FLEX中labelFunction的用法.

MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/02/21/creating-a-custom-label-function-on-a-flex-popupmenubutton-control/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="top"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            private function getTeams(dp:XML, leagueAbbrev:String, divisionLabel:String):XMLList {
                return dp.league.(@abbrev == leagueAbbrev).division.(@label == divisionLabel).team;
            }

            private function popUpMenuButton_labelFunc(item:Object):String {
                return item.@label + " " + item.@name;
            }
        ]]>
    </mx:Script>

    <mx:XML id="mlb" source="mlb.xml" />

    <mx:XMLListCollection id="mlbXLC"
            source="{getTeams(mlb, 'NL', 'West')}">
        <mx:sort>
            <mx:Sort>
                <mx:fields>
                    <mx:SortField name="@label"
                            caseInsensitive="true" />
                </mx:fields>
            </mx:Sort>
        </mx:sort>
    </mx:XMLListCollection>

    <mx:PopUpMenuButton id="popUpMenuButton"
            dataProvider="{mlbXLC}"
            labelFunction="popUpMenuButton_labelFunc" />

</mx:Application>

mlb.xml

 

  <?xml version="1.0" encoding="utf-8" ?> 
- <!--  http://blog.flexexamples.com/2007/12/04/sorting-xml-documents-using-an-xmllistcollection/ 
  --> 
- <root>
- <league label="American League" abbrev="AL">
- <division label="West">
  <team label="Los Angeles" name="Angels of Anaheim" /> 
  <team label="Seattle" name="Mariners" /> 
  <team label="Oakland" name="Athletics" /> 
  <team label="Texas" name="Rangers" /> 
  </division>
- <division label="Central">
  <team label="Cleveland" name="Indians" /> 
  <team label="Detroit" name="Tigers" /> 
  <team label="Minnesota" name="Twins" /> 
  <team label="Chicago" name="White Sox" /> 
  <team label="Kansas City" name="Royals" /> 
  </division>
- <division label="East">
  <team label="Boston" name="Red Sox" /> 
  <team label="New York" name="Yankees" /> 
  <team label="Toronto" name="Blue Jays" /> 
  <team label="Baltimore" name="Orioles" /> 
  <team label="Tampa Bay" name="Rays" /> 
  </division>
  </league>
- <league label="National League" abbrev="NL">
- <division label="West">
  <team label="Arizona" name="Diamondbacks" /> 
  <team label="Colorado" name="Rockies" /> 
  <team label="San Diego" name="Padres" /> 
  <team label="Los Angeles" name="Dodgers" /> 
  <team label="San Francisco" name="Giants" /> 
  </division>
- <division label="Central">
  <team label="Chicago" name="Cubs" /> 
  <team label="Milwaukee" name="Brewers" /> 
  <team label="St. Louis" name="Cardinals" /> 
  <team label="Houston" name="Astros" /> 
  <team label="Cincinnati" name="Reds" /> 
  <team label="Pittsburgh" name="Pirates" /> 
  </division>
- <division label="East">
  <team label="Philadelphia" name="Phillies" /> 
  <team label="New York" name="Mets" /> 
  <team label="Atlanta" name="Braves" /> 
  <team label="Washington" name="Nationals" /> 
  <team label="Florida" name="Marlins" /> 
  </division>
  </league>
  </root>

来自：http://blog.flexexamples.com/2008/02/21/creating-a-custom-label-function-on-a-flex-popupmenubutton-control/