sequential drawing / animation iOS - objective-c

Question

i have an array of uibezierpath's.
how could I draw each path in sequence, but with a delay so it appears animated?
I am currently drawing the whole array like this (and technically, it is sequential i think, but so fast it appears all at once):
for (UIBezierPath * path in myArrayOfBezierPaths){
path.lineWidth=3;
[path stroke];
[path release];
}
lastly, how could I make each path a different color?

Answer 1

You need to redraw the view multiple times, each time drawing more of your paths. To accomplish this, you need use a timer of some kind and have a way to keep track of which paths you're drawing.
To keep track of the paths you could use an NSInteger instance variable and increment it each time another path is drawn, then in -drawRect: check the value of that variable and draw the appropriate number of paths.
Then you would implement a method that updates the ivar and redraws the view. Here is a very simplistic version:
//assume pathsToDraw is an NSInteger ivar
//and that myArrayOfBezierPaths is an NSArray ivar
//containing UIBezierPath objects
- (void)startDrawingPaths
{
//draw the first path
pathsToDraw = 1;
[view setNeedsDisplay];
//schedule redraws once per second
[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(updateView:) userInfo:nil repeats:YES];
}
- (void)updateView:(NSTimer*)timer
{
//increment the path counter
pathsDrawn++;
//tell the view to update
[view setNeedsDisplay];
//if we've drawn all our paths, stop the timer
if(pathsDrawn >= [myArrayOfBezierPaths count])
{
[timer invalidate];
}
}
Your drawing method would look something like this:
- (void)drawRect:(CGRect)rect
{
NSInteger i = 0;
for (i = 0; i < pathsDrawn; i++)
{
UIBezierPath * path = [myArrayOfBezierPaths objectAtIndex:i];
path.lineWidth=3;
[path stroke];
}
}
As far as color goes, you're creating the paths, so you can make them whatever color you like.