Hi Abhiram,
The fiori extensability concept is the beautiful and flexible feature to make use of Oops Inheritance and method overriding properties. So whenever you extend an application you will be given with full access to parent class methods and variables. So for your problem to be solved you can override handleSelect method to get hold of selected Item information. In your custom controller make sure that you have overrided this method and do your manipulations. Finally when application is running, run time will take your master controller as it is and replace with the method implementations provided in extended controller.
Regards,
Arun.