Tour de Flex经典例子（二）----DataGroup(包含ItemRenderer重构

<?xml version="1.0" encoding="utf-8"?>
<!-- Simple example to demonstrate a DataGroup with a virtualized layout. 
Written by Flex 4 Team
-->
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
			   xmlns:mx="library://ns.adobe.com/flex/mx"
			   xmlns:s="library://ns.adobe.com/flex/spark">
	
	<fx:Script>
		<![CDATA[
			import mx.collections.ArrayCollection;
			
			import skins.TDFPanelSkin;
			
			public function generateDataProvider(nItems:int = 10000):ArrayCollection {
				var ac:ArrayCollection = new ArrayCollection();
				
				var sources:Array = ['San Francisco','New York','Vancouver','Denver','Hong Kong'];
				var destinations:Array = ['London','Houston','Orlando','Los Angeles','Seattle'];
				var airlines:Array = ['Green Jet','Orange Jet','Yellow Jet','Blue Jet','Red Jet'];
				var dates:Array = ['March 23-29','April 23-29','May 1-3','May 10-13','June 6'];
				
				// create a collection of random flights
				for (var i:int = 0; i < nItems; i++){
					var temp:Object = new Object();
					var random:int = Math.random() * 5;
					
					temp.start = sources[random];
					temp.end = destinations[random];
					temp.details = dates[random] + ',' + airlines[random] + " (Flight " + i + ")";
					ac.addItem(temp);
				}
				
				return ac;
				
			}
		]]>
	</fx:Script>
	
	<s:Panel title="DataGroup with Virtual Layout" 
			 width="100%" height="100%"
			 skinClass="skins.TDFPanelSkin">
		
		<s:Scroller horizontalCenter="0" top="10">
			<s:DataGroup width="600" height="123" clipAndEnableScrolling="true" dataProvider="{generateDataProvider(9000)}">
				<s:layout>
					<s:VerticalLayout gap="1" useVirtualLayout="true" />
				</s:layout>
				<s:itemRenderer>
					<fx:Component>
						<s:ItemRenderer width="600" height="20">
							<s:states>
								<s:State name="normal" />
								<s:State name="hovered" />
								<s:State name="selected" />
							</s:states>
							
							<fx:Script>
								<![CDATA[
									override public function set data(value:Object):void {
										super.data = value;
										
										if (data == null) // a renderer's data is set to null when it goes out of view
											return;
										
										txtStart.text = data.start;
										txtEnd.text = data.end;
										txtDetails.text = data.details;
									}
								]]>
							</fx:Script>
							
							<s:transitions>
								<mx:Transition fromState="normal" toState="hovered">
									<s:Animate target="{flightPlan}" duration="200">
										<s:SimpleMotionPath property="width" />
									</s:Animate>
								</mx:Transition>
								<mx:Transition fromState="hovered" toState="normal">
									<s:Animate target="{flightPlan}" duration="200" >
										<s:SimpleMotionPath property="width" />
									</s:Animate>
								</mx:Transition>
							</s:transitions>
							
							<s:Rect left="0" right="0" top="0" bottom="0" radiusX="5" radiusY="5">
								<s:fill>
									<s:SolidColor color="#E1ECF4" />
								</s:fill>
							</s:Rect>
							
							<s:HGroup verticalAlign="middle">
								<s:Group id="flightPlan" height="20" width="300" width.hovered="330">
									<s:Rect left="0" right="0" top="0" bottom="0" radiusX="5" radiusY="5">
										<s:fill>
											<s:SolidColor color="#65A3CE" color.hovered="#65A3FF" />
										</s:fill>
									</s:Rect>
									<s:Label id="txtStart" color="#FFFFFF" fontWeight="bold" left="20" verticalCenter="2" />
									<s:Label id="txtEnd" color="#FFFFFF" fontWeight="bold" right="20" verticalCenter="2" textAlign="right" />
								</s:Group>
								<s:Label id="txtDetails" color="#32353f" fontSize="11" />
							</s:HGroup>
						</s:ItemRenderer>
					</fx:Component>
				</s:itemRenderer>
			</s:DataGroup>
		</s:Scroller>    
		<s:Label width="90%" horizontalCenter="0" color="#323232" bottom="40"
				 text="Flex 4 DataGroups support virtualization. Virtualization is an optimization for layout and rendering 
				 that reduces the footprint and startup time for containers with large numbers of items. This sample shows how
				 virtualization can be achieved by only creating enough objects for the items currently being displayed. The 
				 useVirtualLayout property should be set on the layout object to achieve virtualization."/>
	</s:Panel>
	
</s:Application>