R – Actionscript 3: Do you need to remove EventListeners

actionscript-3

In actionscript 3, I dynamically create objects to which I add EventListeners. These objects are added to arrays and might be removed again later. And others might be added later again. Each time I create an object, I add these EventListeners to them. However, is it necessary to remove these event listeners too, when deleting these objects? What happens when I lose all references to an object but don't delete these EventListeners? Do they stay somewhere in the memory, unreachable and unusuable, or does the GC clean them up?

Best Answer

Yes, you have to remove event listeners if you are not using weak references. GC won't clean up an object if there is a reference to it, and registering event listeners do create a reference to the object unless you set the useWeakReference parameter (the 5^th parameter to the addEventListener method) to true while registering the event listener. Weak references won't be counted by the garbage collector.

//Using strong reference: needs to be removed by calling removeEventListener
sprite.addEventListener(Event.TYPE, listenerFunction, useCaptureBool, 0, false);

//Using a weak reference: no need to call removeEventListener
sprite.addEventListener(Event.TYPE, listenerFunction, useCaptureBool, 0, true);

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R – Scrollable regions in ActionScript 3 Visualization

After adding the children to each Canvas you may need to call Canvas.invalidateSize() (on each one) to get them to recalculate their sizing.

Needing to do this depends on which stage in the Component Lifecycle you're adding the children - i.e. when you're calling '_drawColumLabels'.

I presume you're wanting a scollbar to appear on _colSprite (and _rowSprite) if there are more labels in it than can be displayed in it's visible area? If this is the case you'll need to use something other than Sprite, like Canvas as Sprite doesn't support scrolling.

You may also want to debug the x/y/width/height values of each of your components to make sure they're what you expect - something I find helpful with doing layout is to draw the layout on paper and start writing sizes and coordinates so that I can see that my calculations are right.

R – Actionscript 3.0 Best Option for Subclassing Vector Class (Flash Player 10)

If adding your additional functionality doesn't require access to protected properties/methods of Vector, you could create a wrapper class for the Vector. Something along these lines?

import flash.utils.Proxy;
import flash.utils.flash_proxy;

use namespace flash_proxy;

public class NumericVector extends Proxy
{
     private var vector:Vector.<Number>;

     public function NumericVector(vector:Vector.<Number> = null)
     {
          if(vector == null)
          {
              this.vector = new Vector.<Number>();
          }
          else
          {
              this.vector = vector;
          }
     }

     override flash_proxy function nextName(index:int):String 
     {
         return vector[index - 1].toString();
     }

     override flash_proxy function nextNameIndex(index:int):int
     {
         // implementation
     }

     public function sum():Number
     {
         // do whatever you intend to do
     }

     ...
}

Best Answer

Related Solutions

R – Scrollable regions in ActionScript 3 Visualization

R – Actionscript 3.0 Best Option for Subclassing Vector Class (Flash Player 10)

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