Android 回收器视图中不显示房间数据库中的数据。可能有什么问题？

我想通过RoomDatabase在回收器视图中显示我的物品。但当我启动应用程序时，它会显示只有标题的空屏幕

它是回收器视图的适配器

class AlarmAdapter : ListAdapter<Alarm, AlarmAdapter.AlarmHolder>(DIFF_CALLBACK) {
    private lateinit var alarmViewModel: AlarmViewModel
    companion object {
        private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<Alarm>() {
            override fun areItemsTheSame(oldItem: Alarm, newItem: Alarm): Boolean {
                return oldItem.id == newItem.id
            }
            override fun areContentsTheSame(oldItem: Alarm, newItem: Alarm): Boolean {
                return oldItem.days == newItem.days && oldItem.timeInMinutes == newItem.timeInMinutes
                        && oldItem.departTimeInMinutes == newItem.departTimeInMinutes && oldItem.fromAddress == newItem.fromAddress
                        && oldItem.toAddress == newItem.toAddress && oldItem.isEnabled == newItem.isEnabled
            }
        }
    }
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): AlarmHolder {
        val itemView = LayoutInflater.from(parent.context)
            .inflate(R.layout.alarm_item, parent, false)
        alarmViewModel = ViewModelProviders.of(parent.context as FragmentActivity).get(AlarmViewModel::class.java)
        return AlarmHolder(itemView)
    }
    override fun onBindViewHolder(holder: AlarmHolder, position: Int) {
        val currentAlarm = getItem(position)
        holder.fromAddress.text = currentAlarm.fromAddress
        // and other texts
        holder.alarmSwitch.isEnabled = currentAlarm.isEnabled
        holder.alarmSwitch.setOnClickListener {
            holder.alarmSwitch.toggle()
            currentAlarm.isEnabled = !currentAlarm.isEnabled
            alarmViewModel.update(currentAlarm)
        }
    }
    inner class AlarmHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        internal var fromAddress = itemView.findViewById<TextView>(R.id.alarm_item_from_address)
        // and other resources
    }
}

它是一个存储库

class AlarmRepository(application: Application) {
    private var alarmDao: AlarmDao
    private var allAlarms: LiveData<List<Alarm>>

    private val uiScope = CoroutineScope(Dispatchers.IO)

    init {
        val database: AlarmDatabase = AlarmDatabase.getInstance(application.applicationContext)!!
        alarmDao = database.alarmDao()
        allAlarms = alarmDao.getAllAlarms()
    }

    fun getAllAlarms() = allAlarms

    fun insert(alarm: Alarm) {
        uiScope.launch { alarmDao.insert(alarm) }
    }

    fun delete(alarm: Alarm) {
        uiScope.launch { alarmDao.delete(alarm) }
    }

    fun deleteAllNotes() {
        uiScope.launch { alarmDao.deleteAllAlarms() }
    }

    fun update(alarm: Alarm) {
        uiScope.launch { alarmDao.update(alarm) }
    }

    fun getAlarmById(id: Int) = alarmDao.getAlarmById(id)
}

还有刀类

@Dao
interface AlarmDao {

    @Insert
    fun insert(alarm: Alarm)

    @Delete
    fun delete(alarm: Alarm)

    @Update
    fun update(alarm: Alarm)

    @Query("DELETE FROM alarm_table")
    fun deleteAllAlarms()

    @Query("SELECT * FROM alarm_table ORDER BY days ASC")
    fun getAllAlarms() : LiveData<List<Alarm>>

    @Query("SELECT * FROM alarm_table WHERE id = :id")
    fun getAlarmById(id: Int) : Alarm
}

我能做些什么来解决这个问题？

---

如果你需要更多的代码，请告诉我

在AlarmViewModel类中，将对repo的调用放在getAllAlarms方法中

fun getAllAlarms() {
   repository.getAllAlarms()
}

将其从init方法中删除

allAlarms = alarmDao.getAllAlarms()

放

fun getAllAlarms() = alarmDao.getAllAlarms()

---

你能把你的AlarmViewModel类、存储库和dao类放在一起吗？@joao86的课程问题：-你在哪里做adapter.notifyDataSetChanged？-在观察者内部，it变量是否有报警列表？@joao86 adapter.submitlisit包含关于更改的通知。在《观察家》里面，是艾姆提，它没有帮助我

allAlarms = alarmDao.getAllAlarms()

fun getAllAlarms() = alarmDao.getAllAlarms()