Android Kotlin - Extract og tags from website using jsoup

JsoupOgTagParser.kt

class JsoupOgTagParser(var urlToParse: String) : AsyncTask<Void, Void, Void?>() {

	private var title: String? = null
	private var desc: String? = null
	private var image: String? = null
	private var url: String? = null
	private var listener: Listener? = null

	override fun doInBackground(vararg voids: Void): Void? {
		val con = Jsoup.connect(urlToParse)
		val doc = con.userAgent("Mozilla").get()

		val ogTags = doc.select("meta[property^=og:]")
		when {
			ogTags.size > 0 ->
			ogTags.forEachIndexed { index, element ->
				val tag = ogTags[index]
				val text = tag.attr("property")
				when (text) {
					"og:image" -> image = tag.attr("content")
					"og:description" -> desc = tag.attr("content")
					"og:url" -> url = tag.attr("content")
					"og:title" -> title = tag.attr("content")
				}
			}
		}
		return null
	}

	override fun onPostExecute(void: Void?) {
		super.onPostExecute(void)
		if (listener != null) {
			listener!!.onSuccess(title, url, desc, image)
		}
	}
	
	fun setListener(listener: Listener) {
		this.listener = listener
	}

	internal interface Listener {
		fun onSuccess(title: String?, url: String?, desc: String?, image: String?)
	}
}

JsoupOgTagParserInRx.kt

Flowable.fromCallable {
	val doc = Jsoup.connect(linkArray[0]).userAgent("Mozilla").get()
	val ogTags = doc.select("meta[property^=og:]")
	when {
		ogTags.size > 0 ->
			ogTags.forEachIndexed { index, element ->
				val tag = ogTags[index]
				val text = tag.attr("property")
				when (text) {
					"og:image" -> imagePreview = tag.attr("content")
					"og:description" -> descPreview = tag.attr("content")
					"og:url" -> urlPreview = tag.attr("content")
					"og:title" -> titlePreview = tag.attr("content")
				}
			}
	}
	}.subscribeOn(Schedulers.io())
		.observeOn(AndroidSchedulers.mainThread())
		.subscribe({
			setLinkPreviewOnScreen()
		})