Custom PopUp and Modal Dialog in Flex

<?xml version="1.0" encoding="utf-8"?>
<mx:TitleWindow xmlns:mx="http://www.adobe.com/2006/mxml" title="My Dialog" showCloseButton="true" close="closeDialog(event)">
   <mx:Script>
       <![CDATA[
          import mx.managers.PopUpManager;
          import mx.events.CloseEvent;

          private function closeDialog(event : CloseEvent) : void {
             PopUpManager.removePopUp(this); // close this dialog
          }
       ]]>
   </mx:Script>
   <mx:VBox>
      <mx:TextInput id="input" />
      <mx:Button label="OK" click="closeDialog(null)"/>
   </mx:VBox>
</mx:TitleWindow>

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">
   <mx:Script>
       <![CDATA[
          import mx.managers.PopUpManager;

          private function showDialog() : void {
             PopUpManager.createPopUp(this, MyDialog, true); // popup modal dialog
          }
       ]]>
   </mx:Script>
   <mx:Button label="Open Modal Dialog" click="showDialog()"/>
</mx:Application>