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AS3: How can I fire events when a property is changed in the über class?

I have a TextField inside a Sprite and I always want the alpha of the TextField to be equal to the alpha of the sprite. How can I subscribe to changes made to Sprite? I think I need to trigger the PropertychangeEvent somehow, but I can't see the sprite supports this out of the box?

class TextWidget extends Sprite{  
  private var textfield:TextField;    
  public function TextWidget(){  
    textfield = new TextField();  
    textfield.alpha = this.alpha;  //does'n help  
    addChild(textField);  
??  
  this.addEventListener(PropertyChangeEvent.PROPERTY_CHANGE, updateAlpha);  
??  
  }
  private function updateAlpha(event:PropertychangeEvent):void{  
    textfield.alpha = this.alpha;  
  }  
}
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2 answers


One way is to derive the sprite class and override the alpha property

/**
 * ...
 * @author Andrew Rea
 */
public class CustomSprite extends Sprite
{

    public static const ALPHA_CHANGED:String = "ALPHA_CHANGED";

    public function CustomSprite() 
    {

    }

    override public function get alpha():Number { return super.alpha; }

    override public function set alpha(value:Number):void 
    {
        super.alpha = value;

        dispatchEvent(new Event(CustomSprite.ALPHA_CHANGED));
    }
}


Another way would be to just set the alpha textarea when the parent sprite's alpha setter is configured as shown above, without an event.

Andrew

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Quick fix is ​​to override the alpha setter and use the value passed for the TextField as well.



public override function set alpha(value:Number):void {
    super.alpha = value;
    textField.alpha = value;
}
+1


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