Android sometimes fails to detect iBeacon devices

Question

I am using https://github.com/AltBeacon/android-beacon-library library to detect iBeacon. But sometimes RangingBeacons returns zero.

My application runs as follows:

Call startRangingBeacons to detect the iBeacon. After getting the beacon, call stopRangingBeacons.

And User can call startRangingBeacons function again to detect other iBeacon.

This is the case quite often. Sometimes after a few seconds the detection can return to normal, but sometimes nothing can be detected.

class EllaBeaconManger(context: Context) : MonitorNotifier {
    private var currentContext: Context = context
    private val mBeaconManager: BeaconManager = BeaconManager.getInstanceForApplication(context)
    private val mRegion: Region = Region("*Masked*", Identifier.parse("*Masked*"), null, null)
    var didDetectElla: ((deviceId: String) -> Unit)? = null
    private var canFindBeacon: Boolean = false
    lateinit var activity: MainActivity

    // I don't know why but when I call startBeacon again,
    // the library will sometimes return the result that the Beacon was previously connected.
    private var count = 0

    companion object : SingletonHolder<EllaBeaconManger, Context>(::EllaBeaconManger)
    private val rangingObserver = Observer<Collection<Beacon>> { beacons ->
        if (BeaconManager.getInstanceForApplication(context).rangedRegions.isNotEmpty()) {
            if(beacons.isNotEmpty()) {
                for (beacon in beacons) {
                    val statusBeacon = EllaManager.shared.deviceIdByMajor(beacon.id2.toInt())
                    if (statusBeacon != null && statusBeacon == EllaStatus.UNAUTHORIZED) {
                        if (beacon.distance <= 1.0 && !canFindBeacon && count >= 1) {
                            stopBeacon()
                            val deviceId = EllaManager.shared.deviceId(beacon.id2.toInt(), beacon.id3.toInt(), EllaManager.environment)
                            didDetectElla?.invoke(deviceId)
                        } else {
                            count++
                        }
                    }
                }
            }
        }
    }

    fun initBeacon() {
        mBeaconManager.beaconParsers.clear()
        mBeaconManager.beaconParsers.add(BeaconParser().setBeaconLayout("m:0-3=4c000215,i:4-19,i:20-21,i:22-23,p:24-24"))

        // Set up a Live Data observer for beacon data
        val regionViewModel = mBeaconManager.getRegionViewModel(mRegion)

        // observer will be called each time a new list of beacons is ranged (typically ~1 second in the foreground)
        regionViewModel.rangedBeacons.observe(activity, rangingObserver)
    }

    fun startBeacon() {
        canFindBeacon = false
        count = 0
        mBeaconManager.startRangingBeacons(mRegion)
    }

    fun stopBeacon() {
        canFindBeacon = true
        count = 0
        mBeaconManager.stopRangingBeacons(mRegion)
    }

    override fun didEnterRegion(region: Region?) {
        if (region != null) {
            Log.d("ToiHK", "I detected a beacon in the region with namespace id " + region.id1 +
                    " and instance id: " + region.id2
            )
        }
    }

    override fun didExitRegion(region: Region?) {
        Log.d("ToiHK", "I Exit a beacon in the region with namespace id " + region?.id1 +
                " and instance id: " + region?.id2
        )
    }

    override fun didDetermineStateForRegion(state: Int, region: Region?) {
        Log.d("ToiHK", "I State $state a beacon in the region with namespace id " + region?.id1 +
                " and instance id: " + region?.id2
        )
    }
}