CoreAnimation rotating an object and changing it's position at the same time

Question

What I'm trying to do is to rotate a view left and right and at the same time move it's position up and down.

Here's the code I have:

CGAffineTransform leftWobble = CGAffineTransformRotate(CGAffineTransformIdentity, RADIANS(-12.0));
CGAffineTransform rightWobble = CGAffineTransformRotate(CGAffineTransformIdentity, RADIANS(12.0));

flyingGuy.transform = leftWobble;  // starting point

[UIView beginAnimations:@"wobble" context:flyingGuy];
[UIView setAnimationRepeatAutoreverses:YES];
[UIView setAnimationRepeatCount:1000];
[UIView setAnimationDuration:1.3];
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(wobbleEnded:finished:context:)];

flyingGuy.transform = rightWobble;
CGRect frame = flyingGuy.frame;
frame.origin.y += 10;
[flyingGuy setFrame:frame];

[UIView commitAnimations];


- (void)wobbleEnded:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context  {
    if ([finished boolValue]) {
        UIView* item = (UIView *)context;
        item.transform = CGAffineTransformIdentity;
    }
}

With the current code, the view size changes as it moves up or down. Any suggestions?

Answer 1

Don't set or get the frame after you have set the transform!

From the docs:

Warning If the transform property is not the identity transform, the value of this property is undefined and therefore should be ignored.

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What you should do instead

Change the center property of the view. You are only changing the position anyway and this is safe when you have a transform applied.