Flex中如何利用FocusManager类的setFocus函数设置TextInput的焦点的例

http://blog.minidx.com/ext04/setting-focus-in-flex-using-the-focus-manager/srcview/index.html

<?xml version="1.0" encoding="utf-8"?>
<mx:Application name="FocusManager_setFocus_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

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

            private function submitButton_click(evt:MouseEvent):void {
                Alert.show(evt.currentTarget.label,
                            Object(focusManager.getFocus()).name);
            }

            private function resetButton_click(evt:MouseEvent):void {
                username.text = "";
                password.text = "";
                Alert.show(evt.currentTarget.label,
                            Object(focusManager.getFocus()).name);
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Button label="Set focus to Username"
                click="focusManager.setFocus(username);" />
        <mx:Button label="Set focus to Password"
                click="focusManager.setFocus(password);" />
    </mx:ApplicationControlBar>

    <mx:Form id="form"
            defaultButton="{submitButton}">
        <mx:FormItem label="Username:">
            <mx:TextInput id="username" />
        </mx:FormItem>
        <mx:FormItem label="Password:">
            <mx:TextInput id="password"
                    displayAsPassword="true" />
        </mx:FormItem>
        <mx:FormItem direction="horizontal"
                horizontalAlign="right"
                width="100%">
            <mx:Button id="submitButton"
                    label="Submit"
                    click="submitButton_click(event);" />
            <mx:Button id="resetButton"
                    label="Reset"
                    click="resetButton_click(event);" />
        </mx:FormItem>
    </mx:Form>

</mx:Application>