BaseDiffCallback.kt

open class BaseDiffCallback<T>(
        var itemsOld: List<T> = listOf(),
        var itemsNew: List<T> = listOf()
) : DiffUtil.Callback() {

    lateinit var areItemsTheSame: ((oldItemPosition: Int, newItemPosition: Int) -> Boolean)

    lateinit var areContentTheSame: ((oldItemPosition: Int, newItemPosition: Int) -> Boolean)

    override fun getOldListSize(): Int = itemsOld.size

    override fun getNewListSize(): Int = itemsNew.size

    override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
        return areItemsTheSame.invoke(oldItemPosition, newItemPosition)
    }

    override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
        return areContentTheSame.invoke(oldItemPosition, newItemPosition)
    }
}

usage.kt

private val diffCallback = BaseDiffCallback<User>().apply {
    areItemsTheSame = { oldItemPosition, newItemPosition ->
        itemsOld[oldItemPosition].id == itemsNew[newItemPosition].id
    }
    areContentTheSame = { oldItemPosition, newItemPosition -> true }
}