Changing my CALayer's anchorPoint moves the view

I had the same problem. Brad Larson's solution worked great even when the view is rotated. Here is his solution translated into code.

-(void)setAnchorPoint:(CGPoint)anchorPoint forView:(UIView *)view
{
    CGPoint newPoint = CGPointMake(view.bounds.size.width * anchorPoint.x, 
                                   view.bounds.size.height * anchorPoint.y);
    CGPoint oldPoint = CGPointMake(view.bounds.size.width * view.layer.anchorPoint.x, 
                                   view.bounds.size.height * view.layer.anchorPoint.y);

    newPoint = CGPointApplyAffineTransform(newPoint, view.transform);
    oldPoint = CGPointApplyAffineTransform(oldPoint, view.transform);

    CGPoint position = view.layer.position;

    position.x -= oldPoint.x;
    position.x += newPoint.x;

    position.y -= oldPoint.y;
    position.y += newPoint.y;

    view.layer.position = position;
    view.layer.anchorPoint = anchorPoint;
}

And the swift equivalent:

func setAnchorPoint(anchorPoint: CGPoint, forView view: UIView) {
    var newPoint = CGPointMake(view.bounds.size.width * anchorPoint.x, view.bounds.size.height * anchorPoint.y)
    var oldPoint = CGPointMake(view.bounds.size.width * view.layer.anchorPoint.x, view.bounds.size.height * view.layer.anchorPoint.y)

    newPoint = CGPointApplyAffineTransform(newPoint, view.transform)
    oldPoint = CGPointApplyAffineTransform(oldPoint, view.transform)

    var position = view.layer.position
    position.x -= oldPoint.x
    position.x += newPoint.x

    position.y -= oldPoint.y
    position.y += newPoint.y

    view.layer.position = position
    view.layer.anchorPoint = anchorPoint
}

SWIFT 4.x

func setAnchorPoint(anchorPoint: CGPoint, forView view: UIView) {
    var newPoint = CGPoint(x: view.bounds.size.width * anchorPoint.x,
                           y: view.bounds.size.height * anchorPoint.y)


    var oldPoint = CGPoint(x: view.bounds.size.width * view.layer.anchorPoint.x,
                           y: view.bounds.size.height * view.layer.anchorPoint.y)

    newPoint = newPoint.applying(view.transform)
    oldPoint = oldPoint.applying(view.transform)

    var position = view.layer.position
    position.x -= oldPoint.x
    position.x += newPoint.x

    position.y -= oldPoint.y
    position.y += newPoint.y

    view.layer.position = position
    view.layer.anchorPoint = anchorPoint
}

The Layer Geometry and Transforms section of the Core Animation Programming Guide explains the relationship between a CALayer's position and anchorPoint properties. Basically, the position of a layer is specified in terms of the location of the layer's anchorPoint. By default, a layer's anchorPoint is (0.5, 0.5), which lies at the center of the layer. When you set the position of the layer, you are then setting the location of the center of the layer in its superlayer's coordinate system.

Because the position is relative to the anchorPoint of the layer, changing that anchorPoint while maintaining the same position moves the layer. In order to prevent this movement, you would need to adjust the layer's position to account for the new anchorPoint. One way I've done this is to grab the layer's bounds, multiply the bounds' width and height by the old and new anchorPoint's normalized values, take the difference of the two anchorPoints, and apply that difference to the position of the layer.

You might even be able to account for rotation this way by using CGPointApplyAffineTransform() with your UIView's CGAffineTransform.

The key to solving this was to use the frame property, which is weirdly the only thing that changes.

Swift 2

let oldFrame = self.frame
self.layer.anchorPoint = CGPointMake(1, 1)
self.frame = oldFrame

Swift 3

let oldFrame = self.frame
self.layer.anchorPoint = CGPoint(x: 1, y: 1)
self.frame = oldFrame

Then I do my resize, where it scales from the anchorPoint. Then I have to restore the old anchorPoint;

Swift 2

let oldFrame = self.frame
self.layer.anchorPoint = CGPointMake(0.5,0.5)
self.frame = oldFrame

Swift 3

let oldFrame = self.frame
self.layer.anchorPoint = CGPoint(x: 0.5, y: 0.5)
self.frame = oldFrame

EDIT: this flakes out if the view is rotated, as the frame property is undefined if a CGAffineTransform has been applied.