ListAdapter(viewholder)1.kt

override fun getView(position: Int, view: View?, parent: ViewGroup?): View? {
    var convertView = view
    var viewHolder : ListViewHolder
    if (convertView == null) {
        convertView = LayoutInflater.from(context).inflate(layoutResId, parent, false)
        viewHolder = ListViewHolder()
        viewHolder.tvItem = convertView.tv_item
        convertView.tag = viewHolder
    }
    else {
        viewHolder = convertView.tag as ListViewHolder
    }

    viewHolder?.tvItem?.text = items[position]
    return convertView
 }

ListAdapter(viewholder)2.kt

class CustomViewHolder {
    var tvItem : TextView? = null
}