Android 在Observer内部使用AlarmManager会导致只调用一次observe（）

我已经为一个报警应用程序实现了一个MVVM体系结构，该应用程序带有一个切换按钮，当报警打开时激活报警，当报警关闭时停用报警。单击ToggleButton调用ViewModel中的函数，该函数基于ToggleButton的切换状态，通过将值设置为带有报警信息的LiveData来激活或禁用报警

在片段中，我从ViewModel观察LiveData，并通过使用AlarmManager调度PendingEvent来设置警报，或者通过取消PendingEvent和AlarmManager来取消警报。问题是，当我第一次启动应用程序时，第一次单击ToggleButton会触发片段中的观察者，但此后，即使LiveData值发生更改，观察者也会拒绝触发

我发现，删除AlarmManager相关的函数（setExactAndAllowHileId（）/cancel（））会使观察者每次都被触发，但添加这些函数会使观察者不再对任何LiveData更改做出反应

我认为最好用代码和日志来解释

AlarmViewModel.kt

private val newToast: MutableLiveData<SingleEvent<String>> = MutableLiveData()
private val activateEvent: MutableLiveData<SingleEvent<AlarmData>> = MutableLiveData()
private val deactivateEvent: MutableLiveData<SingleEvent<AlarmData>> = MutableLiveData()
...
private fun activateAlarm(alarmData: AlarmData) {
    newToast.value = SingleEvent("Alarm has been set!")
    activateEvent.value = SingleEvent(alarmData)
}

private fun deactivateAlarm(alarmData: AlarmData) {
    newToast.value = SingleEvent("Alarm has been cleared")
    deactivateEvent.value = SingleEvent(alarmData)
}
...
fun observeNewToast(): LiveData<SingleEvent<String>> = newToast
fun observeActivateEvent(): LiveData<SingleEvent<AlarmData>> = activateEvent
fun observeDeactivateEvent(): LiveData<SingleEvent<AlarmData>> = deactivateEvent

但是，如果我删除AlarmManager相关代码，观察者将一直被调用，正如预期的那样

修改的AlarmFragment.kt

@Inject
lateinit var alarmManager: AlarmManager
private val viewModel: SingleAlarmViewModel by lazy {
    ViewModelProviders.of(activity!!).get(AlarmViewModel::class.java)
}
private lateinit var newToastObserver: Observer<SingleEvent<String>>
private lateinit var activateEventObserver: Observer<SingleEvent<AlarmData>>
private lateinit var deactivateEventObserver: Observer<SingleEvent<AlarmData>>
...
override fun onResume() {
    super.onResume()

    newToastObserver = Observer {
        it?.getContentIfNotHandled()?.let { toastText ->
            info("observeNewToast() -> message: $toastText")
            Toast.makeText(activity, toastText, Toast.LENGTH_SHORT).show()
        }
    }

    activateEventObserver = Observer {
        it?.getContentIfNotHandled()?.let { alarmData ->
            info("activateEventObserver -> $alarmData")

            val idInteger = alarmData.timeInMillis.toInt()
            val alarmTime = alarmData.timeInMillis

            val activateAlarmIntent = Intent(activity, AlarmReceiver::class.java)
            activateAlarmIntent.putExtra("message", alarmData.toString())
            val pendingIntent = PendingIntent.getBroadcast(
                activity,
                idInteger,
                activateAlarmIntent,
                PendingIntent.FLAG_UPDATE_CURRENT
            )
            AlarmManagerCompat.setExactAndAllowWhileIdle(
                alarmManager,
                AlarmManager.RTC_WAKEUP,
                alarmTime,
                pendingIntent
            )
        }
    }

    deactivateEventObserver = Observer {
        it?.getContentIfNotHandled()?.let { alarmData ->
            info("deactivateEventObserver -> $alarmData")

            val idInteger = alarmData.timeInMillis.toInt()

            val deactivateAlarmIntent = Intent(activity, AlarmReceiver::class.java)
            deactivateAlarmIntent.putExtra("message", alarmData.toString())
            val pendingIntent = PendingIntent.getBroadcast(
                activity,
                idInteger,
                deactivateAlarmIntent,
                PendingIntent.FLAG_UPDATE_CURRENT
            )
            pendingIntent.cancel()
            alarmManager.cancel(pendingIntent)
        }
    }
    viewModel.observeNewToast().observe(activity!!, newToastObserver)
    viewModel.observeActivateEvent().observe(activity!!, activateEventObserver)
    viewModel.observeDeactivateEvent().observe(activity!!, deactivateEventObserver)
}

override fun onPause() {
    super.onPause()
    viewModel.apply {
        observeNewToast().removeObserver(newToastObserver)
        observeActivateEvent().removeObserver(activateEventObserver)
        observeDeactivateEvent().removeObserver(deactivateEventObserver)
    }
}

