How to know the current position of a UIImageView moving? - iphone

Question

I have to do a little game where 2 images are moving horizontally on the same line. I want to know when they are superposed, in order to display a new image instead of 2.
What is the best way to do it ?
Way I was thinking to do :
I need to know the position somewhat during the animation of my UIImageViews and I'll try with timer to refresh the imageView when I discover that the 2 imageViews are close.
I have this function so far to move an Image :
- (void)moveImage:(UIImageView *)image duration:(NSTimeInterval)duration
curve:(int)curve x:(CGFloat)x y:(CGFloat)y
{
// Setup the animation
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:duration];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationBeginsFromCurrentState:YES];
// The transform matrix
CGAffineTransform transform = CGAffineTransformMakeTranslation(x, y);
image.transform = transform;
// Commit the changes
[UIView commitAnimations];
}
Thank you for you help !

Answer 1

I think checking the position multiple times every second is not the best way to do it. If you can, you should precalculate the point in time, when the view overlap!
In any way, you shouldn't use the affinetransform for moving the imageview but just moving the frame of the imageview, by changing the frame or the center property of the view!
If you cant precalculate this, here are some tips on how to implement the timer and checking:
For implementing the timer you can use:
[NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:#selector(checkPosition:) userInfo:nil repeats:YES];
This will call the function every 0.1 seconds.
- (void)checkPosition:(NSTimer *)timer
In this method you could access the imageViews UILayer to find out the actual position of this view by calling
CGFrame currentFrame = [imageView.layer presentationLayer].frame;
To be able to do this you have to import the QuartzCore framework!