如何在 Kotlin 的 android 房间数据库中获取插入行的 ID？

Question

我正在尝试从最新用户那里获取用户 ID。如何在自动生成 ID 时让插入方法吐出 ID？

模型

@PrimaryKey(autoGenerate = true)
    val userId: Int

在道中

@Insert(onConflict = OnConflictStrategy.REPLACE)
   fun addUserWithLong(user: User): LiveData<Long>

在存储库中

fun addUserWitLong(user: User): LiveData<Long> {
        return userDao.addUserWithLong(user)
    }

在 ViewModel 中

fun addUserWithLong(user: User): LiveData<Long> {
        return repository.addUserWitLong(user)
    }

在片段中

val id: Long? = userViewModel.addUserWithLong(user).value

我在文档中读到 @Insert returns Long 作为行 ID，但我不知道如何对其进行编程。现在错误是“不确定如何处理插入方法 return 类型。”有什么方法可以用 LiveData 而不是用 Rxjava 来制作。那是不需要下载更多的依赖项。

Answer 1

根据文档here

If the @Insert method receives a single parameter, it can return a long value, which is the new rowId for the inserted item. If the parameter is an array or a collection, then the method should return an array or a collection of long values instead, with each value as the rowId for one of the inserted items. To learn more about returning rowId values, see the reference documentation for the @Insert annotation, as well as the SQLite documentation for rowid tables

所以你可以像这样使用它

   @Insert(onConflict = OnConflictStrategy.REPLACE)
   long addUserWithLong(user: User)

或者如果您要插入列表

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    long[] addUserWithLong(user: List<User>)

编辑-1

检查 post.

的答案后

No, you can't. I wrote an answer to the issue. The reason is, that LiveData is used to notify for changes. Insert, Update, Delete won't trigger a change.

我刚刚创建了一个测试项目，并成功收到了 activity 中最后插入的项目的 ID。这是我的实现。

道

@Insert
suspend fun addUser(user: Users): Long

回购

suspend fun insertUser(context: Context, users: Users): Long {
        val db = AppDatabase.getInstance(context)
        val dao = db.userDao()
        return dao.addUser(users)
    }

ViewModel

 fun addUser(context: Context, users: Users) = liveData {
//you can also emit your customized object here. 
        emit("Inserting...")
        try {
            val userRepo = UsersRepo()
            val response = userRepo.insertUser(context, users)
            emit(response)
        } catch (e: Exception) {
            e.printStackTrace()
            emit(e.message)
        }
    }

Activity

viewModel.addUser(applicationContext, user).observe(this, Observer { userId ->
            Log.d("MainActivity", "Inserted User Id is $userId")
        })

检查测试应用程序 here.

如何在 Kotlin 的 android 房间数据库中获取插入行的 ID？

How to get the id of inserted row in android room databse in Kotlin?

android

kotlin

android-room

android-livedata