Binding to Container children in Flex

I guess this week is my week for creating AS3/Flex hacks. I created an XML encoder/decoder that will accept a class-map and create your model from your XML and visa-versa. As part of that I have display objects as part of the model that needs saving out. I suppose you could liken it to MXML. In order for the XML encoder to work with DisplayObjectContainers I had to give it a way to work with an ArrayCollection to add or remove the children. So I subclassed LayoutContainer and gave it a property called “children” which is an ArrayCollection. Then I set up as a listener to it and every time something is added or removed I use the corresponding DisplayObjectContainer methods to update the display. Pretty slick! The only downside is that someone could add anything to the children ArrayCollection and

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break things since I am expecting DisplayObjects only. I could add error checking and make it fix itself when that happens… maybe another time. Here’s my listener which responds to the “collectionChange” event of children:

 protected function onChildrenChange(event:CollectionEvent):void { var i:Number; var items:Array = event.items; var location:Number = event.location; var oldLocation:Number = event.oldLocation; var numItems:Number = items.length; var child:DisplayObject; var propChange:PropertyChangeEvent; switch (event.kind) { case CollectionEventKind.ADD: for (i = 0; i < numItems; i++) { child = items[i] as DisplayObject; if (child) addChildAt(child, location + i); } break; case CollectionEventKind.REMOVE: for (i = 0; i < numItems; i++) { child = items[i]; if (child) removeChild(child); } break; case CollectionEventKind.MOVE: setChildIndex(getChildAt(oldLocation), location); break; case CollectionEventKind.REPLACE: for (i = 0; i < numItems; i++) { propChange = items[i] as PropertyChangeEvent; var oldChild:DisplayObject = propChange.oldValue as DisplayObject; var newChild:DisplayObject = propChange.newValue as DisplayObject; if (oldChild && newChild) { var index:Number = getChildIndex(oldChild); removeChildAt(index); addChildAt(newChild, index); } } break; case CollectionEventKind.REFRESH: removeAllChildren(); for each (child in _children) addChild(child); break; case CollectionEventKind.RESET: removeAllChildren(); for each (child in _children) addChild(child); break; case CollectionEventKind.UPDATE: // don't need to do anything break; } } 

2 Responses to “Binding to Container children in Flex”

  1. 3 wheeler buggy Says:

    You can not believe how long ive been searching for something like this. Scrolled through 7 pages of Yahoo results without finding anything. One search on Bing. There was this… Really have to start using it more often!

  2. Jenlteby Says:

    Niksduer say: What for mad thought?

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