Using DiffUtil in Android RecyclerView

Extensions.kt

// See https://medium.com/@iammert/using-diffutil-in-android-recyclerview-bdca8e4fbb00

fun <T> RecyclerView.Adapter<*>.autoNotify(oldList: List<T>, newList: List<T>, compare: (T, T) -> Boolean) {
    val diff = DiffUtil.calculateDiff(object : DiffUtil.Callback() {

        override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
            return compare(oldList[oldItemPosition], newList[newItemPosition])
        }

        override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
            return oldList[oldItemPosition] == newList[newItemPosition]
        }

        override fun getOldListSize() = oldList.size

        override fun getNewListSize() = newList.size
    })

    diff.dispatchUpdatesTo(this)
}

ItemRecyclerAdapter.kt

class ItemRecyclerAdapter : RecyclerView.Adapter<ItemRecyclerAdapter.ItemHolder>() {

    var items: List<Item> by Delegates.observable(emptyList()) {
        _, old, new ->
        autoNotify(old, new) {
            o, n -> o.id == n.id
                && o.name == n.name
                && o.thumb == n.thumb
        }
    }

    override fun getItemCount(): Int {
        return items.size
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ItemHolder {
        // see Extensions.kt
        val inflatedView = parent.inflate(R.layout.card_row, false)
        return ItemHolder(inflatedView)
    }

    override fun onBindViewHolder(holder: ItemHolder?, position: Int) {
        val item = items[position]
        // ...
    }

    class ItemHolder(view: View) : RecyclerView.ViewHolder(view) {
        // ...
    }
}

MainActivity.kt

class MainActivity : DaggerAppCompatActivity() {
    // ...

    override fun onCreate(savedInstanceState: Bundle?) {
        // ..,.
        initAdapter()
        initViewModel()
        // ...
    }
	
	private fun initAdapter() {
        adapter = ItemRecyclerAdapter()
        linearLayoutManager = LinearLayoutManager(this)
        item_list.layoutManager = linearLayoutManager
        item_list.adapter = adapter
    }

    private fun initViewModel() {
        viewModel.getItems().observe(this, Observer {
            it?.let { data -> updateUI(data) }
        })
    }

    private fun updateUI(response: ItemsResponse) {
        var items = listOf(Item(name="Empty List"))

        when(response) {
            is ItemsResponse.Success -> {
                if (!response.items.isEmpty()) {
                    items = response.items
                }
            }
            is ItemsResponse.Error -> {
                Log.d(TAG, response.error)
                items = listOf(Item(name="Unknown Error"))
            }
        }

        adapter.items = items
    }
	
	// ...
}