About Creating Components - MACROMEDIA FLEX-CREATING ADVANCED COMPONENTS Manual

This article describes the details of creating advanced components for use in Macromedia Flex
applications. The majority of the work is in writing the ActionScript class file, which derives from
Flex existing classes, and adding your own custom functionality.
For an additional article on creating Flex components, including examples, see
www.macromedia.com/devnet/flex/articles/creating_comp.html.
About creating components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Writing the component's ActionScript code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Compiling components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Making components accessible. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Adding versioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Best practices when designing a component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Using the ModalText example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

About creating components

Most new controls extend an existing class. If you want to create a component that is based on the
Button control, for example, you can subclass the mx.controls.Button class. However, if you want
to invent your own component, you will likely extend either the mx.core.UIComponent or
mx.core.UIObject class. Choosing one of these base classes is discussed later, but Macromedia
recommends that most custom components extend the UIComponent class rather than the
UIObject class.
Use the following general process for creating a new Flex component in Flash:
If necessary, create symbols for skins or icons in Flash.
1
Create an ActionScript class file.
2
Extend one of the base classes (UIObject or UIComponent) or another component.
a
Specify properties that the user can set using an MXML tag property.
b
Embed graphics and skins.
c
Implement the
d
Creating Advanced Components
method.
init()
5