SpriteをUIに追加

UIComponentを通じて追加しましょう。

var mySprite:Sprite = new Sprite();
mySprite.graphics.beginFill(0xFFCC00);
mySprite.graphics.drawCircle( 40, 40, 40 );
var UIRef:UIComponent = new UIComponent();
addChild(UIRef);
UIRef.addChild(mySprite);

Adding a Sprite Object using the Flex addChild() method
http://casario.blogs.com/mmworld/2008/01/adding-a-sprite.html