ROOM: how to display one to many relation data into recyclerview using lifecycle

Question

I've tried to display the join data from two entity into the recyclerview. However, when I add new data that has the same idBarang (FK) as the old data that has the same idBarang, recyclerview display the same data row.

This is the code snippet:

ENTITY

@Entity(
    foreignKeys = [
        ForeignKey(entity = Item::class, parentColumns = ["id"], childColumns = ["id_barang"])
    ],
    indices = [Index("id_barang")]
)
data class Purchaseorder(
    @PrimaryKey(autoGenerate = true)
    val id: Int = 0,
    @ColumnInfo(name = "no_po")
    val noPO: String,
    @ColumnInfo(name = "id_barang")
    val idBarang: Int,
    @ColumnInfo(name = "tanggal_po")
    val tanggalPO: String,
    @ColumnInfo(name = "jumlah_po")
    val jumlahPO: Int,
    @ColumnInfo(name = "harga_po")
    val hargaPO: Double
)

@Entity
data class Item(
    @PrimaryKey(autoGenerate = true)
    val id: Int = 0,
    @ColumnInfo(name = "kode_barang")
    val kodeBarang: String,
    @ColumnInfo(name = "nama")
    val namaBarang: String,
    @ColumnInfo(name = "min_stok")
    val minStok: Int,
    val stok: Int,
    val unit: String
)

data class PurchaseorderAndItem(
    @Embedded val item: Item,
    @Relation(
        parentColumn = "id",
        entityColumn = "id_barang"
    )
    val purchaseorder : List<Purchaseorder>,
//    val purchaseorder : Purchaseorder,
)
/**
 * Returns the passed in price in currency format.
 */
fun Purchaseorder.getFormattedPrice(): String =
    NumberFormat.getCurrencyInstance().format(hargaPO)

fun Purchaseorder.getUnitPrice(): String =
    NumberFormat.getCurrencyInstance().format(hargaPO/jumlahPO)

fun Purchaseorder.getLongDate() : String {
    val month = arrayOf("Januari","Februari","Maret","April","Mei","Juni","Juli","Agustus","September","Oktober","November","Desember")
    val dateTemp = tanggalPO.split("/")


    return dateTemp[0] + " " +month[dateTemp[1].toInt()-1] + " " +dateTemp[2]
}

DAO

@Dao
interface PurchaseorderDao {
    @Transaction
    @Query("SELECT * from purchaseorder as po INNER JOIN item ON item.id = po.id_barang WHERE po.id = :id")
    fun retrievePurchaseorder(id: Int): Flow<PurchaseorderAndItem>

    @Transaction
    @Query("SELECT * FROM purchaseorder as po INNER JOIN item ON item.id = po.id_barang ORDER BY po.id DESC")
    fun getPurchaseorders(): Flow<List<PurchaseorderAndItem>>
}

VIEWMODEL

class PurchaseorderViewModel(private val purchaseorderDao: PurchaseorderDao) : ViewModel() {

    var allPurchaseorders: LiveData<List<PurchaseorderAndItem>> = purchaseorderDao.getPurchaseorders().asLiveData()

    fun retrievePurchaseorder(id: Int): LiveData<PurchaseorderAndItem> {
        return purchaseorderDao.retrievePurchaseorder(id).asLiveData()
    }

    ...

class PurchaseorderViewModelFactory(
    private val purchaseorderDao: PurchaseorderDao
) : ViewModelProvider.Factory {
    override fun <T : ViewModel> create(modelClass: Class<T>): T {
        if (modelClass.isAssignableFrom(PurchaseorderViewModel::class.java)) {
            @Suppress("UNCHECKED_CAST")
            return PurchaseorderViewModel(purchaseorderDao) as T
        }
        throw IllegalArgumentException("Unknown ViewModel class")
    }
}

LIST FRAGMENT

class PurchaseorderListFragment : Fragment() {
    private val viewModel: PurchaseorderViewModel by activityViewModels {
        PurchaseorderViewModelFactory(
            (activity?.application as InventoryApplication).database.purchaseorderDao(),
        )
    }

    private var _binding: FragmentPurchaseorderListBinding? = null
    private val binding get() = _binding!!

