android - 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

Question

我有一个基于 MVVM体系结构Android 构建的ShoppingList应用程序。

我没有做到，但我遵循了有关YouTube的教程。

这是显示购物 list 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 View (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。

问题是，当我单击对话框上的 ADD按钮时，我不知道如何在VIEW的“回收者” View 中获取此添加项的ID，并使其通过我的主Activity上的TOAST命令显示。
问题是- ，当我单击“添加”按钮时，如何获取新添加的元素的ID到我的购物 list 中并将其显示在MainActivity(ShoppingActivity)VIEW中？
如果您需要其他信息，请立即联系我!我会为您提供所需的任何东西。
此处提供代码:
ShoppingActivity(查看)

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(显示对话框信息的逻辑)

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()
    }
}}

存储库

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()}

购物DAO

@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>>
}

购物商品

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)

}
已添加项目的App View

Answer 1

由于对数据库的插入/向上插入操作是挂起函数，因此请在 View 模型中观察返回的id
用ShoppingViewModel

private var _itemId : Long = MutableLiveData<Long>()
val itemId : LiveData<Long>
get() = _itemId

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

在 ShoppingActivity中，

viewModel.itemId.observe(this, Observer {id ->
    showToast(id)

})

如果您需要了解更多详细信息，请告诉我。