I have modified my test classes slightly. And found that when debugging this
movie in Flex Builder 3, the garbage collection was triggered when I moved
my mouse within the Flash movie.
I suspect that the method behind the screens that runs the garbage collector
is quite complex. I think that in more complex applications garbage
collection is more efficient.
Counter.as
package
{
import flash.display.BitmapData;
public class Counter
{
public var bmd:BitmapData;
public function Counter()
{
bmd = new BitmapData(500, 500);
bmd.noise(Math.random() * 1000000);
};
};
};
SpriteClass.as
package
{
import flash.display.Sprite;
public class SpriteClass extends Sprite
{
public function SpriteClass()
{
};
};
};
testAS.as
package
{
import flash.display.Sprite;
import flash.events.Event;
import flash.text.TextField;
[SWF(frameRate="4")]
public class testAS extends Sprite
{
private var _t:TextField;
private var _c:uint;
private var _a:Array;
public function testAS()
{
_a = new Array();
_t = new TextField();
addChild(_t);
var a:SpriteClass = new SpriteClass();
a.addEventListener(Event.ENTER_FRAME, _handler);
};
private function _handler(e:Event):void
{
_t.text = _c.toString();
_a.push(new Counter());
_c++;
if (_c > 300)
{
(e.currentTarget as SpriteClass).removeEventListener(
Event.ENTER_FRAME, _handler);
};
};
};
};
Greetz Erik
On 3/14/08, EECOLOR <[EMAIL PROTECTED]> wrote:
>
> Hey there,
>
> I was totally shocked this morning. If what you were saying was true it
> would mean that if you created a class with a listener to itself and
> instantiated it, it would never be garbage collected.
>
> So I did some extra tests.
>
> 1. Your example with a weak listener (same result)
> 2. Trying to force garbage collection using System.gc and the
> localconnection 'hack' (same result)
>
> So I turned to the Flex
> Profiler. I used the following class to test things:
>
> package
> {
> import flash.display.Sprite;
> import flash.events.Event;
> import flash.system.System;
> import flash.text.TextField;
>
> [SWF(frameRate="1")]
> public class testAS extends Sprite
> {
> private var _t:TextField;
> private var _c:uint;
> private var _a:Array;
>
> public function testAS()
> {
> _a = new Array();
>
> _t = new TextField();
> addChild(_t);
>
> var a:SpriteClass = new SpriteClass();
> a.addEventListener(Event.ENTER_FRAME, _handler);
> };
>
> private function _handler(e:Event):void
> {
> _t.text = (_c++).toString();
> _a.push(new Counter());
> };
> };
> };
>
> Initialy the profiler showed the behaviour you were describing. However,
> if I pressed
> the "Run Garbage Collector" button, the instance of SpriteClass was removed.
> This indicates the behaviour that I described in my example.
>
>
> I changed the above example to use a weak listener. The instance of
> SpriteClass was only removed after I clicked the "Run garbage collector"
> button.
>
> In the handler I removed the listener to the SpriteClass instance. The
> instance of SpriteClass was only removed from memory after I clicked
> the "Run garbage collector" button.
>
> If I run the profiler with the
> option "Generate object allocation stack traces", the instance is removed
> everytime quite fast.
>
>
> The conclusion of all this is that my statement in previous emails was
> correct. What your example shows is that while the instance _can_ be garbage
> collected, you will never know when it actually will.
>
>
> A summary:
>
> - There is no such thing as "a reference to be created invisibly within
> the event system".
> - You can not be sure when an instance is garbage collected.
> - Weak references only indicate that: if the reference on the dispatcher
> object to the listener is the last one, the instance containing the listener
> will me available for garbage collection.
>
>
> I want to thank you Cory for being as persistent as I can be. It enabled
> me to do extensive tests to see
> how the player works. In my tests in a standalone player there were cases
> where I let the example application run for more then half an hour without
> garbage collection of SpriteClass. I am not sure when the garbage collector
> kicks in (might be triggered by total memory usage). I will continue to
> monitor the
> example
> to see if the instance will ever be garbage collected. If not, I will file a
> bug at adobe.
>
>
>
> Greetz Erik
>
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