guess getLocationOnScreen is returning the value almost similar to offset provided by onLongPress (tap position relative to current item composable) but not relative to device screen

[Natasha Jordanovska]

Try to capture the LocalView.current in the parent composable that contains your list and pass it to Each Child (ListItem)

[Sunil Kumar]

Still same location,I tried passing it from parent of list.