Adapter realization based on RecyclerView.Adapter using DiffUtil callback

ITestBaseAdapter

interface ITestBaseAdapter<T : Any> {
    fun add(item: T)
    fun addAll(items: List<T>)
    fun addTo(position: Int = 0, item: T)
    fun remove(position: Int)
    fun getList(): List<T>
    fun update(newList: List<T>, callback: ApolloBaseDiffUtilCallback<T>)
    fun clear()
}

TestBaseAdapter

abstract class TestBaseAdapter<VH : TestBaseViewHolder> : RecyclerView.Adapter<VH>(), ITestBaseAdapter<Any> {

    private val items: MutableList<Any> = mutableListOf()

    override fun add(item: Any) {
        items += item
        notifyItemInserted(items.lastIndex)
    }

    override fun addAll(items: List<Any>) {
        if (items.isEmpty()) return

        val startPosition = this.items.lastIndex + 1
        for (item in items) {
            this.items += item
        }
        notifyItemRangeInserted(startPosition, items.size)
    }

    override fun addTo(position: Int, item: Any) {
        items.add(position, item)
        notifyItemChanged(position)
    }

    override fun remove(position: Int) {
        items.removeAt(position)
        notifyItemRemoved(position)
    }

    override fun clear() {
        val removedSize = items.size
        items.clear()
        notifyItemRangeRemoved(0, removedSize)
    }

    override fun update(newList: List<Any>, callback: ApolloBaseDiffUtilCallback<Any>) {
        callback.setLists(items, newList)
        val diffResult = DiffUtil.calculateDiff(callback)
        clear()
        addAll(newList)
        diffResult.dispatchUpdatesTo(this)
    }
    
    override fun getList(): List<Any> = items

    override fun getItemCount(): Int = items.size

    protected fun inflate(parent: ViewGroup, @LayoutRes viewType: Int): View =
        LayoutInflater.from(parent.context).inflate(viewType, parent, false)

    override fun onBindViewHolder(holder: VH, position: Int) {
        holder.bind(items[position], position)
    }

}

TestBaseViewHolder

abstract class TestBaseViewHolder(view: View) : RecyclerView.ViewHolder(view) {
    abstract fun bind(T: Any, position: Int)
}

TestCallback

abstract class ApolloBaseDiffUtilCallback<T : Any> : DiffUtil.Callback() {
    var oldList: List<T> = listOf()
    var newList: List<T> = listOf()

    fun setLists(oldList: List<T>, newList: List<T>) {
        this.oldList = oldList
        this.newList = newList
    }

    override fun getNewListSize(): Int = this.newList.size

    override fun getOldListSize(): Int = this.oldList.size
}