How to find percentage of each visible item in recycleview

Question

int findFirstVisibleItemPosition();
int findFirstCompletelyVisibleItemPosition();
int findLastVisibleItemPosition();
int findLastCompletelyVisibleItemPosition();
         


        

Answer 1

Here is an improved (more effective, less memory usage, less code, updates ViewHolder with the current extent of its visibility) Kotlin version of Vishal Sanghani's answer:

recycler.addOnScrollListener(object : RecyclerView.OnScrollListener() {
    override fun onScrolled(recyclerView: RecyclerView?, dx: Int, dy: Int) {
        val layoutManager = recycler.layoutManager as LinearLayoutManager
        val firstPosition = layoutManager.findFirstVisibleItemPosition()
        val lastPosition = layoutManager.findLastVisibleItemPosition()

        val globalVisibleRect = Rect()
        val itemVisibleRect = Rect()

        recycler.getGlobalVisibleRect(globalVisibleRect)

        for (pos in firstPosition..lastPosition) {
            val view = layoutManager.findViewByPosition(pos)
            if (view != null && view.height > 0 && view.getGlobalVisibleRect(itemVisibleRect)) {
                val visibilityExtent = if (itemVisibleRect.bottom >= globalVisibleRect.bottom) {
                    val visibleHeight = globalVisibleRect.bottom - itemVisibleRect.top
                    Math.min(visibleHeight.toFloat() / view.height, 1f)
                } else {
                    val visibleHeight = itemVisibleRect.bottom - globalVisibleRect.top
                    Math.min(visibleHeight.toFloat() / view.height, 1f)
                }

                val viewHolder = recycler.findViewHolderForAdapterPosition(pos) as ViewHolder
                viewHolder.setVisibilityExtent(visibilityExtent)

                // if percentage is needed...
                val percentage = visibilityExtent * 100

            }
        }
    }
})