Simple App - Huge Lag. Please Help.

Question

So I have built a simple app that has 40 frames in the timeline. On each of those frames, I have an 2 images (PNG format) at 320x480 that come in at about 15kb each. I also have a block of text and 3 buttons. One button calls to an event that sets the visibility of the top image to 0, revealing the image underneath. Another click of that button sets the image visibility back to 1. The other 2 buttons control clicking back and forth between frames (previous and next buttons). Altogether I have 100 PNG image files in my app. I have imported the images into the library and they are physically in the timeline as opposed to being pulled in via ActionScript. The ActionScript for the buttons is done once and stretches across all 40 frames - it is:
btnMagnify.addEventListener(MouseEvent.CLICK, onClickMag);
btnPrev.addEventListener(MouseEvent.CLICK, onClickPrev);
btnNext.addEventListener(MouseEvent.CLICK, onClickNext);
function onClickMag(event:MouseEvent):void {
    if(myZoom == 0){
        imagefull.visible = false;
        myZoom = 1;
    } else {
        imagefull.visible = true;
        myZoom = 0;
function onClickPrev(event:MouseEvent):void {
    var myNum = currentLabel.split("-");
    gotoAndStop("pg-" + (int(myNum[1]) - 1));
function onClickNext(event:MouseEvent):void {
    var myNum = currentLabel.split("-");
    gotoAndStop("pg-" + (int(myNum[1]) + 1));
My problem is that when I export this to my iPhone, it takes about 4 seconds when I click on one of those buttons before it reacts and does what I want. If I cut down the number of frames (and, thus, images used) it increases the speed at which it performs. Should I be loading these images into the movie in a different manner so performace can be optimized on the iPhone? I've been working with Flash for several years, but this is my first iPhone app using it and I can't understand why the SWF works fine but the iPhone app is so slow. Any help or advice would be GREATLY appreciated.
Thanks!

Answer 1

Forget the timeline and do something like this:
Import your images to library and turn on Export for Actionscript, name your images and create an array:
     private var bgImgArr                    :Array = new Array("bg_abstract", "bg_bamboo", "bg_bars", "bg_candy");
Write a method similar to this:
        private function setBgImage(str:String):void
            if (currentBgImg && this.contains(currentBgImg) ) removeChild(currentBgImg);
            var bgClassReference:* = getDefinitionByName(str);
            var bgInstance:BitmapData = new bgClassReference();
            currentBgImg = new Bitmap( bgInstance );
            addChild(currentBgImg);
Call it like this:
setBgImage(bgImgArr[ SOME_INDEX ]);
Runs smoothly on iPhone 3G with any number of images. I just used similar approach in my latest iPhone game Blockslide: http://itunes.apple.com/us/app/blockslide/id431490534?mt=8&ls=1