如何使mx.controls.alert以<s:window/>组件为中心

我有一个MXML组件“PresentationWindow”,这是为了简洁起见,只需:

<fx:Script>
    //... functions here will be explained below
</fx:Script>
<s:Window>
    <mx:Canvas id="presentationCanvas" width="100%" height="100%">
        <mx:Button label="Test" width="100" height="25" left="0" top="100" />
    </mx:Canvas>
</s:Window>

我正试图得到一个 MX.Controls.警报 如果用户试图在窗口中退出,则在窗口上居中显示 StageDisplayState.Full_屏幕_Interactive . 我很容易让警报出现,停止/允许退出工作的功能,但警报窗口本身不会正确居中。

当前,在cmd/ctrl+q上,我将窗口退出全屏模式,防止窗口关闭事件,并显示警告(如果我将其保留在全屏模式下,则会出现相同的错误行为):

Alert.show("Are you sure you want to quit with a presentation in progress?", 
    "Quit?", (Alert.YES | Alert.NO), presentationCanvas, alertHandler);

我试过以“this”为中心,在NativeWindow对象上,现在在占整个窗口的PresentationCanvas上;但是,在所有情况下,我都会 this glorious centering effect (无论按钮是否在画布对象中)。

我还尝试将事件侦听器添加到窗口 事件.全屏 ,因此无论您是进入还是退出全屏,如果存在警报窗口,请使用 PopupManager.CenterPopup()。 试图使警报居中。

没有什么能把那个警报窗口移到我窗口的中间。

有什么想法吗?(以下是完整的actionscript,我当前尝试居中失败…)

<fx:Script>
    <![CDATA[
        import mx.controls.Alert;
        import mx.managers.PopUpManager;
        import mx.events.CloseEvent;

        private var alert:Alert;

        private function windowInit():void {
            stage.scaleMode = StageScaleMode.NO_SCALE;
            stage.align = StageAlign.TOP;
            stage.displayState = StageDisplayState.FULL_SCREEN_INTERACTIVE;

            nativeWindow.addEventListener(Event.CLOSING, preventCloseIfFullScreen);
        }

        protected function preventCloseIfFullScreen(e:Event):void {
            if (stage.displayState == StageDisplayState.FULL_SCREEN_INTERACTIVE) {
                e.preventDefault();
                stage.addEventListener(Event.FULLSCREEN, adjustAfterFullScreen);
                alert = Alert.show("Are you sure you want to quit with a presentation in progress?", "Quit?", (Alert.YES | Alert.NO), presentationCanvas, alertHandler);
                //stage.displayState = StageDisplayState.NORMAL;
            }
        }

        protected function adjustAfterFullScreen(e:FullScreenEvent):void {
            if (alert) {
                Alert.show("hi");
                PopUpManager.centerPopUp(alert);
            }
        }

        protected function alertHandler(e:CloseEvent):void {
            if (e.detail == Alert.YES) {
                NativeApplication.nativeApplication.exit();
            }
            else {
                stage.displayState = StageDisplayState.FULL_SCREEN_INTERACTIVE;
            }
        }
    ]]>
</fx:Script>