位置每35秒更新一次，并在当前位置绘制一个圆圈

绘制时需要记住以下几点：

1. 不要阻塞主UI线程
2. 记住回收对象。
3. 记住回收对象。
4. 并始终记住回收对象。

可能的UI线程阻塞

这段代码看起来像在回调上调用一个潜在的昂贵动作

onLocationChanged()

String address = ConvertPointToLocation(point);Toast.makeText(getbaseContext(), address, Toast.LENGTH_SHORT).show();

更好地管理地图资源

确保每次都回收实例并重置其位置，而不是每次都添加新的叠加层。

private class GPSLocationListener implements LocationListener {    MapOverlay mOverlay;    public GPSLocationListener() {    }   @Override   public void onLocationChanged(Location location) {    if (location != null) {        GeoPoint point = new GeoPoint(     (int) (location.getLatitude() * 1E6),      (int) (location.getLongitude() * 1E6));        findUsersInCurrentRadius(4,location.getLatitude(),location.getLongitude());        mapController.animateTo(point);        mapController.setZoom(15);        if (mOverlay == null) { // Add this marker to the list of overlays always. // This stuff never changes so there is no need to do this logic // Every 30 secs. Loading images is **Expensive** mOverlay = mMapOverlay = new MapOverlay(this,android.R.drawable.star_on); List<Overlay> listOfOverlays = mapView.getOverlays(); listOfOverlays.add(mMapOverlay);        }        // **See, no need to make a new Object here**        mOverlay.setPointToDraw(point);        // This can probably be done at another time.        // String address = ConvertPointToLocation(point);        // Toast.makeText(getbaseContext(), address, Toast.LENGTH_SHORT).show();        mapView.invalidate();    }

这段代码可以重用此标记，并且只需更新其位置即可。如果不在列表中，则只应创建一个。

更好的绘图

好的，接下来请记住，如果不需要，不要在onDraw（）方法中创建对象。一旦标记知道要绘制到的位置，就应该缓存所有内容，以便您可以专注于绘制。例如：

public class MapOverlay {    private GeoPoint pointToDraw;    int[] imageNames=new int[6];    // This is the cached Point on the screen that will get refilled on every draw    private Point mScreenPoints;    // This is the cached depred bitmap that will be drawn each time    private Bitmap mBitmap;    // Cached Paint    private Paint mCirclePaint;    public MapOverlay(GPSLocationListener gpsLocationListener, int currentUser) {      imageNames[0]=currentUser;      // This only needs to be made here, once. It never needs to change.      mCirclePaint = new Paint(Paint.ANTI_ALIAS_FLAG);      mCirclePaint.setColor(0x30000000);      mCirclePaint.setStyle(Style.FILL_AND_STROKE);      // We only need to load this image once and then just keep drawing it when dirtyed.      mBitmap = BitmapFactory.depreResource(context.getResources(),imageNames[0]);      // This Point object will be changed every call to toPixels(), but the instance can be recycled      mScreenPoints = new Point();    }    public void setPointToDraw(GeoPoint point) {      pointToDraw = point;    }    public GeoPoint getPointToDraw() {      return pointToDraw;    }    public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when) {      super.draw(canvas, mapView, shadow);      // In the case where nothing has been set yet, don't do any drawing      if (pointToDraw == null) {         return true;      }      //--------------draw circle----------------------      mScreenPoints = mapView.getProjection().toPixels(pointToDraw, mScreenPoints);      int totalCircle=4;      int radius=40;      int centerimagesize=35;      for (int i = 1; i <= totalCircle; i ++) {canvas.drawCircle(screenPts.x,screenPts.y, i*radius, mCirclePaint);       }      canvas.drawBitmap(mBitmap, (screenPts.x-(centerimagesize/2)),(screenPts.y-(centerimagesize/2)), null);      super.draw(canvas,mapView,shadow);      return true;    }