4 items to check if a Flex 4 Application is leaking memory !

I have been working with Flash Builder profiler for past few months. After looking at few applications and memory leaks in them I came up with following 4 items which can cause a Flex application to leak memory.

If you don't like to read lot of text the gist is to use weak references where ever possible.

1. addEventListener is being called with the default value of false for its useWeakReference flag.

2. bindProperty and bindSetter methods of BindingUtils are called with default value of false for its useWeakReference flag.

Please note: I don't know what is the equivalent thing in Flex 3.

3. ChangeWatcher.watch method is being called with default value of false for its useWeakReference flag.

Please note: I don't know what is the equivalent thing in Flex 3.

4. Dictionaries are being used with weakKeys flag in the constructor set to false.

Items 3 and 4 can cause some hidden links to be formed and memory to leak. More on that soon.

Fixing itemRenderer memory leak in AdvancedDataGrid on columns change

Please read the discussion about memory leak here.

I think I found the workaround for this issue. We need to override the set columns method in a extended ADG class and add the code to free the dictionary holding on to the itemRenderers. Here is the code.

<?xml version="1.0" encoding="utf-8"?>
<mx:AdvancedDataGrid xmlns:mx="http://www.adobe.com/2006/mxml">
 <mx:Script>
  <![CDATA[
   override public function set columns(value:Array):void
   {
    super.columns = value;
    itemRendererToFactoryMap = new Dictionary(false);
   }
  ]]>
 </mx:Script>
</mx:AdvancedDataGrid>