@Inject
lateinit var alarmManager: AlarmManager
private val viewModel: SingleAlarmViewModel by lazy {
    ViewModelProviders.of(activity!!).get(AlarmViewModel::class.java)
}
private lateinit var newToastObserver: Observer<SingleEvent<String>>
private lateinit var activateEventObserver: Observer<SingleEvent<AlarmData>>
private lateinit var deactivateEventObserver: Observer<SingleEvent<AlarmData>>
...
override fun onResume() {
    super.onResume()

    newToastObserver = Observer {
        it?.getContentIfNotHandled()?.let { toastText ->
            info("observeNewToast() -> message: $toastText")
            Toast.makeText(activity, toastText, Toast.LENGTH_SHORT).show()
        }
    }

    activateEventObserver = Observer {
        it?.getContentIfNotHandled()?.let { alarmData ->
            info("activateEventObserver -> $alarmData")

            val idInteger = alarmData.timeInMillis.toInt()
            val alarmTime = alarmData.timeInMillis

            val activateAlarmIntent = Intent(activity, AlarmReceiver::class.java)
            activateAlarmIntent.putExtra("message", alarmData.toString())
            val pendingIntent = PendingIntent.getBroadcast(
                activity,
                idInteger,
                activateAlarmIntent,
                PendingIntent.FLAG_UPDATE_CURRENT
            )

            // AlarmManager code commented out
            // AlarmManagerCompat.setExactAndAllowWhileIdle(
            //     alarmManager,
            //     AlarmManager.RTC_WAKEUP,
            //     alarmTime,
            //     pendingIntent
            // )
        }
    }

    deactivateEventObserver = Observer {
        it?.getContentIfNotHandled()?.let { alarmData ->
            info("deactivateEventObserver -> $alarmData")

            val idInteger = alarmData.timeInMillis.toInt()

            val deactivateAlarmIntent = Intent(activity, AlarmReceiver::class.java)
            deactivateAlarmIntent.putExtra("message", alarmData.toString())
            val pendingIntent = PendingIntent.getBroadcast(
                activity,
                idInteger,
                deactivateAlarmIntent,
                PendingIntent.FLAG_UPDATE_CURRENT
            )
            pendingIntent.cancel()

            // AlarmManager code commented out
            // alarmManager.cancel(pendingIntent)
        }
    }
    viewModel.observeNewToast().observe(activity!!, newToastObserver)
    viewModel.observeActivateEvent().observe(activity!!, activateEventObserver)
    viewModel.observeDeactivateEvent().observe(activity!!, deactivateEventObserver)
}

override fun onPause() {
    super.onPause()
    viewModel.apply {
        observeNewToast().removeObserver(newToastObserver)
        observeActivateEvent().removeObserver(activateEventObserver)
        observeDeactivateEvent().removeObserver(deactivateEventObserver)
    }
}

我已经尝试将ViewModel生命周期所有者设置为父活动，并将其设置回Fragment，但没有任何区别。删除AlarmManger相关的代码可以让观测者工作，但是由于我试图通过观测者设置警报，这让我非常沮丧。为什么AlarmManager让观察者在第一次之后停止被观察？它在什么地方被注销了吗

---

事先谢谢。

原来这是我犯的完全不同的错误。。我错误地忘记了将AlarmManager注入到我应该通过Dagger注入的特定片段中。

---

谢谢你的贡献

因此，您取消了

停用EventTobServer

中的警报。但您希望警报在同一时间段后再次运行吗？或者在取消后是否再次调用

activateEventObserver

。您可以调用

activateEventObserver

再次设置警报，无论是在同一时间还是另一时间。在这个应用程序中，我打算一次只激活一个警报。

@Inject
lateinit var alarmManager: AlarmManager
private val viewModel: SingleAlarmViewModel by lazy {
    ViewModelProviders.of(activity!!).get(AlarmViewModel::class.java)
}
private lateinit var newToastObserver: Observer<SingleEvent<String>>
private lateinit var activateEventObserver: Observer<SingleEvent<AlarmData>>
private lateinit var deactivateEventObserver: Observer<SingleEvent<AlarmData>>
...
override fun onResume() {
    super.onResume()

