局部ALERT效果

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
    <mx:Script>
        <!--[CDATA[
            import mx.containers.TitleWindow;
            import mx.managers.PopUpManager;
            function onclick(e:MouseEvent) {
                var t = new TitleWindow();
                t.width = 200;
                t.height = 100;
                PopUpManager.addPopUp(t,e.currentTarget.parent,true);
                PopUpManager.centerPopUp(t);
                
                changeModalWindow(tn);
            }
            
            private function changeModalWindow(obj : DisplayObject) : void {
                var mw : DisplayObject = systemManager.getChildByName("modalWindow");
                mw.x = obj.x;
                mw.y = obj.y;
                mw.width = obj.width;
                mw.height = obj.height;
            }
        ]]-->
    </mx:Script>
    <mx:TabNavigator id="tn" x="133" y="78" width="363" height="325">
        <mx:Canvas label="A" width="100%" height="100%">
            <mx:Button x="51" y="35" label="Button" click="onclick(event)"/>
        </mx:Canvas>
        <mx:Canvas label="B" width="100%" height="100%">
        </mx:Canvas>
        <mx:Canvas label="C" width="100%" height="100%">
        </mx:Canvas>
    </mx:TabNavigator>
    <mx:Tree x="0" y="78" width="125" height="325"></mx:Tree>
    <mx:Canvas x="0" y="0" width="496" height="70" backgroundColor="#FFFFFF">
    </mx:Canvas>
</mx:Application>

 

技巧就是：

systemManager.getChildByName("modalWindow");

在当前systemManager里取得这个遮罩实例，名称是定死的。

然后改大小和位置就可以了