onServicesDiscovered may not be handled correctly

[kovelo]

Android will call onServicesDiscovered multiple times as it is discovering a service and will only call it with a "Success" after it has finished fully discovering the service and all of its characteristics. This library incorrectly assumes if Success is not set then we should disconnect; however that just means Android isn't finished. This can be seen in this answer: https://stackoverflow.com/questions/72099997/android-ble-device-keep-disconnecting-after-a-succesfull-characteristic-write

[weliem]

Don't believe everything you read on Stackoverflow. In this case the article is clearly wrong. My implementation is definitely correct.

[sean7512]

Got it. I am debugging an interesting thing right now. When 2 android phones are both connected to each other (each device is a central and a peripheral) and I background and of the apps (which stops scanning/advertising and closes both the central manager and peripheral manager), onServicesDiscovered is getting triggered.

[sean7512]

I have been able to work around the issue by checking to see if the service is null or not. In the case where I am getting the erroneous callback, the service is null and I can ignore it. I was just trying to track down where it is coming from. Oddly enough, when disconnecting an iOS device I do not get the same behavior on the Android side.

[weliem]

Android seems to have issues when it is both a central and peripheral at the same time. Never been able to find a workaround for that....let me know if you find something

[sean7512]

I have been able to workaround this issue by doing a simple check at the top of onServicesDiscovered, like so...

@Override
public void onServicesDiscovered(final BluetoothPeripheral peripheral) {
    if (peripheral.getService(TARGET_SERVICE_UUID) == null) {
        return;
    }
...

Essentially when this is called as a device disconnects, calling getService (for what I am expecting) will return null and I can safely ignore. As I said, when an iOS device disconnects from Android, this callback does not occur. This "fix" is only for Android<->Android when using central/peripheral of the same service(s) at the same time.

[weliem]

Right, that may work indeed.

I still haven't found a way to deal with the issue inside the library....