android - 房间数据库 : inserted ID is always 0

Question

我正在尝试创建一个列表项的 Room 数据库。我在这里遵循示例:https://medium.com/mindorks/room-kotlin-android-architecture-components-71cad5a1bb35

这是我的数据类:

@Entity(tableName = "itemData")
data class ItemData(@PrimaryKey(autoGenerate = true) var id: Long? = null,
                    @ColumnInfo(name = "text") var text: String,
                    @ColumnInfo(name = "checked") var checked: Boolean

)

DAO:

@Dao
interface ItemDataDAO {

    @Insert(onConflict = REPLACE)
    fun insert(itemData: ItemData) : Long
}

数据库:

@Database(entities = arrayOf(ItemData::class), version = 1)
abstract class ItemDatabase() : RoomDatabase() {


    abstract fun itemDataDao(): ItemDataDAO

    companion object {
        private var INSTANCE: ItemDatabase? = null

        fun getInstance(context: Context): ItemDatabase? {
            if (INSTANCE == null) {
                synchronized(ItemDatabase::class) {
                    INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
                            ItemDatabase::class.java, "items.db")
                            .build()
                }
            }
            return INSTANCE
        }

        fun destroyInstance() {
            INSTANCE = null
        }
    }
}

工作线程:

class DbWorkerThread(threadName: String) : HandlerThread(threadName) {

    private lateinit var mWorkerHandler: Handler

    override fun onLooperPrepared() {
        super.onLooperPrepared()
        mWorkerHandler = Handler(looper)
    }

    fun postTask(task: Runnable) {
        mWorkerHandler.post(task)
    }
}

这是调用插入函数的监听器:

editText.setOnEditorActionListener { v, actionId, event ->
    return@setOnEditorActionListener when (actionId) {
        EditorInfo.IME_ACTION_DONE -> {
            createItem(editText)
            true
        }
        else -> false
    }
}

这是插入项目时调用的函数:

fun createItem(editText: EditText) {
    var text = editText.text.toString().trim()
    var itemData = ItemData(text = text, checked = false)
    var id : Long? = 0
    val task = Runnable {
        id = mDb?.itemDataDao()?.insert(itemData)
        println("inserted $id")
    }
    mDbWorkerThread.postTask(task)
}

但 ID 始终为 0，因此只会插入一项。任何人都可以看到问题吗？

我也曾尝试删除 id 的默认 null 值，但结果相同。

Answer 1

以下更改解决了该问题。

而不是像这样调用构造函数

var itemData = ItemData(text = text, checked = false)

我调用了默认的构造函数，构造完之后再设置参数。

var itemData = ItemData()
itemData.text = text
itemData.checked = false

这需要 ItemData 实体的以下构造函数:

constructor():this(null,"",false)