dk_mvp_6.kt

override fun onUpdatedItem(oldItem: Item, newItem: Item) {
    tv_item.text = "${getItemStr(oldItem)} -> ${getItemStr(newItem)}"
    iv_item.setBackgroundColor(ContextCompat.getColor(this, when (newItem) {
        ITEM_A -> R.color.red
        ITEM_B -> R.color.green
        ITEM_C -> R.color.blue
    }))
}

private fun getItemStr(item: Item): String = getString(when (item) {
    ITEM_A -> R.string.a
    ITEM_B -> R.string.b
    ITEM_C -> R.string.c
})