如何检查 LazyColumn 中的项目对于屏幕高度是否太少？

Question

Since there is no scrollbar for LazyColumn, I tried this solution.

Is there a way for me to check if items are too few for the list to scroll because the scrollbar is still visible and I want to hide it if possible?

Answer 1

In such cases you should use the lazy list state: it contains information about the visible elements, you need to check that all of them are fully visible.

When you need to read any state continuously and produce some value depending on this state, you should use derivedStateOf to prevent redundant recompositions.

val state = rememberLazyListState()
val canBeScrolled by remember {
    derivedStateOf {
        val layoutInfo = state.layoutInfo
        val visibleItemsInfo = layoutInfo.visibleItemsInfo
        if (layoutInfo.totalItemsCount == 0) {
            false
        } else {
            val firstVisibleItem = visibleItemsInfo.first()
            val lastVisibleItem = visibleItemsInfo.last()
            
            val viewportHeight = layoutInfo.viewportEndOffset + layoutInfo.viewportStartOffset)

            !(firstVisibleItem.index == 0 &&
                    firstVisibleItem.offset == 0 &&
                    lastVisibleItem.index + 1 == layoutInfo.totalItemsCount &&
                    lastVisibleItem.offset + lastVisibleItem.size <= viewportHeight)
        }
    }
}
LazyColumn(state = state) {
    // ...
}