https://ferrand-d.medium.com/paging-image-gallery-with-recyclerview-f059d035b7e7

PagingImageGallery_initialPosition.kt

private fun initRecyclerViewPosition(position: Int) {
    // This initial scroll will be slightly off because it doesn't
    // respect the SnapHelper. Do it anyway so that the target view
    // is laid out, then adjust onPreDraw.

    layoutManager.scrollToPosition(position)

    recyclerView.doOnPreDraw {
        val targetView = layoutManager.findViewByPosition(position)
                ?: return@doOnPreDraw

        val distanceToFinalSnap = snapHelper.calculateDistanceToFinalSnap(layoutManager, targetView)
                ?: return@doOnPreDraw

        layoutManager.scrollToPositionWithOffset(position, -distanceToFinalSnap[0])
    }
}