Определение местоположения пользователя на картах osm

Я работаю над приложением для Android, которое определяет местоположение пользователя в картах osm. Я могу показать местоположение пользователя на карте, но если местоположение меняется, вся карта перезагружается, что с этим не так? Кроме того, как я могу повысить точность определения местоположения пользователя? И как я могу сделать круг, который увеличивается и уменьшается в соответствии с точностью (как показано в Google)?

код:

public class OsmDemoActivity extends Activity implements LocationListener, 
    MapViewConstants 
{  
private MapView mMapView; 
private MapController mapController; 
private LocationManager mLocMgr; 
private ItemizedOverlay<OverlayItem> mMyLocationOverlay; 
private ResourceProxy mResourceProxy; 

ArrayList<OverlayItem> items;

@Override 
public void onCreate(Bundle savedInstanceState) 
{ 
    super.onCreate(savedInstanceState); 
    mResourceProxy = new DefaultResourceProxyImpl(getApplicationContext()); 
    setContentView(R.layout.main); 
    //mMapView.setUseDataConnection(false);
    initilaizeMap();
    //addOverlay(); 
    mLocMgr = (LocationManager) getSystemService(LOCATION_SERVICE); 
    mLocMgr.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);      
} 

public void initilaizeMap()
{
    mMapView = (MapView) this.findViewById(R.id.mapView); 
    mMapView.setTileSource(TileSourceFactory.MAPNIK); 



    //mMapView.setUseDataConnection(false);



    mMapView.setBuiltInZoomControls(true); 
    mMapView.setMultiTouchControls(true); 
    mapController = this.mMapView.getController(); 
    mapController.setZoom(15); 
    mapController.setCenter(new GeoPoint(15.610762,32.540345));


    /*
    final MyLocationOverlay myLocationOverlay = new MyLocationOverlay(this, mMapView, 
            mResourceProxy); 
    myLocationOverlay.enableMyLocation();
    //myLocationOverlay.disableMyLocation(); // not on by default 
    myLocationOverlay.disableCompass(); 
    myLocationOverlay.disableFollowLocation(); 
    myLocationOverlay.setDrawAccuracyEnabled(true); 
    myLocationOverlay.runOnFirstFix(new Runnable() { 
        public void run() { 
            mapController.animateTo(myLocationOverlay 
                    .getMyLocation()); 
        } 
    }); 
    //ArrayList<OverlayItem> mOsmOverlays;
    //mOsmOverlays.add(myLocationOverlay); 
    */
}

public void addOverlay()
{
    GeoPoint point2 = new GeoPoint(53554070, -2959520); // centre map here 
    GeoPoint point3 = new GeoPoint(53554070 + 1000, -2959520 + 1000); // icon goes here 
    GeoPoint point4 = new GeoPoint(15.610844, 32.540045);
    GeoPoint point5 = new GeoPoint(15610844 + 40, 32540045 + 40);
    GeoPoint point6 = new GeoPoint(15610844 + 50, 32540045 + 50);
    GeoPoint point7 = new GeoPoint(15610844 + 10, 32540045 +10);
    mapController.setCenter(point4);
    items = new ArrayList<OverlayItem>(); 
    // Put overlay icon a little way from map center 
    items.add(new OverlayItem("Here5", "SampleDescription", point5)); 
    items.add(new OverlayItem("Here6", "SampleDescription", point6));
    items.add(new OverlayItem("Here7", "SampleDescription", point7));
    /* OnTapListener for the Markers, shows a simple Toast. */ 
    this.mMyLocationOverlay = new ItemizedIconOverlay<OverlayItem>(items, 
            new ItemizedIconOverlay.OnItemGestureListener<OverlayItem>() { 
                @Override 
                public boolean onItemSingleTapUp(final int index, 
                        final OverlayItem item) { 
                    Toast.makeText( 
                            OsmDemoActivity.this, 
                            "Item onItemSingleTapUp '" + item.mTitle, Toast.LENGTH_LONG).show(); 
                    return true; // We 'handled' this event. 
                } 
                @Override 
                public boolean onItemLongPress(final int index, 
                        final OverlayItem item) { 
                    Toast.makeText( 
                            OsmDemoActivity.this,  
                            "Item onItemLongPress '" + item.mTitle ,Toast.LENGTH_LONG).show(); 
                    return false; 
                } 
            }, mResourceProxy); 
    this.mMapView.getOverlays().add(this.mMyLocationOverlay); 
    mMapView.invalidate(); 
}

public void displayLocation(GeoPoint loc)
{
    mapController.setCenter(loc);
    items = new ArrayList<OverlayItem>(); 
    // Put overlay icon a little way from map center
    items.add(new OverlayItem("Here u r", "SampleDescription", loc));
    /* OnTapListener for the Markers, shows a simple Toast. */ 
    this.mMyLocationOverlay = new ItemizedIconOverlay<OverlayItem>(items, 
            new ItemizedIconOverlay.OnItemGestureListener<OverlayItem>() { 
                @Override 
                public boolean onItemSingleTapUp(final int index, 
                        final OverlayItem item) { 
                    Toast.makeText( 
                            OsmDemoActivity.this, 
                            "Item onItemSingleTapUp '" + item.mTitle, Toast.LENGTH_LONG).show(); 
                    return true; // We 'handled' this event. 
                } 
                @Override 
                public boolean onItemLongPress(final int index, 
                        final OverlayItem item) { 
                    Toast.makeText( 
                            OsmDemoActivity.this,  
                            "Item onItemLongPress '" + item.mTitle ,Toast.LENGTH_LONG).show(); 
                    return false; 
                } 
            }, mResourceProxy); 
    mMapView.getOverlays().clear();
    this.mMapView.getOverlays().add(this.mMyLocationOverlay); 
    //mMapView.invalidate();
}

public void onLocationChanged(Location location)
{ 
    int lat = (int) (location.getLatitude() * 1E6); 
    int lng = (int) (location.getLongitude() * 1E6); 
    GeoPoint gpt = new GeoPoint(lat, lng); 
    //mapController.setCenter(gpt); 
    //mMapView.invalidate();
    displayLocation(gpt);
} 

    @Override 
    public void onProviderDisabled(String arg0) {} 
    @Override 
    public void onProviderEnabled(String provider) {} 
    @Override 
    public void onStatusChanged(String provider, int status, Bundle extras) {} 

}