Translating a view and the rotating it problem

I have a custom UIImageView, I can drag it around screen by making a translation with (xDif and yDif is the amount fingers moved):

CGAffineTransform translate = CGAffineTransformMakeTranslation(xDif, yDif);
[self setTransform: CGAffineTransformConcat([self transform], translate)]; 

Let's say I moved the ImageView for 50px in both x and y directions. I then try to rotate the ImageView (via gesture recognizer) with:

CGAffineTransform transform = CGAffineTransformMakeRotation([recognizer rotation]);
myImageView.transform = transform;

What happens is the ImageView suddenly moves to where the ImageView was originally located (before the translation - not from the moved position + 50px in both directions).

(It seems that no matter how I translate the view, the self.center of the ImageView subclass stays the same - where it was originally laid in IB).

Another problem is, if I rotate the ImageView by 30 deg, and then try to rotate it a bit开发者_StackOverflow more, it will again start from the original position (angle = 0) and go from there, why wouldn't it start from the angle 30 deg and not 0.

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You are overwriting the earlier transform. To add to the current transform, you should do this –

myImageView.transform = CGAffineTransformRotate(myImageView.transform, recognizer.rotation);

Since you're changing the transform property in a serial order, you should use CGAffineTransformRotate, CGAffineTransformTranslate and CGAffineTransformScale instead so that you add to the original transform and not create a new one.