stumped stumped - 7 months ago 83
Swift Question

Incorrect position of anchor point in CGPointApplyAffineTransform (iOS/Swift)

It seems that the

anchor point
of my
buttonView
is changing based on the position of
view
. I want the
buttonView
to shrink to the middle of itself rather than the middle of
view
. I was wondering what I'm doing wrong? Or if I'm completely misunderstanding anchor points? I tried reading some articles but they seemed to suggest that the anchor point of an object referred to its own coordinates rather than its super view's.

import UIKit

class ViewController: UIViewController {
var buttonView:UIView!
var toggleButton:UIButton!
var isVisible = false

override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.

let buttonTitles = ["1", "2", "3"]
let size:CGFloat = 100.0

let viewSize = CGFloat(buttonTitles.count) * size
buttonView = UIView(frame: CGRectMake(40, 40, viewSize, viewSize))

setAnchorPoint(CGPointMake(0.5, 0), forView: buttonView)
buttonView.layer.anchorPoint = CGPointMake(0.5, 0.0)
view.addSubview(buttonView)

for (index, title) in buttonTitles.enumerate() {
let button = UIButton(type: .Custom) as UIButton
button.frame = CGRectMake(0, size * CGFloat(index), size, size)
button.setTitle(title, forState: .Normal)
button.backgroundColor = UIColor.redColor()
buttonView.addSubview(button)
}

toggleButton = UIButton(type: .Custom) as UIButton
toggleButton.frame = CGRectMake(200, 100, 80, 50)
toggleButton.setTitle("Toggle", forState: .Normal)
toggleButton.backgroundColor = UIColor.purpleColor()
toggleButton.addTarget(self, action: #selector(ViewController.animate), forControlEvents: .TouchUpInside)
view.addSubview(toggleButton)
}

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
}

func animate() {

if (isVisible) { // collapse it
isVisible = false

UIView.animateWithDuration(0.5, animations: {
self.buttonView.transform = CGAffineTransformMakeScale(0.2, 0.2)
})
}

else { // expand it
isVisible = true

UIView.animateWithDuration(0.5, animations: {
self.buttonView.transform = CGAffineTransformMakeScale(1.0, 1.0)
})
}
}
}


Before clicking Toggle: enter image description here

After clicking Toggle: enter image description here

Answer

Nevermind, turns out I just set my buttonView's width too big.