Comment trouver l'emplacement de l'utilisateur en utilisant la tour de téléphonie cellulaire?

class MyLocationActivity
extends MapActivity {
MapController mapController;
MyPositionOverlay positionOverlay;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
MapView mapView = (MapView) findViewById(R.id.mapview);
mapController = mapView.getController();
//Configure the map display options
mapView.setSatellite(true);
mapView.setStreetView(true);
mapView.displayZoomControls(false);
mapController.setZoom(17);
//Add the MyPositionOverlay
positionOverlay = new MyPositionOverlay();
List<Overlay> overlays = mapView.getOverlays();
overlays.add(positionOverlay);
LocationManager locationmanager;
String context=Context.LOCATION_SERVICE;
locationmanager=(LocationManager) getSystemService(context);
String provider=LocationManager.NETWORK_PROVIDER;
Location location= locationmanager.getLastKnownLocation(provider);
updateWithNewLocation(location);
}
private void updateWithNewLocation(Location location) {
if(location!=null){
positionOverlay.setLocation(location);
Double lat=location.getLatitude()*1E6;
Double lon=location.getLongitude()*1E6;
GeoPoint point = new GeoPoint(lat.intValue(),lon.intValue());
mapController.animateTo(point);
}
else{
}
}
@Override
protected boolean isRouteDisplayed() {
//TODO Auto-generated method stub
return false;
}
}

et MyPositionOverlay est ici aussi.....

public class MyPositionOverlay extends Overlay {
private final int mRadius = 5;
Location location;
public Location getLocation() {
return location;
}
public void setLocation(Location location) {
this.location = location;
}
@Override
public void draw(Canvas canvas, MapView mapView, boolean shadow) {
Projection projection = mapView.getProjection();
if (shadow == false) {
//Get the current location
Double latitude = location.getLatitude()*1E6;
Double longitude = location.getLongitude()*1E6;
GeoPoint geoPoint;
geoPoint = new GeoPoint(latitude.intValue(),longitude.intValue());
//Convert the location to screen pixels
Point point = new Point();
projection.toPixels(geoPoint, point);
RectF oval = new RectF(point.x - mRadius, point.y - mRadius,
point.x + mRadius, point.y + mRadius);
//Setup the paint
Paint paint = new Paint();
paint.setARGB(250, 255, 0, 0);
paint.setAntiAlias(true);
paint.setFakeBoldText(true);
Paint backPaint = new Paint();
backPaint.setARGB(175, 50, 50, 50);
backPaint.setAntiAlias(true);
RectF backRect = new RectF(point.x + 2 + mRadius, point.y - 3*mRadius,
point.x + 65, point.y + mRadius);
//Draw the marker
canvas.drawOval(oval, paint);
//canvas.drawLines(pts, paint);
canvas.drawRoundRect(backRect, 5, 5, backPaint);
canvas.drawText("I am here", point.x + 2*mRadius, point.y, paint);
}
super.draw(canvas, mapView, shadow);
}
}