這是一個flex對象失去焦點的典型

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/02/29/determining-if-a-flex-application-has-focus-using-the-activate-and-deactivate-events/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white"
        activate="application_activate(event);"
        deactivate="application_activate(event);">

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

            private function application_activate(evt:Event):void {
                arrColl.addItemAt({type:evt.type, time:getTimer()}, 0);
            }

            private function time_labelFunc(item:Object, col:DataGridColumn):String {
                return numberFormatter.format(item[col.dataField]);
            }
        ]]>
    </mx:Script>

    <mx:ArrayCollection id="arrColl" />

    <mx:NumberFormatter id="numberFormatter"
            useThousandsSeparator="true" />

    <mx:DataGrid id="dataGrid"
            dataProvider="{arrColl}"
            width="320"
            rowCount="8"
            verticalScrollPolicy="on">
        <mx:columns>
            <mx:DataGridColumn dataField="type" />
            <mx:DataGridColumn dataField="time"
                    headerText="time (ms)"
                    labelFunction="time_labelFunc" />
        </mx:columns>
    </mx:DataGrid>

</mx:Application>