如何通过VIEWMODEL从数据库（MODEL）中的Activity（VIEW）获取添加的对象的ID。Android，MVVM

• 我有一个基于MVVM体系结构Android的ShoppingList App 。
• 我没有做到，但是我遵循了有关YouTube的教程。
• 这是显示购物清单的app（1/2）的图像。右下角是用于添加列表的新元素的按钮。

• 这是第二个视图（2/2），其中出现对话框以输入元素的名称和数量。在这里，我们有取消按钮和添加按钮。

The problem is when I click the ADD button on the Dialog Box I do not know how to get an ID of this added item to the recycler view on my VIEW and to make it appear via the TOAST command on my main Activity.

The question is - How to get an ID of a new added element to my shopping list and show it on my MainActivity(ShoppingActivity) VIEW when I click the ADD button?

If you need additional information ask me out immediately! I will provide you anything you need.

Code is provided here:

ShoppingActivity(View)

class ShoppingActivity : AppCompatActivity(), KodeinAware {
override val kodein by kodein()
private val factory: ShoppingViewModelFactory by instance()

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_shopping)

    // View Model is being created out of other classes to set changes to View

    val viewModel =  ViewModelProviders.of(this, factory).get(ShoppingViewModel::class.java)

    // Adapters and Recycler View

    val adapter = ShoppingItemAdapter(listOf(), viewModel)
    rvShoppingItems.layoutManager = LinearLayoutManager(this)
    rvShoppingItems.adapter = adapter


    // ViewModel makes changes to the Activity

    viewModel.getAllShoppingItems().observe(this, Observer {
        adapter.items = it
        adapter.notifyDataSetChanged()
    })

    fab.setOnClickListener {
        AddShoppingItemDialog(this ,
            object: AddDialogListener{
                override fun onAddButtonClicked(item: ShoppingItem) {
                    viewModel.upsert(item)
                    showToast(viewModel.getID(item).toString().toInt())

                }
            }).show()
    }

}

fun showToast(id: Int) {
    Toast.makeText(this@ShoppingActivity, "ID записи: $id", Toast.LENGTH_LONG).show()
}}

ShoppingViewModel(ViewModel)

class ShoppingViewModel(private val repository: ShoppingRepository): ViewModel() {

fun upsert(item: ShoppingItem) = CoroutineScope(Dispatchers.IO).launch {
    repository.upsert(item)
}

fun delete(item: ShoppingItem) = CoroutineScope(Dispatchers.IO).launch {
    repository.delete( item)
}

fun getID(item: ShoppingItem) = repository.getID(item)


fun getAllShoppingItems() = repository.getAllShoppingItems()

}

AddShoppingItemDialog(the logic of showing Dialog info)

class AddShoppingItemDialog(context: Context, var addDialogListener: AddDialogListener): AppCompatDialog(context)  {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.dialog_add_shopping_item)

    tvAdd.setOnClickListener {
        val name = etName.text.toString()
        val amount = etAmount.text.toString()

        if(name.isEmpty()) {
            Toast.makeText(context, "Please enter the name", Toast.LENGTH_LONG).show()

            return@setOnClickListener
        }

        if(amount.isEmpty()) {

            Toast.makeText(context, "Please enter the amount", Toast.LENGTH_LONG).show()

            return@setOnClickListener
        }

        val item = ShoppingItem(name, amount.toInt())

        // We need to

        addDialogListener.onAddButtonClicked(item)
        dismiss()
    }

    tvCancel.setOnClickListener {
        cancel()
    }
}}

Repository

class ShoppingRepository(private val db: ShoppingDatabase) {

suspend fun upsert(item: ShoppingItem) = db.getShoppingDao().upsert(item)
suspend fun delete(item: ShoppingItem) = db.getShoppingDao().delete(item)
fun getID(item: ShoppingItem) = db.getShoppingDao().getID(item)

fun getAllShoppingItems() = db.getShoppingDao().getAllShoppingItems()}

ShoppingDAO

@Dao
interface ShoppingDao {

@Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun upsert(item: ShoppingItem) : Long

@Delete
suspend fun delete(item: ShoppingItem)

@Query("SELECT * FROM shopping_items WHERE id = $CURRENT_POSITION")
fun getID(item: ShoppingItem): LiveData<Int>

@Query("SELECT * FROM shopping_items")
fun getAllShoppingItems(): LiveData<List<ShoppingItem>>
}

ShoppingItem

const val CURRENT_POSITION = 0

@Entity(tableName = "shopping_items")

data class ShoppingItem(


@ColumnInfo(name = "item_name")
var name: String,
@ColumnInfo(name = "item_amount")
var amount: Int
) {

@PrimaryKey(autoGenerate = true)
var id: Int? = CURRENT_POSITION


}

AddDialogListener

interface AddDialogListener {

fun onAddButtonClicked(item: ShoppingItem)

}

App View with added items