A conversion of my MainActivity.java

MainActivity.kt

package com.cliftoncraig.apps.imagegallery

import android.app.ListActivity
import android.content.Context
import android.net.Uri
import android.os.Bundle
import android.util.Log
import android.view.KeyEvent
import android.view.Menu
import android.view.MenuItem
import android.view.inputmethod.InputMethodManager
import android.widget.EditText
import android.widget.TextView

import com.cliftoncraig.libs.parse.ResponseParse

import java.io.BufferedReader
import java.io.File
import java.io.IOException
import java.io.InputStream
import java.io.InputStreamReader
import java.net.MalformedURLException
import java.net.URL
import java.util.ArrayList
import java.util.HashMap


class MainActivity : ListActivity() {
    private var adapter: RowAdapter? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val searchField = findViewById(R.id.searchField) as EditText
        handleEnterKey(searchField, Runnable { doSearch(searchField.text.toString()) })
        adapter = RowAdapter(this)
        listAdapter = adapter
    }

    private fun createDataItems(): ArrayList<Map<String, String>> {
        val data = ArrayList<Map<String, String>>()
        data.add(makeItem(
                "image1", "https://tyrannyoftradition.files.wordpress.com/2012/05/cutest-kitten-hat-ever-13727-1238540322-17.jpg",
                "image2", "https://tyrannyoftradition.files.wordpress.com/2012/05/cutest-kitten-hat-ever-13727-1238540322-17.jpg",
                "image3", "https://tyrannyoftradition.files.wordpress.com/2012/05/cutest-kitten-hat-ever-13727-1238540322-17.jpg"))
        data.add(makeItem(
                "image1", "https://tyrannyoftradition.files.wordpress.com/2012/05/cutest-kitten-hat-ever-13727-1238540322-17.jpg",
                "image2", "https://tyrannyoftradition.files.wordpress.com/2012/05/cutest-kitten-hat-ever-13727-1238540322-17.jpg",
                "image3", "https://tyrannyoftradition.files.wordpress.com/2012/05/cutest-kitten-hat-ever-13727-1238540322-17.jpg"))
        data.add(makeItem(
                "image1", "https://tyrannyoftradition.files.wordpress.com/2012/05/cutest-kitten-hat-ever-13727-1238540322-17.jpg",
                "image2", "https://tyrannyoftradition.files.wordpress.com/2012/05/cutest-kitten-hat-ever-13727-1238540322-17.jpg",
                "image3", "https://tyrannyoftradition.files.wordpress.com/2012/05/cutest-kitten-hat-ever-13727-1238540322-17.jpg"))
        return data
    }

    private fun createDataItems(parsedURLs: List<URL>): List<Map<String, String>> {
        val data = ArrayList<Map<String, String>>()
        val numberOfRows = parsedURLs.size / 3
        val urls = parsedURLs.iterator()
        for (i in 0..numberOfRows - 1) {
            data.add(makeItem(
                    "image1", urls.next().toString(),
                    "image2", urls.next().toString(),
                    "image3", urls.next().toString()))
        }
        val extra = parsedURLs.size % 3
        if (extra > 0) {
            data.add(makeItem(
                    "image1", if (extra > 0) urls.next().toString() else "",
                    "image2", if (extra > 1) urls.next().toString() else "",
                    "image3", if (extra > 2) urls.next().toString() else ""))
        }
        return data
    }

    private fun handleEnterKey(searchField: EditText, onEnterAction: Runnable) {
        searchField.setOnEditorActionListener(TextView.OnEditorActionListener { v, actionId, event ->
            if (event != null && event.action == KeyEvent.ACTION_DOWN) {
                val inputMethod = getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
                inputMethod.hideSoftInputFromWindow(searchField.windowToken, InputMethodManager.HIDE_NOT_ALWAYS)
                Thread(onEnterAction).start()
                return@OnEditorActionListener true
            }
            false
        })
    }

    private fun doSearch(searchString: String) {
        //        URL[] imageUrls = getImages();
        val urlSpec = FLICKR_SEARCH_SPEC.format(searchString)
        val url: URL
        try {
            url = URL(urlSpec)
        } catch (e: MalformedURLException) {
            throw RuntimeException("Invalid search URL " + urlSpec, e)
        }

        val responseStream: InputStream
        try {
            responseStream = url.openStream()
        } catch (e: IOException) {
            throw RuntimeException("Could not load response for search URL " + urlSpec, e)
        }

        //        logServerResponse(urlSpec, responseStream);
        adapter!!.setData(createDataItems(ResponseParse().parse(responseStream)))
        runOnUiThread { adapter!!.notifyDataSetChanged() }
    }

    private fun logServerResponse(urlSpec: String, responseStream: InputStream) {
        val response = asString(responseStream)
        Log.i(javaClass.getName(), "***Server response***")
        Log.i(javaClass.getName(), urlSpec)
        Log.i(javaClass.getName(), response)
        Log.i(javaClass.getName(), "***Server response***")
    }

    private fun asString(inputStream: InputStream): String {
        val reader = BufferedReader(InputStreamReader(inputStream))
        val result = StringBuffer()
        try {
            var eachLine: String? = reader.readLine()
            while (eachLine != null) {
                result.append(eachLine)
                eachLine = reader.readLine()
            }
        } catch (e: IOException) {
            throw RuntimeException("Error readinf input stream.", e)
        }

        return result.toString()
    }

    private fun makeItem(key1: String, value1: String, key2: String, value2: String, key3: String, value3: String): HashMap<String, String> {
        val item = HashMap<String, String>()
        item.put(key1, value1)
        item.put(key2, value2)
        item.put(key3, value3)
        return item
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        // Inflate the menu; this adds items to the action bar if it is present.
        menuInflater.inflate(R.menu.menu_main, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        val id = item.itemId

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true
        }

        return super.onOptionsItemSelected(item)
    }

    companion object {

        val FLICKR_SEARCH_SPEC = "https://api.flickr.com/services/rest/?method=flickr.photos.search&api_key=af47a934f43272042601c3f903959027&format=json&nojsoncallback=1&text=%s"
    }

}