(flex4): addChild() is not available in this class.

flex4中：

just create another container wich u place displayObject in:

// container ( IVisualElement ) for DisplayObjects
var container:UIComponent = new UIComponent();
addElement( container );

// displayObject goes to container
var displayO:Sprite = new Sprite();
container.addChild( displayO );

?

flex3中：

var container:UIComponent = new UIComponent();addChild( container );