Android RecyclerView Example with Retrofit library using Kotlin.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.suresh.myapplication.MainActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerview_demo"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</android.support.constraint.ConstraintLayout>

ApiClient.kt

package com.suresh.retrofitdemo

import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory

/**
 * Created by Dumadu on 26-Oct-17.
 */
public class ApiClient {
    public var BASE_URL: String = "https://next.json-generator.com/api/json/get/"
    public var retrofit: Retrofit? = null

    public fun getApiClient(): Retrofit? {
        if (retrofit == null) {
            retrofit = Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create()).build()
        }
        return retrofit
    }
}

ApiInterface.kt

package com.suresh.retrofitdemo

import retrofit2.Call
import retrofit2.http.POST

/**
 * Created by Dumadu on 26-Oct-17.
 */
public interface ApiInterface {

    @POST("E1Pn7khWG")
    fun getHospitalsList(): Call<ArrayList<Hospitals>>
}

Hospitals.kt

package com.suresh.retrofitdemo

import com.google.gson.annotations.SerializedName

/**
 * Created by Dumadu on 26-Oct-17.
 */
public class Hospitals {
    public var id: String? = null
    @SerializedName("hospital_name")
    public var hospitalName: String? = null
    public var address: String? = null
}

item_list.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/image_picture"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:padding="5dp"
        android:src="@mipmap/ic_launcher_round" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="5dp">

        <TextView
            android:id="@+id/text_name"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Name"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/text_address"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Message" />
    </LinearLayout>

</LinearLayout>

MainActivity.kt

package com.suresh.retrofitdemo

import android.os.Bundle
import android.support.v7.app.AlertDialog
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.DividerItemDecoration
import android.support.v7.widget.LinearLayoutManager
import android.support.v7.widget.RecyclerView
import android.widget.Toast
import com.example.suresh.myapplication.R
import retrofit2.Call
import retrofit2.Callback
import retrofit2.Response

/**
 * Created by Dumadu on 26-Oct-17.
 */
class MainActivity : AppCompatActivity(), RecyclerViewAdapter.hospitalClickListener {
    var hospitalsData: ArrayList<Hospitals> = ArrayList()
    override fun getItem(position: Int) {
        val alertDialog = AlertDialog.Builder(this@MainActivity)
        alertDialog.setTitle(hospitalsData.get(position).hospitalName)
        alertDialog.setMessage(hospitalsData.get(position).address)
        alertDialog.setPositiveButton("OK") { dialog, which ->
            Toast.makeText(this@MainActivity, "OK", Toast.LENGTH_SHORT).show()
        }
//        alertDialog.setNegativeButton("No") { dialog, which ->
//            Toast.makeText(this@MainActivity, "No", Toast.LENGTH_SHORT).show()
//        }
        alertDialog.show()
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        var recyclerView: RecyclerView = findViewById(R.id.recyclerview_demo)
        recyclerView.layoutManager = LinearLayoutManager(this)
        recyclerView.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))
        var apiInterface: ApiInterface = ApiClient().getApiClient()!!.create(ApiInterface::class.java)
        apiInterface.getHospitalsList().enqueue(object : Callback<ArrayList<Hospitals>> {
            override fun onResponse(call: Call<ArrayList<Hospitals>>?, response: Response<ArrayList<Hospitals>>?) {
                hospitalsData = response?.body()!!
                recyclerView.adapter = RecyclerViewAdapter(response?.body()!!, this@MainActivity)
            }

            override fun onFailure(call: Call<ArrayList<Hospitals>>?, t: Throwable?) {
            }
        })


    }
}

RecyclerViewAdapter.kt

package com.suresh.retrofitdemo

import android.support.v7.widget.RecyclerView
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import com.example.suresh.myapplication.R

/**
 * Created by Dumadu on 26-Oct-17.
 */
class RecyclerViewAdapter(var hospitalsList: ArrayList<Hospitals>?, var itemClick: hospitalClickListener) : RecyclerView.Adapter<RecyclerViewAdapter.RecyclerViewHolder>() {
    override fun getItemCount(): Int {
        return hospitalsList!!.size
    }

    interface hospitalClickListener {
        fun getItem(position: Int)
    }

    override fun onBindViewHolder(holder: RecyclerViewHolder, position: Int) {
        holder.bindData(hospitalsList, position)
    }

    override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): RecyclerViewHolder {
        var view: View = LayoutInflater.from(parent!!.context).inflate(R.layout.item_list, parent, false)
        return RecyclerViewHolder(view, itemClick)
    }

        class RecyclerViewHolder(itemView: View, var itemClick: hospitalClickListener) : RecyclerView.ViewHolder(itemView) {
//    class RecyclerViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        var textName: TextView = itemView.findViewById(R.id.text_name)
        var textAddress: TextView = itemView.findViewById(R.id.text_address)
        fun bindData(hospitalsList: ArrayList<Hospitals>?, position: Int) {
            textName.text = hospitalsList!!.get(position).hospitalName
            textAddress.text = hospitalsList!!.get(position).address
            itemView.setOnClickListener(View.OnClickListener {
                itemClick.getItem(adapterPosition)
            })
        }
    }
}

thank you very much