DemoAdapter.kt

//Adapter having lambda function inside the constructor
class DemoAdapter(val adapterOnClick : (Any) -> Unit): RecyclerView.Adapter<DemoAdapter.DemoVH>(){
  var itemList:MutableList<Any> = ArrayList()
  override fun onBindViewHolder(demoVH: DemoVH, i: Int) {
        demoVH.setItem(itemList.get(i))
  }
  
  /*
    other abstract method implementation
  */
  
  inner class DemoVH : RecyclerView.ViewHolder {
    var demoButton: Button
    constructor(itemView: View) : super(itemView){
      demoButton = itemView.findViewById(R.id.button)
    }
    //set our click method here
    fun setItem(item: Any) {
      demoButton.setOnClickListener { adapterOnClick(item) }
    }
  }
}