On Jul 18, 2014, at 4:51 AM, 2551 <[email protected]> wrote:
> I have a problem which I can't find anyone else asking after hours of
> searches through stackexchange and the like.
>
> In a UIView, I'm rotating a subview with a Gesture recognizer that calls this
> selector:
>
> - (IBAction)rotateShape:(UIRotationGestureRecognizer *)gesture {
> gesture.view.transform = CGAffineTransformMakeRotation(gesture.rotation);
> }
>
> The rotation performs as expected and all is right with the world. However,
> as soon as I attempt to touch or move the rotated subview again (it also has
> a pan gesture), it reverts to its original orientation.
No, when you apply a transform to a view, it becomes _the_ transform; it isn't
retaining previous translation state. Based on what you've said, it sounds like
when you touch/move the object that you're applying a translation transform to
the view.
> It seems the original transform values are still being retained and held by
> the object or by the drawing context (I'm still not quite comfortable with
> all the graphics theory; indeed, this is my first attempt at trying to unlock
> its mysteries).
You may already know this but the CFAffineTransformMake*() functions apply a
single operation (rotate, scale or translate) to the identity transform. If,
for example, you called CGAffineTransformMakeRotation() and then later
CGAffineTransformMakeTranslation(), then the rotation will be lost.
> What else do I need to do to ensure the new rotated, orientation "sticks" so
> that I can move the shape without it reverting to the original orientation?
Keep track of translation and rotation values in your model and then build
translated+rotated transforms that reflect the current state of each object.
- (IBAction)rotateShape:(UIRotationGestureRecognizer *)gesture {
modelObject = ...;
modelObject.rotation = gesture.rotation;
gesture.view.transform = [self transformForModelObject:modelObject];
}
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