Ans:

Using Implement IInvalidating interface or extend UIComponent.

for example:

public class BadList extends VBox
{
private var _dataprovider : ArrayCollection
public function set dataprovider( arr: ArrayCollection ):void{
this._dataprovider = arr;
arr.addEventListner( CollectionEvent COLLECTION_CHANGE,
 dataProviderChangeHandler);
}
private function dataProviderChangeHandler(e:Event):void{
this.removeAllChildren();
for each(var n:Number in this._dataProvider){
var l:Label = new Label();
l.text = n.toString();
this.addChild(l);
}
}
public function BadList(){
}
}