I had the same problem. It seems you can get the center this way:
mMap.getCameraPosition().target
where mMap is the GoogleMap instance from your activity. This will return a LatLng object which basically represents the center of the map.
Note that the GeoPoint
class is not available anymore.
According to http://developer.android.com/reference/com/google/android/gms/maps/model/CameraPosition.html
target is “The location that the camera is pointing at.” (I tested it with the sample code and it worked okay for me)