How do you run loop functions on specific frames of nested Movieclips?

Question

I'm still pretty new to AS3 and I've run into a problem that I never had with AS2.  I have a project where the 1st frame of the main timeline is the loading screen and the second frame has buttons and a title bar that I want to be on every "page" of my project.  There are 7 buttons that take the user between 7 different "pages", which consist of 7 frames of a movieclip I have filling the content area on frame 2 of my main timeline.  I'll call this movieclip "pages_mc".
The problem is that frame 6 of the pages_mc movieclip has the following code:
var moving = 0;
var xmoved;
var xbegin = pano_cont.pano_image.x;
parts_mc.addEventListener(Event.ENTER_FRAME, moveImage); // constantly moves the image 1 pixel left or right depending on the button pressed
btn_left.addEventListener(MouseEvent.MOUSE_DOWN, moveLeft); //changes the variable "moving" to 2 on mouse down
btn_right.addEventListener(MouseEvent.MOUSE_DOWN, moveRight); //changes the variable "moving" to 1 on mouse down
btn_left.addEventListener(MouseEvent.MOUSE_UP, stopMoveLeft); //changes the variable "moving" to 0 on mouse up
btn_right.addEventListener(MouseEvent.MOUSE_UP, stopMoveRight); //changes the variable "moving" to 0 on mouse up
function moveImage(e.Event):void{
xmoved = xbegin - pano_cont.pano_image.x;
    if(moving == 1)
        pano_cont.pano_image.x -= 1;
    if(moving == 2)
        pano_cont.pano_image.x += 1;
    if(xmoved < -(pano_cont.pano_image.width/2)+180)
        pano_cont.pano_image.x = -2538;
    if(xmoved > (pano_cont.pano_image.width/2)- 180)
        pano_cont.pano_image.x = -2178;
function moveRight (e:MouseEvent):void
    btn_right.gotoAndStop("down");
    moving = 1;
function moveLeft (e:MouseEvent):void
    btn_left.gotoAndStop("down");
    moving = 2;
function stopMoveLeft (e:MouseEvent):void
    moving = 0;
    btn_left.gotoAndStop("active");
function stopMoveRight (e:MouseEvent):void
    moving = 0;
    btn_right.gotoAndStop("active");
This is all just some code to allow users to move a panaromic image around on the screen.  But when I navigate to a different page from of my pages_mc movieclip I get the following output message:
TypeError: Error #1099: Cannot access a property or method of a null object reference.
     at SampleProject_fla::Content_MC_1/moveImage()
I'm thinking this is happening because the "parts_mc" movieclip I referenced for the ENTER_FRAME event listener no longer exists (unless you go back to frame 6 of pages_mc).  I'm not sure how to remove this event listener when the user moves to another frame of pages_mc.
Any help would be greatly appreciated.

Answer 1

kglad wrote:
what's parts_mc.parts_mc???
Not sure where you see that.  I see pages_mc.parts_mc which is just because the parts_mc movieclip is nested on the 6th frame of the pages_mc movieclip.
At any rate, I was able to get it working by moving all the code onto frame 2 of the main timline and declaring all of my vairables on frame 1 of the main timeline.  I then added an ENTER_FRAME event listener onto one of my movieclip buttons (main_btn) on the main timeline and had it check what frame the pages_mc movieclip was on.  If it was frame 6, I then executed the moveImage function and had it remove the event listener from the main_btn movieclip if the frame changed away from frame 6.
Seems to be working so far.
Here's the code:
Frame 1
/* Declaring variables. */
var pagenumber:Number;
var moving:Number = 0;
var firstTime:Number = 0;
var xmoved:Number;
var xbegin:Number;
Frame 2
pages_mc.addEventListener(Event.ENTER_FRAME, pageNum);
pages_mc.addEventListener(Event.ENTER_FRAME, BtnSelParts);
/* Keeps track of current page. */
function pageNum(e:Event):void
    pagenumber = pages_mc.currentFrame;
    title_bar.gotoAndStop(pages_mc.currentFrame);
function BtnSelParts(e:Event):void
    if(pagenumber == 6)
        btn_parts.gotoAndStop("current");
        if(firstTime == 0)
            btn_main.addEventListener(Event.ENTER_FRAME, moveImage); //moves the panorama image left or right
    else
        if(btn_parts.currentFrame == 32)
            btn_parts.gotoAndStop(1);
function moveImage(e:Event):void
    if(pagenumber==6)
        if(firstTime == 0)
            pages_mc.btn_left.addEventListener(MouseEvent.MOUSE_OVER, overLeft); //animates left arrow button on rollover
            pages_mc.btn_right.addEventListener(MouseEvent.MOUSE_OVER, overRight); //animates right arrow button on rollover
            pages_mc.btn_left.addEventListener(MouseEvent.MOUSE_DOWN, moveLeft); //changes the variable "moving" to 2 on mouse down
            pages_mc.btn_right.addEventListener(MouseEvent.MOUSE_DOWN, moveRight); //changes the variable "moving" to 1 on mouse down
            pages_mc.btn_left.addEventListener(MouseEvent.MOUSE_UP, stopMoveLeft); //changes the variable "moving" to 0 on mouse up
            pages_mc.btn_right.addEventListener(MouseEvent.MOUSE_UP, stopMoveRight); //changes the variable "moving" to 0 on mouse up
            pages_mc.btn_left.addEventListener(MouseEvent.MOUSE_OUT, rollOutLeft); //animates left arrow button on rollout
            pages_mc.btn_right.addEventListener(MouseEvent.MOUSE_OUT, rollOutRight); //animates right arrow button on rollout
            xbegin = pages_mc.parts_mc.pano_image.x;
            firstTime = 1;
        xmoved = xbegin - pages_mc.parts_mc.pano_image.x;
        if(moving == 1)
            pages_mc.parts_mc.pano_image.x -= 1;
        if(moving == 2)
            pages_mc.parts_mc.pano_image.x += 1;
        if(xmoved < -(pages_mc.parts_mc.pano_image.width/2)+180)
            pages_mc.parts_mc.pano_image.x = -2538;
        if(xmoved > (pages_mc.parts_mc.pano_image.width/2)- 180)
            pages_mc.parts_mc.pano_image.x = -2178;
        if(pages_mc.parts_mc.pano_image.pano1.currentFrame == 1)
            pages_mc.btn_sel.gotoAndStop(1);
        if(pages_mc.parts_mc.pano_image.pano1.currentFrame == 2)
            pages_mc.btn_sel.gotoAndStop(2);
        if(pages_mc.parts_mc.pano_image.pano1.currentFrame == 3)
            pages_mc.btn_sel.gotoAndStop(3);
    else
        btn_main.removeEventListener(Event.ENTER_FRAME, moveImage);
        firstTime = 0;
} // controlls the panaromas
Let me know if you see any problems with this.
Thanks again.