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

[Cheska]

Hi,

I am referencing a button that is within another MC on my main stage. The code I have on the first frame of my movie in the actions time-line is the following:

this.slideout_MC.info_btn.addEventListener(MouseEvent.MOUSE_DOWN, myHandler);
function myHandler(event:MouseEvent):void {
    navigateToURL(new URLRequest("http://www.mywebsite.com/page2.html"), "_self");
}

And the error i keep receiving in the error panel is:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at office_fla::MainTimeline/frame1()


Can anyone please help me understand why it's saying this and to figure out how to make my button work?

Thanks in advance of any suggestions/advice,

Cheska


PS) Eventually i will have 6 buttons referenced in the same way. this seems like an awful lot of code compared to the old way of getting buttons to work in MX, albeit i understand code in the time-line is better than on the stage.. but still seems like a lots of code per button.

[cancerinform]

Do a trace:
trace(slideout_MC.info_btn);
and see what you get.

[Cheska]

Hi Cancerinform and thanks for trying to help me out.

If I place the trace directly after the button event code on frame one, nothing happens. No trace output and no compiler errors.

If I place the trace after the stop(); command on frame 20 within the actual slideout_MC (the last frame), I still get no trace but I get a compiler error:

1120: Access of undefined property slideout_MC.

??

Cheska

[cancerinform]

If you don't get any trace output, the error has occurred before. So place the trace above the button event code or further above until you get a trace.

[Cheska]

If I place the button directly on the stage on the first frame of the movie, and reference that one in my button code instead (rather than the instance within the slideout_MC ), and use the following code on the first frame:

info_btn.addEventListener(MouseEvent.MOUSE_DOWN, myHandler);
function myHandler(event:MouseEvent):void {
    navigateToURL(new URLRequest("http://www.mywebsite.com/page2.html"), "_self");
}

Then it works!

So my original code just can't find my button when it's inside slideout_MC ...

But I do need it to be in slideout_MC

What can I do to fix this?

PS) I use the target helper in my actions pane to locate the info_btn in my slideout_MC , so the path is correct.

[Cheska]

Hi Cancerinform,

I can't get a trace output no matter where i put the trace.

There are only two pieces of code in my whole movie.

The button code on very first frame of the main stage.

and the stop(); code on the last frame of the slideout_MC.

the slideout_MC is the only MC on the stage.

I can't seem to get a trace output using that trace code no matter where i put it...?

[Cheska]

what does the compiler error mean when it says

'1120: Access of undefined property slideout_MC.'

what's the undefined property??

[cancerinform]

what does the compiler error mean when it says

'1120: Access of undefined property slideout_MC.'

what's the undefined property??

It means there is no identifier called slideout_MC. If at one point you have a line like this:
var slideout_MC:MovieClip;
then slideout_MC would be null. Have you given slideout_MC a name in the property inspector?

[Cheska]

Hi again :-)

Yes, I named it slideout_MC in the property inspector.

Usually when i forget to give an MC an actual name in the property inspector, when using the target helper, the actions pane puts the MC in parenthesis and gives a warning that you have to name the MC to target it correctly...

but this is not the case, it is definitely named...

?

[cancerinform]

However, in frame 20 the object does not exist. Did you do trace in frame 1 of only slideout_MC? Sorry if it sounds stupid, but do you really have info_but in that MovieClip and named? You can also try
trace(slideout_MC.getChildByName("info_but"));

[Cheska]

There's no way you sound stupid. I'm sure I'm the stupid one here...

However, yes it is definitely named info_btn.

Though info_btn doesn't actually exist in the movie until about frame 10 of slideout_MC.

I've managed to get it to work by putting the button event code on line 20 of the slideout_MC.

But I thought the whole idea was to have all code (other than stop(); commands) on the first frame of the movie. I thought that was the entire concept of AS3. So that's why I was trying to put the code on frame 1 of my main time-line. I don't understand why the target path wasn't working.

I understand why flash is evolving, all for the better and all that... I can't say i'm thrilled about it taking me near a week to accomplish what used to take 2 seconds in MX!!

I now have something akin to this on frame 20 of my slideout_MC, which seems like a crazy amount of code to get 4 buttons to click to 4 URLS:

info_btn.addEventListener(MouseEvent.MOUSE_DOWN, myHandler);
function myHandler(event:MouseEvent):void {
    navigateToURL(new URLRequest("information.html"), "_self");
}

specialized_btn.addEventListener(MouseEvent.MOUSE_DOWN, myHandler2);
function myHandler2(event:MouseEvent):void {
    navigateToURL(new URLRequest("specialized.html"), "_self");
}

collaborative_btn.addEventListener(MouseEvent.MOUSE_DOWN, myHandler3);
function myHandler3(event:MouseEvent):void {
    navigateToURL(new URLRequest("collaborative.html"), "_self");
}

test_btn.addEventListener(MouseEvent.MOUSE_DOWN, myHandler4);
function myHandler4(event:MouseEvent):void {
    navigateToURL(new URLRequest("testimonials.html"), "_self");
}

Thank so much for your help cancerinform. I really appreciate it. I wouldn't have figured it out this far without you.

[cancerinform]

Though info_btn doesn't actually exist in the movie until about frame 10 of slideout_MC.

That is the problem of using frames. In frame one the compiler does not know that in frame 10 there is a button. And in frame 20 there is no movieclip so the compiler gives you an error.

If you don't want certain objects to be shown until a certain frame, make them invisible.