resource ID R.id.map is added automatically to the Android project when you build the layout file

resource ID R.id.map is added automatically to the Android project when
you build the layout file

Hi i am working on map application in which resource ID R.id.map should
added automatically to the Android project when you build the layout file.
but it giving error and not resolving it automatically. how to resolve it.
thanks
mMap = ((MapFragment)
getFragmentManager().findFragmentById(R.id.map)).getMap();