Example imutable RecyclreView adapter made on Kotlin. Item click listener passed as parameter.

TestListAdapter.kt

package com.dementiev.realtest

import android.content.Context
import android.support.v7.widget.RecyclerView
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import android.util.TypedValue
import android.view.animation.AnimationUtils
import android.widget.LinearLayout
import android.widget.FrameLayout


/**
 * Example imutable adapter with animations
 */
class TestListAdapter(val context: Context, val items: List<Entity1>, val clickListener: (Entity1) -> Unit) : RecyclerView.Adapter<TestListAdapter.TestViewHolder1>() {
    /* // This is how our entity class looks
        data class Entity1(val _id: Int, val _text: String) {
            var id = _id
            var text = _text
        }
     */

    //optimization of resource usage
    private val DP16: Int = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 16f, context.resources.displayMetrics).toInt()

    // do not load the animation here, it wont be beauty, because it is instance of a tweener
    //private val animation: Animation = AnimationUtils.loadAnimation(context, android.R.anim.slide_in_left)


    override fun onBindViewHolder(holder: TestViewHolder1?, position: Int) {
        val item = getItem(position)
        holder?.label?.text = item.text
        holder?.container?.setOnClickListener { clickListener(item) }

        holder?.container?.let { animate(it) } // animate new view
    }

    private fun animate(root: View) {
        AnimationUtils
                .loadAnimation(context, android.R.anim.slide_in_left)
                .let(root::startAnimation)
    }

    override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): TestViewHolder1 {
        val layout = FrameLayout(parent?.context)
        val lp = LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT)
        layout.setPadding(0, DP16, 0, DP16)
        layout.layoutParams = lp

        val textView = TextView(parent?.context)
        val tlp = LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT)
        textView.layoutParams = tlp
        layout.addView(textView)

        return TestViewHolder1(layout, textView)
    }

    override fun getItemCount(): Int {
        return items.size
    }


    private fun getItem(position: Int): Entity1 {
        return items[position]
    }

    class TestViewHolder1(containerView: View?, textView: TextView?) : RecyclerView.ViewHolder(containerView) {
        var container: View? = containerView
        var label: TextView? = textView
    }
}