    newToastObserver = Observer {
        it?.getContentIfNotHandled()?.let { toastText ->
            info("observeNewToast() -> message: $toastText")
            Toast.makeText(activity, toastText, Toast.LENGTH_SHORT).show()
        }
    }

    activateEventObserver = Observer {
        it?.getContentIfNotHandled()?.let { alarmData ->
            info("activateEventObserver -> $alarmData")

            val idInteger = alarmData.timeInMillis.toInt()
            val alarmTime = alarmData.timeInMillis

            val activateAlarmIntent = Intent(activity, AlarmReceiver::class.java)
            activateAlarmIntent.putExtra("message", alarmData.toString())
            val pendingIntent = PendingIntent.getBroadcast(
                activity,
                idInteger,
                activateAlarmIntent,
                PendingIntent.FLAG_UPDATE_CURRENT
            )

            // AlarmManager code commented out
            // AlarmManagerCompat.setExactAndAllowWhileIdle(
            //     alarmManager,
            //     AlarmManager.RTC_WAKEUP,
            //     alarmTime,
            //     pendingIntent
            // )
        }
    }

    deactivateEventObserver = Observer {
        it?.getContentIfNotHandled()?.let { alarmData ->
            info("deactivateEventObserver -> $alarmData")

            val idInteger = alarmData.timeInMillis.toInt()

            val deactivateAlarmIntent = Intent(activity, AlarmReceiver::class.java)
            deactivateAlarmIntent.putExtra("message", alarmData.toString())
            val pendingIntent = PendingIntent.getBroadcast(
                activity,
                idInteger,
                deactivateAlarmIntent,
                PendingIntent.FLAG_UPDATE_CURRENT
            )
            pendingIntent.cancel()

            // AlarmManager code commented out
            // alarmManager.cancel(pendingIntent)
        }
    }
    viewModel.observeNewToast().observe(activity!!, newToastObserver)
    viewModel.observeActivateEvent().observe(activity!!, activateEventObserver)
    viewModel.observeDeactivateEvent().observe(activity!!, deactivateEventObserver)
}

override fun onPause() {
    super.onPause()
    viewModel.apply {
        observeNewToast().removeObserver(newToastObserver)
        observeActivateEvent().removeObserver(activateEventObserver)
        observeDeactivateEvent().removeObserver(deactivateEventObserver)
    }
}

02-20 18:44:18.207 24565-24565/com.aly.alarm I/AlarmFragment: observeNewToast() -> message: Alarm has been cleared
02-20 18:44:18.222 24565-24565/com.aly.alarm I/AlarmFragment: deactivateEventObserver -> AlarmData(id=1, timeInMillis=1550730780000, isToggledOn=true)
02-20 18:44:18.367 24565-24565/com.aly.alarm I/AlarmFragment: observeNewToast() -> message: Alarm has been set!
02-20 18:44:18.382 24565-24565/com.aly.alarm I/AlarmFragment: activateEventObserver -> AlarmData(id=1, timeInMillis=1550730780000, isToggledOn=true)
02-20 18:44:21.277 24565-24565/com.aly.alarm I/AlarmFragment: observeNewToast() -> message: Alarm has been cleared
02-20 18:44:21.297 24565-24565/com.aly.alarm I/AlarmFragment: deactivateEventObserver -> AlarmData(id=1, timeInMillis=1550730780000, isToggledOn=true)
02-20 18:44:22.177 24565-24565/com.aly.alarm I/AlarmFragment: observeNewToast() -> message: Alarm has been set!
02-20 18:44:22.197 24565-24565/com.aly.alarm I/AlarmFragment: activateEventObserver -> AlarmData(id=1, timeInMillis=1550730780000, isToggledOn=true)
02-20 18:44:22.842 24565-24565/com.aly.alarm I/AlarmFragment: observeNewToast() -> message: Alarm has been cleared
02-20 18:44:22.857 24565-24565/com.aly.alarm I/AlarmFragment: deactivateEventObserver -> AlarmData(id=1, timeInMillis=1550730780000, isToggledOn=true)
02-20 18:44:23.447 24565-24565/com.aly.alarm I/AlarmFragment: observeNewToast() -> message: Alarm has been set!