Titanium开发遇到的一个‘isn't already in the context’ 错误

错误：
Adding an event listener to a proxy that isn't already in the context。

用 navGroup打开一个window，然后新建leftnavbutton,并注册事件，会报错：
Adding an event listener to a proxy that isn't already in the context。

一步步删代码，发现是事件注册问题。。
网上资料：http://developer.appcelerator.com/question/135176/error-adding-an-event-listener-to-a-proxy-that-isnt-already-in-the-context#answer-237243

“A quick and dirty fix for this issue is to set the backgroundGradient AFTER you have created the button and added it to a view. This will put the button into the context and prevent this message from displaying.”

我觉得这句话有点道理，所以我加了settimeout来延时注册 button的事件，有一定效果额~

不知道这么做会有什么后遗症。。。

setTimeout(function() {
        leftButton.addEventListener("click", function() {
            currentWindow.fireEvent("closeWindow");
        });
    }, 50);

.