You might have noticed that Window or WindowedApplication doesn’t load in the center of your screen. By default, window loads somewhere in the left side on your desktop. I personally think, that this is a bad user experience and you should always center window vertically and horizontally on screen. You can do this by setting window x coordinate to (screen.width – window.width)/2  and y coordinate to (screen.height – window.height)/2.

<?xml version="1.0" encoding="utf-8"?>
<mx:WindowedApplication xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"
    creationComplete="centerWindow(this)" viewSourceURL="srcview/index.html"> 

    <mx:Script>
        <![CDATA[
            import mx.core.Window;

            private function centerWindow(window:WindowedApplication):void
            {
                var screenBounds:Rectangle = Screen.mainScreen.bounds;
                var nativeWindow:NativeWindow  = window.nativeWindow;

                nativeWindow.x = (screenBounds.width - nativeWindow.width)/2;
                nativeWindow.y = (screenBounds.height - nativeWindow.height)/2;
            }
        ]]>
    </mx:Script> 

</mx:WindowedApplication>