Android GPS and wifi Status In application

I have implemented Android GPS application and cell-id application for location tracing separately, now I want to combine t开发者_如何学Gohe functionality of both the applications, I want to trace the location via GPS if wifi not available or vice verca. Kindly guide me how can I get the status of GPS and wifi.

http://developer.android.com/guide/topics/location/obtaining-user-location.html