Flex Component Lifecycle: validateNow, validateDisplayList, invalidateDisplalList, commitProperties, etc.

Question

I am extending VBox to make a Calendar component. What method should I override to add the code to draw itself? What is the difference between all these methods? Is there something I should be putting in each one, or is there a specific method I can just override, add my drawing code, and have it work?

Thanks!

Answer 1

This white-paper is perhaps the best source of information I have seen on the subject.

Answer 2

I also recommend this article:

http://maohao.wordpress.com/2009/02/02/6-steps-in-creating-custom-uicomponent-in-flex-halo-framework/

Briefly, if you're doing graphics operations to draw, you'll want to use override updateDisplayList() and call invalidateDisplayList() as necessary; if you're using subcomponents, you'll use commitProperties()/invalidateProperties(). If you're dynamically sized, you'll need measure() and invalidateSize().

Answer 3

Override updateDisplayList method of UIComponent and do your drawing in it. Use the component's unscaledWidth and unscaledHeight as the bounds for drawing.

Answer 4

Deepa's MAX 2008 talk was easily the best and most easily understanding presentation on the topic. It shows exactly how to write components properly in Flex 3.

Answer 5

From Adobe Flex 3 Live Docs Advanced Visual Components in ActionScript - great source.