location为空，无法获取地理位置

                LocationManager locManager=(LocationManager)getSystemService(Context.LocationService);                 Criteria criteria=new Criteria();                criteria.setAccuracy(Criteria.ACCURACY_FINE);                criteria.setPowerRequirement(Criteria.POWER_LOW);                criteria.setAltitudeRequired(false);                criteria.setBearingRequired(false);                criteria.setCostAllowed(false);//不需要花钱            String provider=locManager.getBestProvider(criteria, true);//addGpsStatusListener(listener);            Location location=locManager.getLastKnownLocation(provider);            locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 10, listener);

LocationManager locationManager = (LocationManager)this.getSystemService(Context.LOCATION_SERVICE);        // Define a listener that responds to locationupdates        LocationProvider provider=locationManager.getProvider(LocationManager.NETWORK_PROVIDER);        LocationListener locationListener = new LocationListener() {    public void onLocationChanged(Location location) {      // Called when a new location is found by the network           makeUseOfNewLocation(location);    }    public void onStatusChanged(String provider, int status, Bundle extras) {}    public void onProviderEnabled(String provider) {}    public void onProviderDisabled(String provider) {}  };                // Register the listener with the Location Manager to receive location updates          locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);