Component-based adapter

Cmpnt.kt

class CmpntViewHolder<T>(val cmpnt: Cmpnt<T>, view: View) : RecyclerView.ViewHolder(view)

abstract class Cmpnt<T>(@field:LayoutRes private val cmpntLayoutId: Int) {

    open fun setData(data: T) {}

    protected open fun onViewCreated(view: View) {}

    fun createView(inflater: LayoutInflater, parent: ViewGroup?): View {
        val view = inflater.inflate(cmpntLayoutId, parent, false)
        onViewCreated(view)
        return view
    }

    fun onVisible() {}

    fun onHidden() {}
}

CmpntrRecyclerAdapter.kt

class CmpntrRecyclerAdapter(private val layoutInflater: LayoutInflater) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

    private var items: List<Any> = listOf()
    fun setItems(newItems: List<Any>): Boolean {
        val oldItems = items
        items = newItems as MutableList<Any>

        DiffUtil.calculateDiff(SimpleDiffUtilCallback(newItems, oldItems)).dispatchUpdatesTo(this)

        return oldItems != newItems
    }

    //public to be accessible by `register` inline function
    var cmpntProviders = LinkedHashMap<Class<out Any>, () -> Cmpnt<*>>()

    inline fun <reified T : Any> register(noinline cmpntProvider: () -> Cmpnt<T>) {
        cmpntProviders[T::class.java] = cmpntProvider
    }

    override fun getItemViewType(position: Int) = cmpntProviders.keys.indexOf(items[position].javaClass)
    override fun getItemId(position: Int): Long = position.toLong()
    override fun getItemCount() = items.size

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
        val cmpnt = cmpntProviders.values.elementAt(viewType)()
        return CmpntViewHolder(cmpnt, cmpnt.createView(layoutInflater, parent))
    }

    @Suppress("UNCHECKED_CAST")
    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        (holder as CmpntViewHolder<Any>).cmpnt.setData(items[position])
    }

    @Suppress("UNCHECKED_CAST")
    override fun onViewAttachedToWindow(holder: RecyclerView.ViewHolder) {
        super.onViewAttachedToWindow(holder)
        (holder as CmpntViewHolder<Any>).cmpnt.onVisible()
    }

    @Suppress("UNCHECKED_CAST")
    override fun onViewDetachedFromWindow(holder: RecyclerView.ViewHolder) {
        super.onViewDetachedFromWindow(holder)
        (holder as CmpntViewHolder<Any>).cmpnt.onHidden()
    }
}

GleamComponent.kt

//as an example how to use Cmpnt
//first setup an adapter somewhere and register components on it
class CmpntrLib @Inject constructor(
        private val gleamCmpntProvider: Provider<GleamCmpnt>,
) {
    fun setup(recycler: RecyclerView, adapter: CmpntrRecyclerAdapter) {
        recycler.adapter = adapter

        adapter.apply {
            register { gleamCmpntProvider.get() }
        }
    }
}

class GleamCmpnt @Inject constructor(
        private val timeHelper: TimeHelper,
        private val analytics: FirebaseAnalytics
) : Cmpnt<GleamEntry>(R.layout.cmpnt_gleam_long) {

    lateinit var binding: CmpntGleamLongBinding

    override fun setData(data: GleamEntry) {
        super.setData(data)
        binding.data = data
        binding.executePendingBindings()
    }

    override fun onViewCreated(view: View) {
        super.onViewCreated(view)
        binding = DataBindingUtil.bind(view)!!
        binding.cmpnt = this
        binding.timeHelper = timeHelper
    }

    fun click(view: View) {
//...
    }

    fun clickSource(view: View) {
//    ...
    }
}

SimpleDiffUtilCallback.kt

class SimpleDiffUtilCallback<T>(
        protected val newItems: List<T>,
        protected val oldItems: List<T>
) : DiffUtil.Callback() {

    override fun getOldListSize() = oldItems.size
    override fun getNewListSize() = newItems.size

    override fun areItemsTheSame(oldPosition: Int, newPosition: Int) = newItems[newPosition] == oldItems[oldPosition]
    override fun areContentsTheSame(oldPosition: Int, newPosition: Int) = newItems[newPosition] == oldItems[oldPosition]
}