check if GPS is enabled

isGpsEnabled

    /**
     * Returns the current enabled/disabled status of the GPS provider.
     * <p/>
     * If the user has enabled GPS in the Settings menu, true
     * is returned otherwise false is returned
     */
    public static boolean isGpsEnabled(final Context context) {
        final LocationManager locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
        return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
    }