Flash: Event.PASTE Flash获取剪贴板内容 触发paste事件 how to get paste event

            contextMenu = new ContextMenu();
            contextMenu.clipboardMenu = true;
            contextMenu.clipboardItems.paste = true;
            
            var a:Sprite = new Sprite();
            a.graphics.beginFill(0);
            a.graphics.drawRect(0, 0, 500, 400);
            addChild(a);
            
            a.addEventListener(Event.PASTE, function(e:Event):void
            {
                var a:ByteArray = Clipboard.generalClipboard.getData(ClipboardFormats.RICH_TEXT_FORMAT) as ByteArray;
                trace(a.length);
            });