Para comprobar la ubicación del servicio de habilitar o no en un dispositivo android

Puede comprobar si el GPS está activado o no y mostrar un mensaje si no está habilitado

        LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        if (locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {

            //here do what you want when the GPS service is enabled

            Toast.makeText(MainActivity.this, "is enable", Toast.LENGTH_SHORT).show();

        } else {

            MaterialAlertDialogBuilder locationDialog = new MaterialAlertDialogBuilder(MainActivity.this);
            locationDialog.setTitle("Attention");
            locationDialog.setMessage("Location settings must be enabled from the settings to use the application");
            locationDialog.setCancelable(false);
            locationDialog.setPositiveButton("Open settings", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                    startActivity(intent);
                }
            });
            locationDialog.create().show();
        }

    }
}