Macromedia flex 2 Manual

232

Creating Effects

Example: Defining a simple effect

To define a simple custom effect, you create a factory class from the 

Effect

 base class, and the 

instance class from the mx.effects.EffectInstance class. The following example shows an effect 
class that uses a 

Sound

 object to play an embedded MP3 file when a user action occurs. This 

example is a simplified version of the 

SoundEffect

 class that ships with Flex.

package myEffects
{
    // myEffects/MySound.as
    import mx.effects.Effect;
    import mx.effects.EffectInstance;
    import mx.effects.IEffectInstance;

    public class MySound extends Effect
    {
        // Define constructor with optional argument.
        public function MySound(targetObj:Object = null) {
            // Call base class constructor.
            super(targetObj);
            
            // Set instanceClass to the name of the effect instance class.
            instanceClass= MySoundInstance;         
        }
      
        // This effect modifies no properties, so your 
        // override of getAffectedProperties() method 
        // returns an empty array.
        override public function getAffectedProperties():Array {
            return [];
        }
        
        // Override initInstance() method.
        override protected function initInstance(inst:IEffectInstance):void 
{
            super.initInstance(inst);
        }   
    }
}

The 

package

 statement in your class specifies that you should deploy it in a directory called 

myEffects. In this example, you place it in the subdirectory of the directory that contains your 
Flex application. Therefore, the namespace definition in your Flex application is 

xmlns:MyComp="myEffects.*"

. For more information on deployment, see 

.