Macromedia flex 2 Manuel

Writing an effect for a transition

243

5.

Flex applies the destination view state to the application.

6.

Flex dispatches the 

currentStateChange

 event.

7.

Flex plays the effects defined in the transition. 

As part of playing the effect, Flex invokes the factory class 

play()

 method, 

Effect.play()

, to initialize 

propertyChanges.end

 for effect instances. 

Example: Creating a transition effect

This section modifies the Rotation effect created in 

 to make the effect usable in a transition. 

The following example shows the RotationTrans.as class that definesthe factory class for the 
effect. The only modification you make to Rotation.as to create RotationTrans.as is to remove 
the default value definitions for the 

angleFrom

 and 

angleTo

 property definitions. The 

RotationTransInstance.play()

 method determines the default values. 

package myEffects
{
    // myEffects/RotationTrans.as
    import mx.effects.TweenEffect;
    import mx.effects.EffectInstance;
    import mx.effects.IEffectInstance;

    public class RotationTrans extends TweenEffect
    {
        // Define parameters for the effect.
        // Do not specify any default values. 
        // The default value of these properties is NaN.
        public var angleFrom:Number;
        public var angleTo:Number;
  
        // Define constructor with optional argument.
        public function RotationTrans(targetObj:Object = null) {
            super(targetObj);
            instanceClass= RotationTransInstance;           
        }

        // Override getAffectedProperties() method to return "rotation".
        override public function getAffectedProperties():Array {
            return ["rotation"];
        }
    
        // Override initInstance() method.
        override protected function initInstance(inst:IEffectInstance):void 
{
            super.initInstance(inst);
            RotationTransInstance(inst).angleFrom = angleFrom;