Re-starting a discovery causes a crash

[sproctor]

java.lang.IllegalStateException: Discovery is already in progress - did you call discoverDevices() multiple times?

onCompletion is never called from the demo.

Actually the stop button in the demo is enabled at the wrong time, but fixing that, hitting stop causes a hang, fixing that, causes a crash when it's restarted.

[ivanempire]

Thanks for filing this one - will be taking a look this week!