User Guide

Writing the component’s ActionScript code 7
Note: Macromedia recommends that you base your components on the UIComponent class rather
than the UIObject class. The UIComponent class provides more built-in functionality, but maintains
the flexibility of extending the UIObject class.
UIObject and UIComponent are the base classes of the component architecture. Understanding
the principles at work in these two classes is important for building components.
The following table briefly describes the two base classes:
About the UIObject and UIComponent classes
Components based on version 2 of the Macromedia Component Architecture descend from the
UIObject class, which wraps the MovieClip class. The MovieClip class is the base class for the
classes in Flash that can draw on the screen. By providing a wrapper around its methods and
properties, Flex makes the UIObject syntax more intuitive and improves the conceptual
management of representing graphic objects.
The UIObject (mx.core.UIObject) class hides the mouse handling and frame handling in the
MovieClip class. The UIObject class also defines the styles, skins, and event aspects of the
component architecture. The UIObject class and its subclasses broadcast their events just before
drawing. If you are familiar with Flash, this event is analogous to the
enterFrame() MovieClip
event. The UIObject class posts events to its listeners just before drawing when loading and
unloading, and when its layout changes (
move, resize).
A UIObject class or UIObject subclass resizes itself by scaling. When you change its size using the
setSize() method, the new dimensions are passed to the _width and _height properties of the
MovieClip class, which scale the subclass.
Class Extends Description
mx.core.UIComponent
UIObject UIComponent is the base class for all Flex components. It can
participate in tabbing, accept low-level events such as keyboard
and mouse input, and be disabled so it does not receive mouse
and keyboard input.
The UIComponent class lets you perform the following tasks:
• Create focus navigation
• Enable and disable components
• Resize components
Macromedia recommends using the UIComponent class rather
than the UIObject class as the base class for your custom
components.
mx.core.UIObject
MovieClip UIObject is the base class for all graphical objects. It can have
shape, draw itself, and be invisible.
The UIObject class lets you perform the following tasks:
• Edit styles
• Handle events
• Resize by scaling
Macromedia does not recommend using the UIObject class
rather than the UIComponent class as the base class for your
custom components.