<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/02/26/displaying-a-tree-control-as-a-pop-up-for-a-flex-popupbutton-control/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

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

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

    <mx:ApplicationControlBar dock="true">
        <mx:PopUpButton label="Please select a team...">
            <mx:popUp>
                <mx:Tree id="tree"
                        dataProvider="{mlb}"
                        labelField="@label"
                        showRoot="false"
                        width="200"
                        rowCount="8" />
            </mx:popUp>
        </mx:PopUpButton>
    </mx:ApplicationControlBar>

</mx:Application>