<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/10/02/adding-a-horizontal-separator-to-a-flex-popupbutton-controls-pop-up-menu-redux/ -->
<mx:Application name="PopUpButton_popUp_dataProvider_type_test_2"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="top"
        backgroundColor="white" viewSourceURL="srcview/index.html">

    <mx:Style>
        PopUpButton {
            popUpStyleName: myCustomPopUpStyleName;
            closeDuration: 0;
            openDuration: 0;
        }

        .myCustomPopUpStyleName {
            fontWeight: normal;
            textAlign: left;
        }
    </mx:Style>

    <mx:Script>
        <![CDATA[
            import mx.controls.Menu;

            private var menu:Menu;

            private function popUpButton_initialize():void {
                menu = new Menu();
                menu.dataProvider = arr;
                menu.variableRowHeight = checkBox.selected;
                popUpButton.popUp = menu;
                popUpButton.open();
            }

            private function checkBox_change(evt:Event):void {
                menu.variableRowHeight = checkBox.selected;
                menu.invalidateSize();
                popUpButton.open();
            }
        ]]>
    </mx:Script>

    <mx:Array id="arr">
        <mx:Object label="One" />
        <mx:Object label="Two" />
        <mx:Object label="Three" />
        <mx:Object type="separator" />
        <mx:Object label="The quick brown fox jumped over the lazy dog." />
    </mx:Array>

    <mx:ApplicationControlBar dock="true">
        <mx:CheckBox id="checkBox"
                label="variableRowHeight:"
                labelPlacement="left"
                selected="true"
                change="checkBox_change(event);" />
    </mx:ApplicationControlBar>

    <mx:PopUpButton id="popUpButton"
            label="PopUpButton with separator"
            openAlways="true"
            initialize="popUpButton_initialize();" />

</mx:Application>