How to programmatically rotate the view by 180 deg

问题:

How to programmatically rotate the view by 180 degrees in my iPhone App?

回答1:

Should be possible by using CGAffineTransform

Quote from this question, this should do the trick:

CGFloat radians = atan2f(yourView.transform.b, yourView.transform.a);
CGFloat degrees = radians * (180 / M_PI);
CGAffineTransform transform = CGAffineTransformMakeRotation((90 + degrees) * M_PI/180);
yourView.transform = transform;

回答2:

As ’CGAffineTransformRotate’ uses radians as its unit of measure, and 180 degrees is the same as PI, instead of the math provided in other answers you can simply do:

view.transform = CGAffineTransformRotate(view.transform, M_PI);

Swift 3:

view.transform = view.transform.rotated(by: .pi)

If you plan on doing a lot of transforms, it's probably best to read up on radians, so you understand what is going on.

回答3:

Simple solution:

view.transform = CGAffineTransformMakeRotation(degrees*M_PI/180);

回答4:

Same outcome as @Manny's answer using a different function.

 CGFloat degreesOfRotation = 180.0;
 view.transform = CGAffineTransformRotate(view.transform,
     degreesOfRotation * M_PI/180.0);

回答5:

In Swift 3 :

let rotationDegrees =  180.0
let rotationAngle = CGFloat(rotationDegrees * M_PI / 180.0)
view.transform = CGAffineTransform(rotationAngle: rotationAngle)

回答6:

Swift 4:

self.view.transform = CGAffineTransform(rotationAngle: .pi);

And a COMMENT (I evidently don't have enough points to enter my comment on his/her answer) for Benjamin Mayo or vtcajones answer of:

view.transform = view.transform.rotated(by: .pi)

This will work the first time, but the next time it is called it will rotate the view again, back to the original rotation, which is probably not what you want. It would be safer to set the transform value exactly each time.

回答7:

Latest Swift 3 syntax:

view.transform = view.transform.rotated(by: .pi)