How do I ensure a Flex dataProvider processes the data synchronously? - apache-flex

Question

I am using an component, and currently have a dataProvider working that is an ArrayCollection (have a separate question about how to make this an XML file... but I digress).
Variable declaration looks like this:
[Bindable]
private var _dpImageList : ArrayCollection = new ArrayCollection([
{"location" : "path/to/image1.jpg"},
{"location" : "path/to/image2.jpg"},
{"location" : "path/to/image3.jpg"}
]);
I then refer to like this:
<s:List
id="lstImages"
width="100%"
dataProvider="{_dpImageList}"
itemRenderer="path.to.render.ImageRenderer"
skinClass="path.to.skins.ListSkin"
>
<s:layout>
<s:HorizontalLayout gap="2" />
</s:layout>
</s:List>
Currently, it would appear that each item is processed asynchronously.
However, I want them to be processed synchronously.
Reason: I am displaying a list of images, and I want the leftmost one rendered first, followed by the one to its right, and so on.
Edit:
I just found this answer.
Do you think that could be the same issue?

Answer 1

Instead of declaring the variable and using it as the binding source, declare two collections. Then, onCreationComplete call loadNext() which shifts an object out of the second array and pushes it into the first. When the item has been rendered (custom event dispatched by itemRenderer and caught) call loadNext() again until such time as your source array is empty and your bound dataProvider has all the images.
I can write it in code if this doesn't make any sense. ;)
<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/halo" minWidth="1024" minHeight="768" creationComplete="init()">
<fx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
[Bindable]
private var _source : ArrayCollection = new ArrayCollection([
{"location" : "path/to/image1.jpg"},
{"location" : "path/to/image2.jpg"},
{"location" : "path/to/image3.jpg"}
]);
[Bindable] private var dataProvider:ArrayCollection;
protected function init():void
{
this.lstImages.addEventListener( "imageLoaded", handleImageLoaded);
loadImage()
}
protected function loadImage():void
{
if(this._source.length<=0)
return;
var image:Object = this._source.getItemAt(0);
dataProvider.addItem(image);
this._source.removeItemAt(0);
}
protected function handleImageLoaded(event:Event):void
{
loadImage()
}
]]>
</fx:Script>
<s:List
id="lstImages"
width="100%"
dataProvider="{_dpImageList}"
itemRenderer="path.to.render.ImageRenderer"
skinClass="path.to.skins.ListSkin"
>
<s:layout>
<s:HorizontalLayout gap="2" />
</s:layout>
</s:List>
</s:Application>
Your item renderer's image's complete handle will dispatch:
protected function handleImageLoaded(event:Event):void
{
owner.dispatch(new Event("imageLoaded"));
}
And that should load your images in a clean sequence.