“Multiples veces se presenta un elemento de lista repetido en un recycler-view al usar Paging v3.”

He implementado android-paging v3 siguiendo https://proandroiddev.com/paging-3-easier-way-to-pagination-part-1-584cad1f4f61 & https://proandroiddev.com/how-to-use-the-paging-3-library-in-android-part-2-e2011070a37d. Pero veo que los datos se están poblado varias veces incluso cuando solo hay 3 registros en la base de datos local.

Pantalla de lista de notificaciones

¿Alguien puede sugerir qué estoy haciendo mal? Gracias de antemano.

Mi código es el siguiente:

NotificationsFragment

class NotificationsFragment : Fragment() {

    private lateinit var binding: FragmentNotificationsBinding
    private val alertViewModel: NotificationsViewModel by viewModel()

    private val pagingAdapter by lazy { AlertsPagingAdapter() }

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        binding = FragmentNotificationsBinding.inflate(inflater, container, false)
        return binding.root
    }

    override fun onResume() {
        super.onResume()
        (activity as MainActivity).setUpCustomToolbar(
            getString(R.string.alerts),
            ""
        )
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        binding.lifecycleOwner = viewLifecycleOwner
        initRecyclerView()
    }

    private fun initRecyclerView() {
        binding.rvAlerts.apply {
            adapter = pagingAdapter.withLoadStateFooter(AlertLoadStateAdapter {})
            layoutManager = LinearLayoutManager(requireContext())
        }

        lifecycleScope.launch {
            alertViewModel.alertListFlow.collectLatest { pagingData ->
                pagingAdapter.submitData(
                    pagingData
                )
            }
        }
    }

}

NotificationsViewModel

class NotificationsViewModel(private val useCase: NotificationsUseCase) : BaseViewModel() {

    val alertListFlow = Pager(PagingConfig(1)) { NotificationsPagingSource(useCase) }
        .flow
        .cachedIn(viewModelScope)
}

NotificationsPagingSource

import androidx.paging.PagingSource
import androidx.paging.PagingState
import com.example.demo.model.entity.Notifications
import com.example.demo.NotificationsUseCase

class NotificationsPagingSource(private val useCase: NotificationsUseCase) : PagingSource() {

    private companion object {
        const val INITIAL_PAGE_INDEX = 0
    }

    override suspend fun load(params: LoadParams): LoadResult {
        val position = params.key ?: INITIAL_PAGE_INDEX
        val randomNotifications: List = useCase.fetchNotifications(params.loadSize)
        return LoadResult.Page(
            data = randomNotifications,
            prevKey = if (position == INITIAL_PAGE_INDEX) null else position - 1,
            nextKey = if (randomAlerts.isNullOrEmpty()) null else position + 1
        )
    }

    override fun getRefreshKey(state: PagingState): Int? {

        // Necesitamos obtener la clave anterior (o la siguiente si la anterior es nula) de la página
        // que estuvo más cerca del índice más recientemente accedido.
        // La posición de anclaje es el índice más recientemente accedido
        return state.anchorPosition?.let { anchorPosition ->
            state.closestPageToPosition(anchorPosition)?.prevKey?.plus(1)
                ?: state.closestPageToPosition(anchorPosition)?.nextKey?.minus(1)
        }
    }
}

PagingAdapter

import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.paging.PagingDataAdapter
import androidx.recyclerview.widget.DiffUtil
import androidx.recyclerview.widget.RecyclerView


class NotificationsPagingAdapter :
    PagingDataAdapter(NotificationsEntityDiff()) {

    override fun onBindViewHolder(holder: ItemNotificationsViewHolder, position: Int) {
        getItem(position)?.let { userPostEntity -> holder.bind(userPostEntity) }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ItemNotificationsViewHolder {
        return ItemNotificationsViewHolder(
            ItemLayoutNotificationsBinding.inflate(
                LayoutInflater.from(parent.context),
                parent,
                false
            )
        )
    }

    /**
     * Viewholder for each Notifications layout item
     */
    inner class ItemNotificationsViewHolder(private val binding: ItemLayoutNotificationsBinding) :
        RecyclerView.ViewHolder(binding.root) {
        fun bind(alert: Notifications) {
            binding.tvMessage.text = alert.title
        }
    }

    class NotificationsEntityDiff : DiffUtil.ItemCallback() {
        override fun areItemsTheSame(oldItem: Notifications, newItem: Notifications): Boolean =
            oldItem.id == newItem.id

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

NotificationsLoadStateAdapter

class NotificationsLoadStateAdapter(
    private val retry: () -> Unit
) : LoadStateAdapter() {

    override fun onBindViewHolder(holder: LoadStateViewHolder, loadState: LoadState) {

        val progress = holder.itemView.load_state_progress
        val btnRetry = holder.itemView.load_state_retry
        val txtErrorMessage = holder.itemView.load_state_errorMessage

        btnRetry.isVisible = loadState !is LoadState.Loading
        // txtErrorMessage.isVisible = loadState !is LoadState.Loading
        progress.isVisible = loadState is LoadState.Loading

        if (loadState is LoadState.Error) {
           // txtErrorMessage.text = loadState.error.localizedMessage
        }

        btnRetry.setOnClickListener {
            retry.invoke()
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, loadState: LoadState): LoadStateViewHolder {
        return LoadStateViewHolder(
            LayoutInflater.from(parent.context)
                .inflate(R.layout.layout_load_state_view, parent, false)
        )
    }

    class LoadStateViewHolder(private val view: View) : RecyclerView.ViewHolder(view)
}

Dao

@Query("SELECT * FROM notifications ORDER BY createdAt DESC LIMIT :size")
fun fetchNotifications(size: Int): List