DemoAdapterInterface.kt

//Sample adapter with click interface
class DemoAdapter(val adapterOnClick: AdapterOnClick) : RecyclerView.Adapter<DemoAdapter.DemoVH> {
  var itemList:MutableList<Any> = ArrayList()
  override fun onBindViewHolder(demoVH: DemoVH, i: Int) {
      demoVH.setItem(itemList.get(i))
  }
 
  /*
    implement other abstract method ..
  */
  
  inner class DemoVH : RecyclerView.ViewHolder {
    //button to be binded with our click callback
    var demoButton: Button
    constructor(itemView: View) : super(itemView){
        demoButton = itemView.findViewById(R.id.button)
    }
    //we set our button click listener here
    fun setItem(item: Any) {
        demoButton.setOnClickListener {adapterOnClick.onClick(item)}
    }
  }
}