Help!! Infowindow has no style

[jianhuizhou]

When I use the follow code to show a popup infowindow,it has no style? Why? I use 2.3.1,but in 2.2 it's Ok.

var infoWindow:InfoWindow=new InfoWindow(map);
infoWindow.label=infoData.title || "";
var myInfoPop:MyInfoPop=new MyInfoPop();
infoWindow.content=myInfoPop;
             infoWindow.setVisible(true, false);
infoWindow.show(infoData.point);
map.addChild(infoWindow);