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



    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        val adapter = PurchaseorderListAdapter {
            val action =
                PurchaseorderListFragmentDirections.actionPurchaseorderListFragmentToPurchaseorderDetailFragment(it.purchaseorder[0].id)
            this.findNavController().navigate(action)
        }

        binding.recyclerViewPurchaseorder.layoutManager = object : LinearLayoutManager(this.context) {
            override fun checkLayoutParams(lp: RecyclerView.LayoutParams): Boolean {
                lp.width = width
                return true
            }


        }
        binding.recyclerViewPurchaseorder.adapter = adapter
        viewModel.allPurchaseorders.observe(this.viewLifecycleOwner) { purchaseorder ->
            purchaseorder.let {
                adapter.submitList(it)
            }
        }


        binding.floatingActionButton.setOnClickListener {
            val action = PurchaseorderListFragmentDirections.actionPurchaseorderListFragmentToAddPurchaseorderFragment(
                getString(R.string.add_fragment_title)
            )
            this.findNavController().navigate(action)
        }
    }
}

LIST ADAPTER

class PurchaseorderListAdapter(private val onPurchaseorderClicked: (PurchaseorderAndItem) -> Unit) :
    ListAdapter<PurchaseorderAndItem, PurchaseorderListAdapter.PurchaseorderViewHolder>(DiffCallback) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PurchaseorderViewHolder {
        return PurchaseorderViewHolder(
            PurchaseorderListItemBinding.inflate(
                LayoutInflater.from(
                    parent.context
                )
            )
        )
    }

    override fun onBindViewHolder(holder: PurchaseorderViewHolder, position: Int) {
        val current = getItem(position)
        holder.itemView.setOnClickListener {
            onPurchaseorderClicked(current)
        }
        holder.bind(current)
    }

    class PurchaseorderViewHolder(private var binding: PurchaseorderListItemBinding) :
        RecyclerView.ViewHolder(binding.root) {

        fun bind(purchaseorder: PurchaseorderAndItem) {

            val purchaseorders = purchaseorder.purchaseorder[0]
            val item = purchaseorder.item
            binding.rvNamaBarangNNoPO.text = binding.rvNamaBarangNNoPO.context.getString(R.string.kode_cate,item.namaBarang,purchaseorders.noPO)
            binding.rvHargaPO.text = purchaseorders.getFormattedPrice()
            binding.rvJumlahPO.text = purchaseorders.jumlahPO.toString()
            binding.rvTanggalPO.text = purchaseorders.tanggalPO

//            Log.i("ininya: ", purchaseorder)
        }
    }

    companion object {
        private val DiffCallback = object : DiffUtil.ItemCallback<PurchaseorderAndItem>() {

            override fun areItemsTheSame(
                oldItem: PurchaseorderAndItem,
                newItem: PurchaseorderAndItem,
            ): Boolean {
                return oldItem.purchaseorder[0].id == newItem.purchaseorder[0].id
            }

            override fun areContentsTheSame(
                oldItem: PurchaseorderAndItem,
                newItem: PurchaseorderAndItem,
            ): Boolean {
                return oldItem.purchaseorder[0].noPO == newItem.purchaseorder[0].noPO
            }

        }
    }
}

XML RECYCLER ROW

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:weightSum="5.7">
    <TextView
        android:id="@+id/rv_namaBarang_N_noPO"
        style="@style/Widget.Inventory.ListItemTextView"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:layout_weight="2"
        android:fontFamily="sans-serif"
        tools:text="Terigu (P001)" />

    <TextView
        android:id="@+id/rv_tanggalPO"
        style="@style/Widget.Inventory.ListItemTextView"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:layout_weight="1.2"
        android:layout_marginHorizontal="@dimen/margin_between_elements"
        android:fontFamily="sans-serif-medium"
        android:textAlignment="textStart"
        tools:text="21/12/2022" />

    <TextView
        android:id="@+id/rv_jumlahPO"
        style="@style/Widget.Inventory.ListItemTextView"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:layout_weight="1"
        android:fontFamily="sans-serif-medium"
        android:textAlignment="textEnd"
        tools:text="100Kg" />
    <TextView
        android:id="@+id/rv_hargaPO"
        style="@style/Widget.Inventory.ListItemTextView"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:layout_weight="1.5"
        android:fontFamily="sans-serif-medium"
        android:textAlignment="textEnd"
        tools:text="110.000.000" />
</LinearLayout>