How to get LazyRow's visible items in viewmodel

Question

I have created a LazyRow in jetpack compose. At a certain point in the viewmodel, I want to get the list of currently visible items from that LazyRow. I know that I can get the list of visible items in the Composable function using the following code:

val listState = rememberLazyListState()
val visibleItemIds = remember {
    derivedStateOf { listState.layoutInfo.visibleItemsInfo.map { it.key.toString() } }
}

The problem is how can I pass this data to the viewmodel during a viewmodel event (not a button click etc)

Answer 1

You can add a side effect to know what are the visible items in any time.

LaunchedEffect(visibleItemIds){
   //update your viewModel
}

You can also have a List<T> instead of State<List<String>> as in your code with:

val state = rememberLazyListState()
val visibleItemIds: List<Int> by remember {
    derivedStateOf {
        val layoutInfo = state.layoutInfo
        val visibleItemsInfo = layoutInfo.visibleItemsInfo
        if (visibleItemsInfo.isEmpty()) {
            emptyList()
        } else {
            visibleItemsInfo.map { it.index }
        }
    }
}

Also note that visibleItemsInfo returns also the partially visible items.