As you mentioned in your question, you can check if the provider is enabled using the Location Manager isProviderEnabled method, as shown below.
LocationManager lm = (LocationManager) getActivity().getSystemService(Context.LOCATION_SERVICE);
lm.isProviderEnabled(LocationManager.GPS_PROVIDER);
FusedLocationApi GoogleApiClient LocationRequest, LocationListener, . onLocationChanged(Location location). , , onLocationChanged.
, ; , , , GoogleApiClient, , GooglePlayServices .., .