frameworks/projects/spark/asdoc/en_US/spark/components/examples/DataGroupVirtualizationExample.mxml

<?xml version="1.0" encoding="utf-8"?>
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  this work for additional information regarding copyright ownership.
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      http://www.apache.org/licenses/LICENSE-2.0

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  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.

-->
<!-- Simple example to demonstrate a DataGroup with a virtualized layout. -->
<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;

            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:Scroller>
        <s:DataGroup width="600" height="200" 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>
                            <mx:State name="normal" />
                            <mx:State name="hovered" />
                            <mx: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:Application>