Ggtcf

I've subclassed UIPageControl in order to have its current dot bigger.

class CustomPageControl: UIPageControl 
 override var currentPage: Int 
 didSet 
 updateDots()
 
 

 func updateDots() 
 let currentDot = subviews[currentPage]
 let largeScaling = CGAffineTransform(scaleX: 3, y: 3)

 subviews.forEach 
 // apply the large scale of newly selected dot
 // restore the normal scale of previously selected dot
 $0.transform = $0 == currentDot ? largeScaling : .identity
 
 

But the result of the transform isn't centered (the red dot should be aligned with the others):

I've tried (on iOS 12):

• changing the frame or center of currentDot has no effect.


• changing the transform to include a translatedBy(x: CGFloat, y: CGFloat) has no effect.


• 
  

  changing the constraints like here is making the first dot jumping:

  
  
  

  currentDot.translatesAutoresizingMaskIntoConstraints = false
  currentDot.centerYAnchor.constraint(equalTo: self.centerYAnchor, constant: 0)
  currentDot.centerXAnchor.constraint(equalTo: self.centerXAnchor, constant: 0)
  

  
  
  

  

  
  

I got it finally working by rewriting all the subviews constraints by myself.

// https://stackoverflow.com/a/55063316/1033581
class DefaultPageControl: UIPageControl 

 override var currentPage: Int 
 didSet 
 updateDots()
 
 

 private func updateDots() 
 let currentDot = subviews[currentPage]
 let largeScaling = CGAffineTransform(scaleX: 3.0, y: 3.0)
 let smallScaling = CGAffineTransform(scaleX: 1.0, y: 1.0)

 subviews.forEach 
 // Apply the large scale of newly selected dot.
 // Restore the small scale of previously selected dot.
 $0.transform = $0 == currentDot ? largeScaling : smallScaling
 
 

 override func updateConstraints() 
 super.updateConstraints()
 // We rewrite all the constraints
 rewriteConstraints()
 

 private func rewriteConstraints() 
 let systemDotSize: CGFloat = 7.0
 let systemDotDistance: CGFloat = 16.0

 let halfCount = CGFloat(subviews.count) / 2
 subviews.enumerated().forEach 
 let dot = $0.element
 dot.translatesAutoresizingMaskIntoConstraints = false
 NSLayoutConstraint.deactivate(dot.constraints)
 NSLayoutConstraint.activate([
 dot.widthAnchor.constraint(equalToConstant: systemDotSize),
 dot.heightAnchor.constraint(equalToConstant: systemDotSize),
 dot.centerYAnchor.constraint(equalTo: centerYAnchor, constant: 0),
 dot.centerXAnchor.constraint(equalTo: centerXAnchor, constant: systemDotDistance * (CGFloat($0.offset) - halfCount))
 ])
 
 

System constants in the code (7.0 and 16.0) are respectively the size and the distance found for a default UIPageControl dot on iOS 12.