Любой способ отложить getLatKnownLocation? Android GPS

Итак, я использую метод getLastKnownLocation, чтобы получить локатор местоположения устройства, но он возвращает значение null, если нет исправления GPS. Есть ли способ отложить выполнение getLastKnownLocation, пока у GPS не будет допустимого местоположения?

package test.example;

import android.app.Activity;
import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

public class testGPS extends Activity 
{
    private LocationManager lm;
    private LocationListener locationListener;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        TextView tv = new TextView(this);


        //---use the LocationManager class to obtain GPS locations---
        lm = (LocationManager) 
            getSystemService(Context.LOCATION_SERVICE);    

        locationListener = new MyLocationListener();

        lm.requestLocationUpdates(
            LocationManager.GPS_PROVIDER, 
            0, 
            0, 
            locationListener);    

        Location loc = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

        if (loc != null) {
            tv.setText("Hello, lat is " + loc.getLatitude() + " lon is " + loc.getLongitude());
            setContentView(tv);
        } else {
            tv.setText("Hello, loc is null :(");
            setContentView(tv);
        }
    }

    private class MyLocationListener implements LocationListener 
    {
       @Override
        public void onLocationChanged(Location loc) {

        }

        @Override
        public void onProviderDisabled(String provider) {
            // TODO Auto-generated method stub
        }

        @Override
        public void onProviderEnabled(String provider) {
            // TODO Auto-generated method stub
        }

        @Override
        public void onStatusChanged(String provider, int status, 
            Bundle extras) {
            // TODO Auto-generated method stub
        }
    }        

}