Scan failed: a BLE scan with the same settings is already started by the app

Expected behavior

No error in logs about scan already started

Actual behavior

@paulpv: “I am confused by the behavior that I am seeing when I background the app while a scan is active. With a scan active/started, I background the app and almost immediately get this…”

2020-01-28 14:50:21.042 17590-17590/org.altbeacon.beaconreference D/CycledLeScanner: Done with scan cycle
2020-01-28 14:50:21.044 17590-17590/org.altbeacon.beaconreference D/CycledLeScanner: Not stopping scan because this is Android N and we keep scanning for a minimum of 6 seconds at a time. We will stop in 3773 millisconds.
2020-01-28 14:50:21.045 17590-17590/org.altbeacon.beaconreference D/CycledLeScanner: starting a new scan cycle
2020-01-28 14:50:21.045 17590-17590/org.altbeacon.beaconreference D/CycledLeScanner: restarting a bluetooth le scan
2020-01-28 14:50:21.047 17590-17590/org.altbeacon.beaconreference D/CycledLeScannerForLollipop: starting a scan in SCAN_MODE_LOW_LATENCY
2020-01-28 14:50:21.049 17590-17590/org.altbeacon.beaconreference D/CycledLeScannerForLollipop: Using a wildcard scan filter on Samsung because the screen is on.  We will switch to a non-empty filter if the screen goes off

The log says it isn’t going to stop the scan, but what it does is start a scan while a scan is already scanning, which results in onScanFailed SCAN_FAILED_ALREADY_STARTED the the following log:

2020-01-28 14:58:50.950 17590-17590/org.altbeacon.beaconreference E/CycledLeScannerForLollipop: Scan failed: a BLE scan with the same settings is already started by the app

I have yet to find a way to get startAndroidOBackgroundScan to be called. 😕

Steps to reproduce this behavior

Run the reference app on a Samsung device with the screen on

Mobile device model and OS version

Samsung

Android Beacon Library version

2.16.4

[davidgyoung]

Yes, a BeaconParser is a requirement for getting background detections with this library. The setNonBeaconLeScanCallback is provided as a convenience method for apps that also need non-beacon BLE detections, so they apps don’t have to set up secondary beacon scanning. But this is a secondary function of the library provided only for convenience, and is certainly not a core function.

[paulpv]

I am using setNonBeaconLeScanCallback and clearing all beacon parsers. I get scan results for everything except when the screen is off. I do understand that scanning w/ the screen off is tricking on some phone brands and may need a special non-wildcard filter.

I can and will create a parser for my own BLE device, which isn’t always a beacon, but thought I would avoid that for now and just try to prove out if this library meets my requirements. If it is a requirement of this library to provide a valid beacon parser then I will go ahead and create a custom one.