Kotlin abstract class with generic param and methods which use type param

Question

I\'m trying to create an abstract class with generic parameter which will have subclasses which should call methods without having to specify type parameters

Answer 1

Thanks to Fabian Zeindly I wrote a variant for several extended classes. In this case all of them should be declared in a title of an abstract class.

abstract class AbstractAdapter : RecyclerView.Adapter() {

    var list: List = emptyList()

    override fun getItemCount(): Int = list.size

    open fun setItems(list: List) {
        this.list = list.toMutableList()
    }

    open class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)

    open class Item
}

Then extend the class with new inner classes (ViewHolder, Item).

class NewAdapter(private var listener: View.OnClickListener?) : AbstractAdapter() {

    private var originalItems: List = emptyList()

    override fun setItems(list: List) {
        super.setItems(list)
        this.originalItems = list.toMutableList()
        this.list = list.toMutableList()
    }

    override fun onCreateViewHolder(viewGroup: ViewGroup, i: Int): ViewHolder {
        val view = LayoutInflater.from(viewGroup.context)
            .inflate(R.layout.layout, viewGroup, false)

        return ViewHolder(view)
    }

    override fun onBindViewHolder(viewHolder: ViewHolder, i: Int) {
        val item = list[i]
        viewHolder.textView.text = item.text
        viewHolder.textView.tag = item.id
    }

    class ViewHolder(itemView: View) : AbstractAdapter.ViewHolder(itemView) {
        val textView: TextView = itemView.name
    }

    class Item(val id: Int, val text: String) : AbstractAdapter.Item()
}