Flex: AdvancedDataGrid - Memory Leak

There is known memory leak issue with AdvancedDataGrid. It happens, when we have instance of AdvancedDataGrid loaded with some data and want to update it with newly received data and recreating columns in it. Found workaround is next - create new class, which extends and use it in your code. Add next method to it:

public function clearRenderers():void {
   this.itemRendererToFactoryMap = new Dictionary(false);
   this.visibleData = new Object();
   this.listData = null;
}

Call clearRenderers() method before setting new columns. It will fix memory leak completely.

Flex: Scrolling issue with VBox content

Recently I've faced with strange issue for apps developed in Flex 3.3. I had VBox container, which is populated with new components after clicking on corresponding "Add Item" button. This VBox has fixed size and disabled horizontal scrolling:

mx:VBox height="440" width="900" verticalScrollPolicy="auto" horizontalScrollPolicy="off" ...

Issue was next - when user has added a lot of items, vertical scroll bar appears and after scrolling top and down for few times UI garbage is shown instead of properly rendered items that were added. I mean that all those items were only partially visible and messed up with each other.

Setting cacheAsBitmap="false" and cachePolicy="off" didn't helped (as we know caching as bitmap in Flex is buggy). After small investigation I got to mx.core.Container.updateDisplayList method:


override protected function updateDisplayList(unscaledWidth:Number,
unscaledHeight:Number):void
{
super.updateDisplayList(unscaledWidth, unscaledHeight);

..............

var backgroundColor:Object = enabled ?
null :
getStyle("backgroundDisabledColor");

if (backgroundColor === null || isNaN(Number(backgroundColor)))
backgroundColor = getStyle("backgroundColor");

..............

contentPane.cacheAsBitmap = (backgroundColor != null);
}

After looking at the last command in this method I got back to my code with VBox and found next style property - backgroundColor="0xffffff". After removing it, scrolling issue vanished.

If there is a need to set background color for your VBox and get rid of this issue, you can play with backgroundAlpha style property - refer mx.core.Container.updateDisplayList method for details.