additional_functions.kt

class PageAdapter(private val items: List<Item>) : RecyclerView.Adapter<PageAdapter.ViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.item, parent, false))
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.item.setBackgroundColor(items[getRealPosition(position)].color)
    }

    override fun getItemCount(): Int {
        if (items.size <= 1) {
            return items.size
        }
        val period = Int.MAX_VALUE / 2 / items.size
        return period * items.size * 2
    }

    fun getMiddlePosition() = itemCount / 2

    fun getListSize() = items.size

    private fun getRealPosition(position: Int) = position % getListSize()

    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        val item: ImageView = view.findViewById(R.id.item)
    }
}