Polygon drawn with CG gets distorted after a UIView animation.

Question

Hi all,
I've managed to draw a polygon on an UIView with a helper function that gives me an array of CGPoints which I loop through going CGContextAddLineToPoint.
I can rotate the polygon by applying a CAAffineTransformMakeRotation object, I have a UIButton associated with a rotate function and it works fine.
Problem is if I move the UIView down (as with a UIView beginAnimations) and the polygon is rotated in any manner, I can see an animation of it being distorted and disappearing!
Any clues???

Answer 1

G'day mate! My favorite San Fran radio station is currently running a 60 sec. travel commercial featuring an authentic Aus announcer (or crocodile hunter) along with an American translator. The idea is to teach us to speak Australian before we get there. I'm a slow learner, but maybe by the time I learn Obj-C I'll know how to ask for directions to Queensland.
No, I've never been a student at Stanford. CS 193P, last autumn, was given through the Stanford Center for Professional Development, so you didn't need to be a regular Stanford student; an application to the graduate school was required, but all the lectures were on video and I don't think you ever needed to be on campus to complete the course. I think the full tuition was over $3000. I would have gone for that if it had been a live class with the opportunity to ask questions. But I was told questions could only be asked by e-mail and those might or might not be answered in the recorded lectures. I didn't even ask my employer to pay for the class since my job was to develop Win32 apps. At the time I wasn't willing to confide a secret desire to become an iPhone programmer.
Anyway.. (I can't wait to see the comments about people who litter this forum with their life story) I haven't yet built a test bed to try out your code, but you are indeed moving your subview by resetting the frame. Note the warning in the doc: "If the transform property is not the identity transform, the value of this property is undefined" [https://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIVie wClass/UIView/UIView.html#//appleref/doc/uid/TP40006816-CH3-SW5].
Try adding a translation to the current transform like this:
CGAffineTransform t1 = myPolyView.transform;
CGAffineTransform t2 = CGAffineTransformMakeTranslation(x, y);
myPolyView.transform = CGAffineTransformConcat(t1, t2);