Rotation gesture produces undesired rotation

Question

I need to rotate an UIImageview on user\'s motion using just one finger motion. For that I use a rotation gesture and then override touchesMoved with this code:

Answer 1

The problem is that you are saying

rotateImageView.transform = CGAffineTransformMakeRotation(angle)

So whatever transform the image view has already (from the previous rotation) is thrown away and completely replaced by a new transform starting at angle. That's the "jump" you are seeing.

What you want to do is apply a rotation transform to the existing transform of the image view. You can do that by calling CGAffineTransformRotate, instead of CGAffineTransformMakeRotation.