使用 DrawerLayout 时 viewLifecycleOwner 获取空值

Question

我的 Fragment 中有以下功能 -

private fun getOffenderInfo(device: BleDevice) {
        val offenderInfoRequest = OffenderInfoBody(activity?.sharedPreferences?.deviceId, activity?.sharedPreferences?.token, listOf(TagItem(device.tagID)))
        offenderViewModel.getOffenderInfo(offenderInfoRequest).observe(viewLifecycleOwner, { offenders ->
            when (offenders) {
                is Resource.Loading -> {
                }
                is Resource.Success -> {
                    updateUI(offenders.data, device)
                }
                is Resource.Exception -> {
                }
            }
        })
    }

这是由我找到一个 BLE 设备触发的 -

private fun initViews() {
        
        //.....Other not relevant code

        bleManager = BLEManager { bleDevice ->
            handleDeviceFound(bleDevice)
        }

    }

 // Handle BLE device found
    private fun handleDeviceFound(device: BleDevice) {
        // check if bleDevice with this TAG_ID already exist in bleDevices
        bleDevices.find { it.tagID == device.tagID } ?: return addDevice(device)
        if (device.bleOffender == null || device.bleOffender?.status == -1)
            return getOffenderInfo(device)
        val offenderDeviceData = tagDecryption.parseTagData(device, tagDecryption.decryptOffenderDetails(device))
        handleDeviceData(offenderDeviceData)
    }

    // adding new device to bleDevices & update adapter
    private fun addDevice(device: BleDevice) {
        bleDevices.add(device)
        tagsAdapter.addDevice(device)
        binding.fragmentScannerClearButton.isEnabled = bleDevices.isNotEmpty()
       return getOffenderInfo(device)


    }

并且在我的 ViewModel 中调用一个方法来访问本地和远程数据 -

 fun getOffenderInfo(offenderInfoBody: OffenderInfoBody) = liveData(Dispatchers.IO) {
        emit(Resource.Loading<Nothing>())
        emit(offenderRepository.getOffenderInfo(offenderInfoBody))
    }

问题是，当我在 BLE 扫描期间在我的 DrawerLayout 中的 Fragment 之间切换时，实时数据观察器开始转向，应用程序崩溃并出现以下错误

java.lang.IllegalStateException: Can't access the Fragment View's LifecycleOwner when getView() is null i.e., before onCreateView() or after onDestroyView()

Fragment 是可通过 DrawerLayout 访问的 3 个 fragment 之一。

如果我不在扫描期间，我可以毫无问题地切换。

据我所知，livedata 功能不应该导致这个问题，只是停止观察者，尽管它不会。

我错过了什么？

编辑-

我的 BLEManager class -

class BLEManager(private val onBleScanResult: (device: BleDevice) -> Unit) : BluetoothAdapter.LeScanCallback {

    override fun onLeScan(device: BluetoothDevice?, rssi: Int, scanRecord: ByteArray?) {
        if (scanRecord == null || device == null) return
        // siteCode validation indicates that tag is SuperCom tag
        val siteCode = scanRecord[5].toInt() and 0xFF
        val tagID: Int = (scanRecord[6].toInt() and 0xFF) + (scanRecord[7].toInt() and 0xFF) * 256 + (scanRecord[8].toInt() and 0xFF) * 65536
        // validate TagId isn't equals to 0
//            if (tagID != 0 && (tagID == 2467 || tagID == 3004)) { }// remove *&& (tagID == 2467 || tagID == 3004)* in production (used only for testing)
        if (tagID == 0) return
        val bleDevice = BleDevice(device = device, tagID = tagID.toString(), rssi = rssi, scanRecord = scanRecord)
        onBleScanResult(bleDevice)
    }
}

Answer 1

修复它的最简单方法是在片段被销毁时停止扫描

override fun onDestroyView() {
    super.onDestroyView()
    bleScanner.stopScan(bleManager)
}

使用 DrawerLayout 时 viewLifecycleOwner 获取空值

viewLifecycleOwner gets null value when working with DrawerLayout

android

android-fragments

android-livedata