Macromedia flex 2 Manual

About creating a custom effect

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<!-- Define factory class. -->
<mx:WipeDown id="myWD" duration="1000"/>
<!-- Assign factory class to effect targets. -->
<mx:Button id="myButton" mouseDownEffect="{myWD}"/>
<mx:Button id="myOtherButton" mouseDownEffect="{myWD}"/>

By convention, the name of a factory class is the name of the effect, such as Zoom or Fade. 

Instance class

The instance class implements the effect logic. When an effect trigger 

occurs, or when you call the 

play()

 method to invoke an effect, the factory class creates an 

object of the instance class to perform the effect on the target. When the effect ends, Flex 
destroys the instance object. If the effect has multiple target components, the factory class 
creates multiple instance objects, one per target.

By convention, the name of an instance class is the name of the effect with the suffix Instance, 
such as ZoomInstance or FadeInstance.

About the effect base classes 

You define effects by creating a subclass from the effects class hierarchy. Typically, you create a 
subclass from one of the following classes:

■

mx.effects.Effect

Create a subclass from this class for simple effects that do not require 

an effect to play over a period of time. For example, the Pause effect inserts a delay 
between two consecutive effects. You can also define a simple sound effect that plays an 
MP3 file.

■

mx.effects.TweenEffect

Create a subclass from this class to define an effect that plays 

over a period of time, such as an animation. For example, the Resize effect is a subclass of 
the TweenEffect class that modifies the size of its target over a specified duration. 

About implementing your effects classes

You must override several methods and properties in your custom effect classes, and define 
any new properties and methods that are required to implement the effect. You can optionally 
override additional properties and methods based on the type of effect that you create.