I am not capable of helping you as I have very little experience of Mobile testing. You may ask Mobile testing experts ( specifically @Chris_Trevarthen ) for help.
You shared just 2 lines of code fragment and wrote “it is not working”. That’s not enough. We can not see how your target application looks like. We can not see what you expected to see and what you actually saw. We need to see whole lines of your test script rather than 2 lines of code fragment. We need to see the log you got.
Please have a look at the following post and provide more information about your issue.