android：在我添加了另一个图标叠加后，我无法更改我所在位置的图标

Question

我使用GPS来改变我的位置，然后在地图上添加叠加以显示我的位置，直到现在如果我改变我的位置图标的位置改变，但在我添加另一个叠加以显示其他图标（标记）如果我改变了地方，我的地方的图标不能改变？！为什么??

编辑：

package com.adhamenaya.android;

import java.util.List;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Point;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.MotionEvent;

import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapActivity;
import com.google.android.maps.MapController;
import com.google.android.maps.MapView;
import com.google.android.maps.Overlay;

public class MapApp extends MapActivity {

    private MapView mapView;
    private MapController mapController;
    private LocationManager locationManager;
    private GeoPoint p;
    List<Overlay> listOfOverlays ;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        initLayout();
        initMap();
        listOfOverlays = mapView.getOverlays();        
    }

    private void initLayout(){
         mapView = (MapView) findViewById(R.id.mapview);

    }
    private void initMap(){
        mapView.setBuiltInZoomControls(true);
        mapView.setStreetView(true);
        mapController=mapView.getController();
        mapController.setZoom(10);// 1 is world view
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,0, 0, new GeoUpdateHandler());

    }      
    @Override
    protected boolean isRouteDisplayed() {
        // TODO Auto-generated method stub
        return false;
    }
    class MapOverlay extends com.google.android.maps.Overlay
    {
        private GeoPoint p;
        private int res;

        public MapOverlay(GeoPoint p,int res){
            this.p=p;
            this.res=res;
        }

    @Override
     public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when) 
     {
         super.draw(canvas, mapView, shadow);                   

         //---translate the GeoPoint to screen pixels---
         Point screenPts = new Point();
         mapView.getProjection().toPixels(p, screenPts);

         //---add the marker---
         Bitmap bmp = BitmapFactory.decodeResource(getResources(),res);            
         canvas.drawBitmap(bmp, screenPts.x, screenPts.y-20, null);         
         return true;
     }

        @Override
        public boolean onTouchEvent(MotionEvent event, MapView mapView) 
        {   
            //---when user lifts his finger---
            if (event.getAction() == 1) {                
                 GeoPoint p = mapView.getProjection().fromPixels((int) event.getX(),(int) event.getY());
                 mapController.animateTo(p);
                 MapOverlay mapOverlay = new MapOverlay(p,R.drawable.redicon);
                 listOfOverlays.add(mapOverlay);        
                 mapView.invalidate();
            }                            
            return false;
        }        
    }

    class GeoUpdateHandler implements LocationListener {

        @Override
        public void onLocationChanged(Location location) {
            int lat=(int)(location.getLatitude()*1E6);
            int lng=(int)(location.getLongitude()*1E6);         
            GeoPoint p=new GeoPoint(lat,lng);
            mapController.animateTo(p);
            MapOverlay mapOverlay = new MapOverlay(p,R.drawable.blueicon);
            listOfOverlays.add(mapOverlay);        
            mapView.invalidate();

        }

        @Override
        public void onProviderDisabled(String arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onProviderEnabled(String arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
            // TODO Auto-generated method stub

        }

}

}