rotate UI subview (CFAffline Transform)
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.
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). 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?
Thanks for any help.
Phil
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Re: rotate UI subview (CFAffline Transform)
Transforms are meant to be tiered / layered. In other words, if you do another
transform via a pan or rotation, it’s going to reset. If your view was already
scaled (matrix has been edited), doing a Make transform (ex:
CGAffineTransformMakeRotation) would reset it. Transforms manipulate the
layer(s). Your view isn’t aware the layer has been tampered with.
If it isn’t another transform that is resetting the layer, then you need to
reapply your transform. You can can easily get your current transformation via:
CGAffineTransform transformation = theRotatedView.transform;
CGFloat amountRotated = atan2f(transformation.b, transformation.a); // b and a
are the values manipulated for matrix math.
A debugging method that you can use is: NSStringFromCGAffineTransform(), will
help output your current transform. I’m sure you’ll see the matrix numbers
reset.
Regards
- Cody
It would help to see the code that makes the pan gesture.
On Jul 18, 2014, at 4:51 AM, 2551 2551p...@gmail.com 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.
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). 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?
Thanks for any help.
Phil
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Re: rotate UI subview (CFAffline Transform)
On Jul 18, 2014, at 4:51 AM, 2551 2551p...@gmail.com 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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[Solved] rotate UI subview (CFAffline Transform)
Thanks Steve and Cody You were both correct that what was happening was that the subsequent translation was cancelling the rotation. All I needed to do was store the rotation as a CGFloat on the object and then call the rotation again after the move. Thanks again. signature.asc Description: Message signed with OpenPGP using GPGMail ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
