Question

If I have a button on the timeline for the first few frames, but then I remove it…

Do I have to worry about removing the event listener for the button (MovieClip) if the button has be removed from the stage?

I’m writing a Document Class even though I’m using objects on the timeline.

Answer 1

You could use the removedFromStage event to clear up any event listeners on your button instance:

package 
{
    import flash.display.MovieClip;
    import flash.events.Event;
    import flash.events.MouseEvent;

    public class Button extends MovieClip
    {
        public function Button():void
        {
            addListeners();
        }

        private function addListeners():void
        {
            this.addEventListener(Event.ADDED_TO_STAGE, addedHandler);
            this.addEventListener(Event.REMOVED_FROM_STAGE, removedHandler);
            this.addEventListener(MouseEvent.CLICK, clickHandler);
        }

        private function addedHandler(event:Event):void
        {
            trace("button added");
        }

        private function removedHandler(event:Event):void
        {
            trace("button removed");
            removeListeners();
        }

        private function clickHandler(event:MouseEvent):void
        {
            trace("button clicked");
        }

        private function removeListeners():void
        {
            this.removeEventListener(Event.ADDED_TO_STAGE, addedHandler);
            this.removeEventListener(Event.REMOVED_FROM_STAGE, removedHandler);
            this.removeEventListener(MouseEvent.CLICK, clickHandler);

            trace("has added listener: " + this.hasEventListener(Event.ADDED_TO_STAGE)); 
            trace("has removed listener: " + this.hasEventListener(Event.REMOVED_FROM_STAGE));
            trace("has click listener: " + this.hasEventListener(MouseEvent.CLICK));
        }
    }
}