Question

<?xml version="1.0" encoding="utf-8"?>
<s:HGroup xmlns:fx="http://ns.adobe.com/mxml/2009" 
          xmlns:s="library://ns.adobe.com/flex/spark" 
          xmlns:mx="library://ns.adobe.com/flex/mx" width="400" height="300">
    <fx:Script>
        <![CDATA[
            import mx.events.FlexEvent;

            override protected function updateDisplayList( unscaledWidth : Number, unscaledHeight : Number ) : void
            {
                super.updateDisplayList( unscaledWidth, unscaledHeight );
            }

        ]]>
    </fx:Script>
    <fx:Declarations>
        <!-- Place non-visual elements (e.g., services, value objects) here -->
    </fx:Declarations>
</s:HGroup>

• super.updateDisplayList( unscaledWidth, unscaledHeight );

• why throwing “Call to possible undefined function updateDisplayList” ?

Answer 1

In Spark, the “s:HGroup” is no longer a DisplayObject like “HBox”. Can be used just for layout and groupping. So no background color or something else can updated on HGroup.

In consequence it does not have the updateDisplayList() method inside.

I suggest to wrap your component inside a SkinableContainer and use the following “workaround” (in case you still want to stay with spark)

<?xml version="1.0" encoding="utf-8"?>
<s:SkinnableContainer
          xmlns:fx="http://ns.adobe.com/mxml/2009" 
          xmlns:s="library://ns.adobe.com/flex/spark" 
          xmlns:mx="library://ns.adobe.com/flex/mx" width="400" height="300">
<s:HGroup width="100%" height="100%" >
    <fx:Script>
        <![CDATA[
            import mx.events.FlexEvent;

            override protected function updateDisplayList( unscaledWidth : Number, unscaledHeight : Number ) : void
            {
                super.updateDisplayList( unscaledWidth, unscaledHeight );
            }

        ]]>
    </fx:Script>
    <fx:Declarations>
        <!-- Place non-visual elements (e.g., services, value objects) here -->
    </fx:Declarations>
</s:HGroup>
</s:SkinnableContainer>