DataBindingAdapter for RecyclerView (MVVM)

DataBindingAdapter.kt

abstract class DataBindingAdapter<T>(
    private val variableId: Int,
    diffCallback: DiffUtil.ItemCallback<T>
) : ListAdapter<T, DataBindingAdapter.DataBindingViewHolder<T>>(diffCallback) {

    private var list: List<T>? = emptyList()

    private lateinit var onItemViewClick: ((View, T, Int) -> Unit?)
    private lateinit var clickableIds: IntArray

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DataBindingViewHolder<T> {
        val layoutInflater = LayoutInflater.from(parent.context)
        val binding = DataBindingUtil.inflate<ViewDataBinding>(layoutInflater, viewType, parent, false)

        return DataBindingViewHolder(binding, variableId)
    }

    override fun onBindViewHolder(holder: DataBindingViewHolder<T>, position: Int) {
        holder.apply {
            bind(getItem(position))

            if (::onItemViewClick.isInitialized && ::clickableIds.isInitialized) {
                val clickListener = View.OnClickListener { view ->
                    list?.get(holder.adapterPosition)?.let {
                        onItemViewClick.invoke(view, it, holder.adapterPosition)
                    }
                }
                for (clickableId in clickableIds) {
                    holder.itemView.findViewById<View>(clickableId)?.setOnClickListener(clickListener)
                }
            }
        }
    }

    override fun submitList(list: List<T>?) {
        super.submitList(list)
        this.list = list
    }

   fun setOnItemViewClickListener(
        onItemViewClick: (view: View, model: T, position: Int) -> Unit,
        vararg ids: Int
    ) {
        this.onItemViewClick = onItemViewClick
        this.clickableIds = ids
    }

    class DataBindingViewHolder<T>(
        private val binding: ViewDataBinding,
        private val variableId: Int
    ) : RecyclerView.ViewHolder(binding.root) {

        fun bind(item: T) {
            binding.setVariable(variableId, item)
            binding.executePendingBindings()
        }
    }

}

item_postponed.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>
        <variable
                name="postponedListModel"
                type="ru.holofox.anicoubs.data.db.unitlocalized.vk.UnitSpecificVKWallMinimalEntry" />
    </data>

    <com.google.android.material.card.MaterialCardView
            android:id="@+id/cardView_postponed"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:minHeight="?listPreferredItemHeightLarge"
            android:layout_margin="4dp"
            app:cardCornerRadius="4dp">

        <androidx.constraintlayout.widget.ConstraintLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:minHeight="?listPreferredItemHeightLarge">
          
          <!-- ... -->
          
        </androidx.constraintlayout.widget.ConstraintLayout>

    </com.google.android.material.card.MaterialCardView>
</layout>

PostponedAdapter.kt

class PostponedAdapter :
    DataBindingAdapter<UnitSpecificVKWallMinimalEntry>(BR.postponedListModel, DiffCallback()) {

    class DiffCallback : DiffUtil.ItemCallback<UnitSpecificVKWallMinimalEntry>() {
        override fun areItemsTheSame(
            oldItem: UnitSpecificVKWallMinimalEntry,
            newItem: UnitSpecificVKWallMinimalEntry
        ): Boolean = oldItem.id == newItem.id

        override fun areContentsTheSame(
            oldItem: UnitSpecificVKWallMinimalEntry,
            newItem: UnitSpecificVKWallMinimalEntry
        ): Boolean = oldItem == newItem
    }

    override fun getItemViewType(position: Int) = R.layout.item_postponed
}

PostponedListFragment.kt

class PostponedListFragment : Fragment() {

    ...

    private var viewModelAdapter: PostponedAdapter? = null
    private val onItemMore: (View) -> Unit = { }
    
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?): View? {

        binding = DataBindingUtil.inflate(
            inflater,
            R.layout.postponed_list_fragment,
            container,
            false
        )

        viewModelAdapter = PostponedListAdapter().apply {
            setOnItemViewClickListener({view, model, position ->
                when (view.id) {
                    R.id.cardView_postponed -> showPostponedDetail(view)
                    R.id.imageView_more -> onItemMore(view)
                }
            }, R.id.imageView_more, R.id.cardView_postponed)
        }

        binding.apply {
            lifecycleOwner = viewLifecycleOwner
            postponedViewModel = viewModel
            recyclerView.adapter = viewModelAdapter
        }

        return binding.root
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)

        viewModel.wall.observe(viewLifecycleOwner, Observer { entries ->
            entries?.let {
                viewModelAdapter?.submitList(entries)
            }
        })
    }
    
    private fun showPostponedDetail(view: View) { }
    
    ...
    
}