Rotate UIView around its center keeping its size

Question

I\'m trying to rotate an UIView a few radians but after applying the transformation it doesn\'t look to be keeping its size. What\'s the proper way to achieve t

Answer 1

The CGAffineTransformRotate transformation rotates from an existing affine transform. The fact that you are using CGAffineTransformIdentity might be the issue. You must specify the current transform of your view.

#define DEGREES_TO_RADIANS(angle) ((angle) / 180.0 * M_PI)
...
double rads = DEGREES_TO_RADIANS(240);
CGAffineTransform transform = CGAffineTransformRotate(self.arrowView.transform, rads);
self.arrowView.transform = transform;

Also, you might want to consider:

self.arrowView.transform = CGAffineTransformMakeRotation(rads);

EDIT : If you can, share what you kind of transformation (animated/inanimate , single/iterative) you want to achieve. I believe there might be a better, optimized way of doing this.

Answer 2

Swift + extension are your friends!

// MARK: - UIView Extension -

extension UIView {

    /**
     Rotate a view by specified degrees

     - parameter angle: angle in degrees
     */
    func rotate(angle: CGFloat) {
        let radians = angle / 180.0 * CGFloat.pi
        let rotation = CGAffineTransformRotate(self.transform, radians);
        self.transform = rotation
    }

}

In this way, anywhere in your code:

let view = UIView(frame: CGRectMake(0, 0, 100, 100))
view.backgroundColor = UIcolor.redColor()
view.rotate(angle: 90)

Answer 3

Update Luca Davanzo's answer with Swift 4:

/**
 Rotate a view by specified degrees

 - parameter angle: angle in degrees
 */
func rotate(angle: CGFloat) {
    let radians = angle / 180.0 * CGFloat.pi
    let rotation = self.transform.rotated(by: radians)
    self.transform = rotation
}

Answer 4

On Swift 3:

let degrees: CGFloat = -90
let radians = CGFloat(__sinpi(degrees.native/180.0))
view.transform = CGAffineTransform(rotationAngle: radians)

I'm using -90 because of this specific part of the documentation about the rotationAngle you have to pass to CGAffineTransform:

The angle, in radians, by which this matrix rotates the coordinate system axes. In iOS, a positive value specifies counterclockwise rotation and a negative value specifies clockwise rotation.

Answer 5

To my mind you need to calculate the center of your triangle and rotate around this point. Now you rotate the arrow around the center of your square.

See: One step affine transform for rotation around a point?

I Hope it will help you.

Answer 6

I avoid using macros unless necessary. This works perfectly well

float degrees = 20; //the value in degrees
view.transform = CGAffineTransformMakeRotation(degrees * M_PI/180);