Sunday, October 12, 2008

Item Renderer in Flex

Adobe Flex supports several controls that you can use to represent lists of items. These controls let the application user scroll through the item list and select one or more items from the list. All Flex list components are derived from the ListBase class, and include the following controls: DataGrid, HorizontalList, List, Menu, TileList, and Tree.

Each list control has a default mechanism for controlling the display of data, or view, and lets you override that default. To override the default view, you create a custom item renderer.

The following example shows how you can create a simple TileList item renderer which displays custom items with an icon and a label in the TileList control’s tiles.

rowHeight="100" />

TileListItemRenderer is an item renderer class which is defined in an MXML file named TileListItemRenderer.mxml as shown below:

<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:mx="">
<mx:Image source="{data.@src}" horizontalCenter="0" verticalCenter="0" />
<mx:Label text="{data.@lbl}" fontWeight="bold" horizontalCenter="0" bottom="0" />

If you want to make a TileList control use this renderer, and have each renderer instance display an image and a label, you would write the following code:
var itemRenderer:ClassFactory = new ClassFactory(TitleListItemRenderer);
myTileList.itemRenderer = itemRenderer;

However, in MXML, you can use the following syntax:

and the MXML compiler automatically creates the ClassFactory instance for you.
At runtime, Flex uses it to generate instances of item renderer class (i.e.,

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