CODEWITHSUNDEEP
actionscript-3nullflash
Joe Slater
Joe Slater

Reputation: 2473

What is the null-object error with this AS3 code for loading external swf?

I am getting a null object error when I add the mouse event listener for the log in button. (Look at the comments in the constructor)

I am using Flash CS6, and objects such as logInbutton and screen_log_in are instance names from the .fla file. This here is the .as file.

Error I get is:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at actions::indexPage()

My AS3 code:

package actions
{
    import flash.display.MovieClip;
    import flash.events.Event;
    import flash.events.ProgressEvent;
    import flash.events.IEventDispatcher;
    import flash.net.URLRequest;
    import flash.display.Loader;
    import fl.motion.MotionEvent;
    import flash.events.MouseEvent;

public class indexPage extends MovieClip
{
    public function indexPage():void
    {
        loadSWF("http://mathlympics.cu.cc/loginsystem.swf");

        //THIS IS THE LINE WHICH IS CAUSING THE ERROR
        //WHEN I COMMENT IT OUT THE ERROR IS GONE
        logInButton.addEventListener(MouseEvent.CLICK, goToLogIn);
    }

    var _swfLoader:Loader;
    var _swfContent:MovieClip;

    public function loadSWF(path:String):void 
    {
       var _req:URLRequest = new URLRequest();
       _req.url = path;

       _swfLoader = new Loader();
       setupListeners(_swfLoader.contentLoaderInfo);

       _swfLoader.load(_req);
    }

    function setupListeners(dispatcher:IEventDispatcher):void 
    {
       dispatcher.addEventListener(Event.COMPLETE, addSWF);
    }

    function addSWF(event:Event):void 
    {
       event.target.removeEventListener(Event.COMPLETE, addSWF);
       event.target.removeEventListener(ProgressEvent.PROGRESS, preloadSWF);
       _swfContent = event.target.content;
       screen_log_in.addChild(_swfContent);
    }

    function unloadSwf():void
    {
        _swfLoader.unloadAndStop();
        screen_log_in.removeChild(_swfContent);
        _swfContent = null;
    }

    function goToLogIn(e:MouseEvent):void
    {
        unloadSwf();
        screen_log_in.loadSWF("http://mathlympics.cu.cc/loginsystem.swf");
    }

    function goToRegister(e:MouseEvent):void
    {
        unloadSwf();
        screen_log_in.loadSWF("http://mathlympics.cu.cc/register.swf");
    }
    }
}

Upvotes: 1

Views: 519

Answers (2)

Joe Slater
Joe Slater

Reputation: 2473

I am just going to answer my question for the future visitors. The cause of problem I have note been able to figure out but what I have figured out is how to get around it. I simply copy pasted my code from document class to the frames and it works absolutely fine there.

Upvotes: 0

The_asMan
The_asMan

Reputation: 6403

You can not access stage until stage is available.

public function indexPage():void
{
    addEventListener(Event.ADDED_TO_STAGE,init)
}

public function init(e:Event):void
{
    removeEventListener(Event.ADDED_TO_STAGE,init)
    loadSWF("http://mathlympics.cu.cc/loginsystem.swf");

    //THIS IS THE LINE WHICH IS CAUSING THE ERROR
    //WHEN I COMMENT IT OUT THE ERROR IS GONE
    logInButton.addEventListener(MouseEvent.CLICK, goToLogIn);
}

Upvotes: 2

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