Android Question how to detect in the app, if ADB is used

You can use the NotificationListener library to find out when the ADB notification appears.

Another possible solution: http://stackoverflow.com/questions/27884372/detect-if-adb-server-is-running-on-android (use Phone.Shell run those programs).

Thanks, Erel.
But result of "getprop init.svc.adbd" is always "running". It's "stopped" only when the developer debugging is disabled.
Is it correct ? I meant to detect USB connection when acces to the file system can be got.

I haven't tried it.

Reboot your device with this setting enabled and see whether it starts or not.