android覆盖不可见

我正在制作一个基于位置的应用程序
我有以下代码：

Drawable blueDrawable = getApplicationContext().getResources().getDrawable(R.drawable.blue);
Drawable redDrawable = getApplicationContext().getResources().getDrawable(R.drawable.red);
CustomizedOverlay blueItemizedOverlay = new CustomizedOverlay(blueDrawable);
CustomizedOverlay redItemizedOverlay = new CustomizedOverlay(redDrawable);

String [] s = startloc.getText().toString().split(" ");
Log.e(tag, s[0]); Log.e(tag, s[1]);  
Double lat = Double.parseDouble(s[0]);
Double lon = Double.parseDouble(s[1]);
GeoPoint startpoint = new GeoPoint((int) (lat * 1e6) , (int) (lon * 1e6));

s = startloc.getText().toString().split(" ");
lat = Double.parseDouble(s[0]);
lon = Double.parseDouble(s[1]);
GeoPoint stoppoint = new GeoPoint((int) (lat * 1e6) , (int) (lon * 1e6));

OverlayItem overlayitem = new OverlayItem(startpoint, "base camp","");
blueItemizedOverlay.addOverlay(overlayitem);

贴图正在动画化到正确的点。但是覆盖层没有显示出来
如果您想要定制Overlay类，我会发布它
多谢各位

我忘了添加

List<Overlay> mapOverlays = mapView.getOverlays();
mapOverlays.add(blueItemizedOverlay);

List mapOverlays=mapView.getOverlays（）；
添加（blueItemizedOverlay）；