android getlastknownlocation 在模拟器中始终为空

Question

It seems a common issue, but i really can't understand why is it happening even though i read ton of simialr issues.

I am playing with a basic location class on a emulator device, i set everything - permissions (FINE and COARSE) , i have set the coordinates in the DDMS i also tried using the telnet and then , but no matter what it always crashes witth nullpointer exception on the line with getlastknownlocation, any ideas whats wrong here ?

public class MainActivity extends Activity implements LocationListener {



private static LocationManager ok;
private Location L;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);



    ok=(LocationManager)this.getSystemService(ok.GPS_PROVIDER);
    L=ok.getLastKnownLocation(ok.GPS_PROVIDER);












}

@Override
public void onLocationChanged(Location Loc) {


    try {


        double latop=Loc.getLatitude();
        double longe=Loc.getLongitude();

        Log.i("OK", "and"+longe+""+latop);


    } catch (NullPointerException e)

    {

    }




}

Answer 1

getLastKnownLocation() will return null in general, if no app has requested a location fix from your desired provider recently.

On the emulator, it seems to take it one step further: you do not get a location unless one has been delivered to the emulator since your app has called requestLocationUpdates() .

The general pattern for using getLastKnownLocation() , if you want decent odds of getting an actual Location , is to use requestLocationUpdates() and removeLocationUpdates() to ensure that LocationManager is actively seeking locations via your chosen provider. Of course, you could also use LocationListener and onLocationChanged() , rather than getLastKnownLocation() , if you so chose.

Answer 2

@CommonsWare's answer is clear. To get not-null on emulator go to Google Maps application and after that you get some location

Answer 3

There is another option, to create your own provider using locationManager.addTestProvider(); so you can make your own tests.