Kotlin RecyclerView with LayoutInflater extension.

RecyclerAdapter.kt

class RecyclerAdapter(private val users: ArrayList<User>) : RecyclerView.Adapter<RecyclerAdapter.UserHolder>() {
    override fun getItemCount(): Int {
        return users.size
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerAdapter.UserHolder {
        // see Extensions.kt
        val inflatedView = parent.inflate(R.layout.list_row, false)
        return UserHolder(inflatedView)
    }

    fun insertUser(user: User) {
        users.add(user)
        notifyItemInserted(users.size - 1)
    }

    fun clear() {
        val size = users.size
        users.clear()
        notifyItemRangeRemoved(0, size)
    }

    override fun onBindViewHolder(holder: RecyclerAdapter.UserHolder, position: Int) {
        val user = users[position]
        val firstName = user.firstName + " #" + user.id

        holder.itemView.first_name.text = firstName
        holder.itemView.last_name.text = user.lastName
        holder.itemView.email.text = user.email

        holder.itemView.setOnClickListener({
            Log.d("RecyclerView", "CLICK ${user.firstName}!")

            val intent = Intent(holder.itemView.context, DetailActivity::class.java)
            intent.putExtra(DetailActivity.USER, user.id)
            holder.itemView.context.startActivity(intent)
        })
    }

    class UserHolder(v: View) : RecyclerView.ViewHolder(v)

}

RecyclerAdapterExtension.kt

fun ViewGroup.inflate(@LayoutRes layoutRes: Int, attachToRoot: Boolean = false): View {
    return LayoutInflater.from(context).inflate(layoutRes, this, attachToRoot)
}