how to redirect the traffic through ZAP for mobile applications security testing using ZAP

I have followed the steps which is in this website Click here for websitefor andriod setup. Websites or URL's are displaying under Sites tree in ZAP, but when i used any application those services are not displayed under sites tree. Can't we catch the API's or URL's in mobile application using ZAP tool??? Does anything need to do from my side or anything wrong i have done??? Correct me if i am wrong!!!