Click button to play and click to reverse

Question

I have a test button i would like to have play a movie where a graphic expands. Once stopped, I would like to be able to click that same button and have the graphic go backwards. I would prefer to have timeline reverse, rather than lengthen the timeline of the mc because then i have to line up the start and end, and if one changes, i have to remember to change the other.
I have:
btn_test.onRelease = function(){
    if (_root.adinstance._currentframe != 1) {
        while(_root.adinstance._currentframe != 1) {
            _root.adinstance.prevFrame();
    else {   
        _root.adinstance.play();
I get the expand, but when when it hits the while loop, it just disappears the adinstance mc.
Any ideas?

Answer 1

You rarely want to use any kind of coded loop to animate something, especially a while loop (they can be especially ornery).  Try something more along the lines of....
btn_test.onRelease = function(){
    if (_root.adinstance._currentframe != 1) {
        _root.adinstance.onEnterFrame = function(){
             if(_root.adinstance._currentframe != 1){
                   _root.adinstance.prevFrame();
             } else {
                   delete _root.adinstance.onEnterFrame;
    else {   
        _root.adinstance.play();