How do i know various activities (processes) that an app or the system has? Like what activity is triggered to take a screen shot or to open an app?

I want to write a script to automate a procedure that is, open a app and take its screenshot and then after taking screen shot close it. I want this to happen like twice a day. Is there any app in market that lets me know what all activities or processes are triggered or can be triggered or started? Or is there some other way to know the same?