Bug? USB Manager Error

[qsrtech]

Hi, Hopefully someone can help decipher this error message:
LogCat connected to: B4A-Bridge: Hewlett-Packard Slate 21-
--------- beginning of /dev/log/main
Installing file.
PackageAdded: package:qsrtech.posprintdriver
** Activity (main) Create, isFirst = true **
** Activity (main) Resume **
** Activity (main) Pause, UserClosed = false **
** Activity (driversettings) Create, isFirst = true **
Device 0 = 1659 8963
Device 1 = 1032 12291
Device 2 = 1659 8963
Device 3 = 1060 60416
printglobals_getdeviceinfo (B4A line: 103)
AConnection = Amanager.OpenDevice(ADevice, AInterface, True)
java.lang.NullPointerException
at anywheresoftware.b4a.objects.usb.UsbManagerWrapper.OpenDevice(UsbManagerWrapper.java:122)
at qsrtech.posprintdriver.printglobals._getdeviceinfo(printglobals.java:988)
at qsrtech.posprintdriver.driversettings._loaddevices(driversettings.java:2123)
at qsrtech.posprintdriver.driversettings._activity_create(driversettings.java:446)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:169)
at qsrtech.posprintdriver.driversettings.afterFirstLayout(driversettings.java:89)
at qsrtech.posprintdriver.driversettings.access$100(driversettings.java:16)
at qsrtech.posprintdriver.driversettings$WaitForLayout.run(driversettings.java:74)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)

My AManager, ADevice and AInterface appear to have valid object references.

 

[Erel]

Assuming that your code is correct then it means that the manager failed to open the device. You can use Try / Catch to catch this error.

 

[qsrtech]

Thanks. I've tried that (t/c) but it still seems to make my service crash. Is it safe to assume that if it's failing to open it then it is because it's in use?

 

[Erel]

Try / Catch should catch this error.

It fails to open the USB device. You cannot know why it failed.