Adds start/end padding to first/last item of a horizontal RecyclerView (like Play Store app)

HorizontalPaddingItemDecoration.kt

class HorizontalPaddingItemDecoration(
        private val paddingStart: Int = 0,
        private val paddingEnd: Int = 0
) : RecyclerView.ItemDecoration() {

    private var isRtl: Boolean? = null
    
    fun isRTL(ctx: Context): Boolean {
        val config = ctx.resources.configuration
        return config.layoutDirection == View.LAYOUT_DIRECTION_RTL
    }

    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State?) {
        super.getItemOffsets(outRect, view, parent, state)

        if (isRtl == null) {
            isRtl = isRTL(view.context)
        }

        val position = parent.getChildAdapterPosition(view)

        if (position == 0) {
            if (!isRtl!!) {
                outRect.left += paddingStart
            } else {
                outRect.right += paddingStart
            }
        } 
        if (position == parent.adapter.itemCount - 1) {
            if (!isRtl!!) {
                outRect.right += paddingEnd
            } else {
                outRect.left += paddingEnd
            }
        }
    }
}

RecyclerView's adapter can be null. Just suggesting

parent.adapter?.let {
            if (position == it.itemCount - 1) {
                if (!isRtl!!) {
                    outRect.right += paddingEnd
                } else {
                    outRect.left += paddingEnd
                }
            }
        }