override fun doInBackground(vararg urls: URL): ArrayList<Valute> {

        val empList: ArrayList<Valute> = ArrayList()
        val url = URL("https://www.cbr-xml-daily.ru/daily.xml")

        val builderFactory = DocumentBuilderFactory.newInstance()
        val docBuilder = builderFactory.newDocumentBuilder()
        val doc = docBuilder.parse(url.openStream())

        val nList = doc.getElementsByTagName("Valute")
        for (i in 0 until nList.length) {

            val element = nList.item(i) as Element
            empList.add(
                Valute(
                    getNodeValue("NumCode", element),
                    getNodeValue("CharCode", element),
                    getNodeValue("Nominal", element),
                    getNodeValue("Name", element),
                    getNodeValue("Value", element)
                )
            )
        }

        return empList
    }

    fun getData(data: ArrayList<Valute>): ArrayList<Valute> {
        return data
    }

    override fun onProgressUpdate(vararg values: Int?) {
        super.onProgressUpdate(*values)
    }

    override fun onPostExecute(result: ArrayList<Valute>) {
        listener.onTaskCompleted(result)
    }

    fun getNodeValue(tag: String, element: Element): String{
        val nodeList = element.getElementsByTagName(tag)
        val node = nodeList.item(0)
        if(node != null){
            if(node.hasChildNodes()){
                val child = node.firstChild
                while(child!=null){
                    if(child.nodeType == Node.TEXT_NODE) return child.nodeValue
                }
            }
        }
        return ""
    }