Generic RecyclerAdapter implementtion using DiffUtils

DiffUtilsActivity.kt

private lateinit var adapter: GenericListAdapter<ImagesInfo>

adapter = GenericListAdapter(R.layout.product_view) { item, position ->
            viewModel.setSelectedProduct(item)
            findNavController().navigate(ImageListFragmentDirections.actionImageListFragmentToImageDetailFragment())
        }

GenericListAdapter.kt

// Adapter
class GenericListAdapter<T> internal constructor(
    @IdRes private val layout: Int,
    private val clickListener: (item: T, position: Int) -> Unit
) : RecyclerView.Adapter<GenericViewHolder<T>>() {

    var productItems: ArrayList<T> = ArrayList()
        set(value) {
            field = value
            val diffCallback =
                GenericViewHolder.ChildViewDiffUtils(filteredProductItems, productItems)
            val diffResult = DiffUtil.calculateDiff(diffCallback)
            if (filteredProductItems.size > 0)
                filteredProductItems.clear()
            filteredProductItems.addAll(value)
            diffResult.dispatchUpdatesTo(this)
        }

    private var filteredProductItems: ArrayList<T> = ArrayList()
        set(value) {
            field = value
            val diffCallback =
                GenericViewHolder.ChildViewDiffUtils(filteredProductItems, productItems)
            val diffResult = DiffUtil.calculateDiff(diffCallback)
            diffResult.dispatchUpdatesTo(this)
        }

    fun clearProductItem() {
        filteredProductItems.clear()
    }

    override fun onCreateViewHolder(viewGroup: ViewGroup, i: Int): GenericViewHolder<T> {
        val layoutInflater = LayoutInflater.from(viewGroup.context)
        val binding = DataBindingUtil.inflate<ViewDataBinding>(layoutInflater, i, viewGroup, false)
        return GenericViewHolder(binding)
    }

    override fun onBindViewHolder(holder: GenericViewHolder<T>, i: Int) {
        val item = filteredProductItems[i]
        holder.bind(item)
        holder.itemView.parentLayout.setOnClickListener {
            clickListener(item, i)
        }
    }

    override fun getItemCount(): Int = filteredProductItems.size

    override fun getItemViewType(position: Int) = layout

}

GenericViewHolder.kt

// ViewHolder
class GenericViewHolder<T>(private val bi: ViewDataBinding) :
    RecyclerView.ViewHolder(bi.root) {

    fun bind(item: T) {
        bi.apply {
            bi.setVariable(BR.item, item)
            bi.executePendingBindings()
        }
    }

    class ChildViewDiffUtils<T>(
        private val oldList: ArrayList<T>,
        private val newList: ArrayList<T>
    ) :
        DiffUtil.Callback() {
        override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
            return oldList[oldItemPosition].toString() == newList[newItemPosition].toString()
        }

        override fun getOldListSize(): Int {
            return oldList.size
        }

        override fun getNewListSize(): Int {
            return newList.size
        }

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

Hi @AliAzaz is the code right? In the overridden method areItemsTheSame you are using .toString which will fail for example for a

data class Car(val registrationId: Long, val currentColor: String)

for the same registered car Car(registrationId = "abc", currentColor = "red") and Car(registrationId = "abc", currentColor = "yellow") your code will treat these as different item while only areContentsTheSame should return false as these two elements have different data. But you code will WRONGLY return the areItemsTheSame as false as well.

Or is this code specific to your use case only? In that case it should not be present inside GenericViewHolder.kt