contentPane

The Container class implements much of the behavior of the containers in the Flex Framework. This article is broken into sections to deal with each of the pieces of functionality individually.

Problem

You have a PopUpButton that is failing with a null error unexpectedly.

Solution

Reinitialize the popUp property of the PopUpButton every time it receives the addedToStage event. You can save a reference to the class in your parent component.

The contentPane property of the Container class allows Container to turn its children into grandchildren and therefore allow them to render separately from other children (such as scrollbars) which may need to live alongside them.