| Flex 2 Developer's Guide > Customizing the User Interface > Using Styles and Themes > Using the setStyle() and getStyle() methods > Improving performance with the setStyle() method | |||
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Run-time cascading styles are very powerful, but you should use them sparingly and in the correct context. Dynamically setting styles on an instance of an object means accessing the UIComponent's setStyle() method. The setStyle() method is one of the most resource-intensive calls in the Flex framework because the call requires notifying all the children of the newly styled object to do another style lookup. The resulting tree of children that must be notified can be quite large.
A common mistake that impacts performance is overusing or unnecessarily using the setStyle() method. In general, you only need the setStyle() method when you want to change styles on existing objects. Do not use it when setting up styles for an object for the first time. Instead, set styles in an <mx:Style> block, through an external CSS style sheet, or as global styles. It is important to initialize your objects with the correct style information, if you do not expect these styles to change while your program executes (whether it is your application, a new view in a navigator container, or a dynamically created component).
Some applications must call the setStyle() method during the application or object instantiation. If this is the case, call the setStyle() method early in the instantiation phase. Early in the instantiation phase means setting styles from the component or application's preinitialize event, instead of the creationComplete or other event. By setting the styles as early as possible during initialization, you avoid unnecessary style notification and lookup. For more information about the component startup life cycle, see Improving Startup Performance in Building and Deploying Flex 2 Applications.
Flex 2.01
