Flex Error #1009: Cannot access a property or method of a null object reference

I'm getting error while running a game I created with flex. I know there has been some question 开发者_高级运维about this, but my case is quite weird. I created a simple typing game that is running OK on my computer, but when I tried to deploy it online to facebook, I got those errors. I used code from the tutorial from adobe here http://www.adobe.com/devnet/facebook/articles/flex_fbgraph_pt4.html to deploy my flex game to facebook

This is the error message:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at FacebookUserStatusWeb/init()
    at FacebookUserStatusWeb/___FacebookUserStatusWeb_Application1_creationComplete()
    at flash.events::EventDispatcher/dispatchEventFunction()
    at flash.events::EventDispatcher/dispatchEvent()
    at mx.core::UIComponent/dispatchEvent()
    at mx.core::UIComponent/set initialized()
    at mx.managers::LayoutManager/doPhasedInstantiation()
    at mx.managers::LayoutManager/doPhasedInstantiationCallback()

And here is snippet of the init() function:

            protected var text1:String="Text to be typed"; //hard-coded temporarily
            protected const TIMER_INTERVAL:int = 10;
            protected var t:Timer = new Timer(TIMER_INTERVAL);
            protected var topURL:String=ExternalInterface.call('top.location.toString');
            protected function init():void
                    {
                        t.addEventListener(TimerEvent.TIMER, updateTimer);
                        ProblemText.text = new String(text1);
                        Facebook.init("<my app id>",loginHandler);
                        currentState = (topURL) ? "loggedout": "loggedoutonfacebook";
                    }

Some notes: 1.my app id is my facebook app id which I prefer not to show 2.ProblemText is a richtext which I placed the paragraph to be typed by the player. 3.I have deleted the method Application1_creationComplete() but it still appears at the error listing

And also I am curious about the errors other than the first two. What do they mean? Ah, and if it is helpful, I can post some more of the code

First: You're only seeing one error. Everything you see below the #1009 error is your stack trace, not additional errors.

The stack trace basically tells you the series of things that happened prior to the error occurring, with the most recent at the top. This is useful because often things which happen prior to the actual error you see will contribute to said error.

Second: The null object reference is occurring because something in your init() function tried to access a property in an object that doesn't exist, or an object that doesn't exist. One (slightly messy but effective) way to debug this would be to drop some trace statements in the code to see how far it gets before barfing with the error -- the idea being to isolate the specific line that's causing the problem. Once you've done that, you need to work backwards to figure out why the object or property you're trying to use is null. It could be something simple, like a typo, or it could be more complex. You'll have to sleuth it out, one way or another =)

Good luck!

Finally got the bug. Just in case people have the same case with me, what exactly happened is at my computer I simulated the game with just one state, but when I'm deploying to facebook I have several states (loggedin,loggedout,etc). In the init() I tried to access ProblemText Label that is not present in the current state.