AS3: repeating function in sigle frame timeline - actionscript-3

Question

I'm very new in action script. I have single frame timeline and there is function that moves movie clip verticaly. i want to repeat this only three times.
The code works, I'm just not sure if this is the correct way or if it's too complicated.
var pocet:Number = 0;
pruh.addEventListener(Event.ENTER_FRAME, fl_AnimateVertically);
function fl_AnimateVertically(event:Event)
{
if (pruh.y >= stage.stageHeight) {
pocet++;
}
if (pruh.y < stage.stageHeight) {
pruh.y += 3;
}
else {
pruh.y = 0 - pruh.y;
}
if (pocet == 3) {
pruh.removeEventListener(Event.ENTER_FRAME, fl_AnimateVertically);
}
}
thanx

Answer 1

Congratulations on achieving your goal.
Your code could be improved in terms of readability. You have fl_AnimateVertically as a descriptive name, but other than that it's kind of hard to figure out what's going on exactly. I mean sure it adds 3 to y which probably results in movement, but it's not trivial to understand the exact behaviour.
That's why you want to use abstraction or more of a top down approach as it often called..
What you are doing at the moment is adding a value to the coordinate, which as a result creates an animation. What you actually want is to create an animation, without going into details what that actually means.
And sure enough, people created animations with code before. That's why you can create an animation in the abstract sense: An animation is the change of a property of an object over time. In the realm of flash an animation is called a tween and there's a class doing exactly that..
Let's take the example code there:
var myTween:Tween = new Tween(myObject, "x", Elastic.easeOut, 0, 300, 3, true);
And apply it to your situation.
var verticalAnimation:Tween = new Tween(pruh, "y", Elastic.easeOut, pruh.y, stage.stageHeight, 3, true);
You have to adjust the duration to your liking. I hope you see how this is easier to read and maintain, because you specify properties of the animation like duration. You can also specify easing, which makes the motion more interesting.
Ok, this is only one animation, but you want 3, right?
More precisely, you want to do that same animation again, when it finished.
And you can do exactly that:
var animationCount:uint = 0;
var verticalAnimation:Tween = new Tween(pruh, "y", Elastic.easeOut, pruh.y, stage.stageHeight, 3, true);
verticalAnimation.addEventListener(TweenEvent.MOTION_FINISH, onMotionFinish); // wait for the animation to be finished
function onMotionFinish(e:TweenEvent):void
{
animationCount++; // add 1 to the counter
if(animationCount >= 3) // check how many times the animation finished so far
{
// if it was the last one, remove the listener
verticalAnimation.removeEventListener(TweenEvent.MOTION_FINISH, onMotionFinish);
}
else
{
// otherwise rewind and start again
verticalAnimation.rewind();
verticalAnimation.start();
}
}
There are other libraries than this built in Tween class that are far more powerful.
The one from greensock is very popular and easy to use you can find the documentation for the flash version here

Answer 2

Try this
var pocet:Number = 0;
pruh.addEventListener(Event.ENTER_FRAME, fl_AnimateVertically);
var startY:int=pruh.y;
function fl_AnimateVertically(event:Event)
{
if (pruh.y >= stage.stageHeight) {
pocet++;
pruh.y=startY;
}
if (pruh.y < stage.stageHeight) {
pruh.y += 3;
}
else {
pruh.y = 0 - pruh.y;
}
if (pocet ==3) {
pruh.removeEventListener(Event.ENTER_FRAME, fl_AnimateVertically);
trace("done");
}
}