Why does the program not call the method "onLocationChanged"? - android-studio

Question

i wrote this simple code for getting the GPS coordinates but it doesnt call the method "onChangedLocation". I know it should jump into the method only when the coordinates change, but at first start it always should jump into that method or not?
It should display the longtitude and latitude in the catlog.
Im using my phone for debugging.
package tabs;
import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import androfenix.whetoo.R;
public class Tab1 extends ListFragment implements LocationListener {
double latitude;
double longitude;
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.tab_local, container, false);
String[] abc = {"Message1", "Message2", "Message3", "Message1", "Message2", "Message3", "Message1", "Message2", "Message3", "Message1", "Message2", "Message3"};
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),
android.R.layout.simple_list_item_1, abc);
setListAdapter(adapter);
LocationManager locationManager = (LocationManager) getActivity().getSystemService(Context.LOCATION_SERVICE);
if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED &&
ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
}
return v;
}
#Override
public void onLocationChanged(Location location) {
Log.d("onLocationChanged", "onLocationChanged wird aufgerufen");
longitude = location.getLongitude();
String name = String.valueOf(longitude);
Log.d("longtitude", name);
latitude = location.getLatitude();
String name2 = String.valueOf(latitude);
Log.d("latitude", name2);
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
#Override
public void onProviderEnabled(String provider) {
}
#Override
public void onProviderDisabled(String provider) {
}
}