What does UIComponent add to DisplayObject?

Question

I am trying to understand the interaction between Flex UIComponents and (Flash?) DisplayObjects... But it's not clear to me what the UIComponent class "adds" to DisplayObject. So, what can a UIComponent do that a DisplayObject cannot?

Answer 1

If you look at the documentation, you can see that UIComponent adds most of the user interface functionality. DisplayObject does not respond to any user interface events. CSS style functionality is also included in UIComponents.

UIComponent -> FlexSprite -> Sprite -> DisplayObjectContainer -> InteractiveObject -> DisplayObject. Each layer adds methods and events to DisplayObject.

Answer 2

There are a lot of differences, and I would definitely go to the doc's for more detail, but here are some:
Expanded event model (when alpha, visible, width, height, scalex, scaley, x or y are changed, an event is dispatched, there is also the preinitialize, initialize, )
Additional properties (you can get the mouseX and Y relative to the children, you have access to the tweening properties array, there is a cursorManager, systemManager and a focusManager which work with the greater Flex framework and more. There is also a generic (uncast) reference to the parent and the application meaning easier access to root).
It has CSS support
Additional Methods... there are a lot.

FYI:

FlexSprite's only real difference is that overwrites toString() to provide more detail about where the object is in the hierarchy.

I would say that the best way to summarize is that the Flex UIComponent is simply more robust and significantly stronger than the DisplayObjectContainer.