Titanium開發遇到的一個‘isn't already in the context’ 錯誤

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

用 navGroup打開一個window，然後新建leftnavbutton,並註冊事件，會報錯：
Adding an event listener to a proxy that isn't already in the context。

一步步刪代碼，發現是事件註冊問題。。
網上資料：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.”

我覺得這句話有點道理，所以我加了settimeout來延時註冊 button的事件，有一定效果額~

不知道這麼做會有什麼後遺症。。。 8)

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