How to add UIImageViews to a UIStackView that is constrained to the centerXAnchor of a view? - uiimageview

Question

I'm trying to add profile icons via UIImageViews to a UIStackView in order to keep the icons centered in a view. How would I go about adding UIImageViews of a fixed frame to a UIStackView and keep the UIStackView centered in the main view according to varying numbers of UIImageViews in the UIStackView?
let memberIcons: UIStackView = {
let iconView = UIStackView()
iconView.translatesAutoresizingMaskIntoConstraints = false
iconView.axis = .horizontal
iconView.spacing = 5
iconView.distribution = .equalSpacing
iconView.alignment = .center
return iconView
}()
for member in story!.members {
let circle = UIImageView()
circle.frame = CGRect(x: 0, y: 0, width: 36, height: 36)
circle.translatesAutoresizingMaskIntoConstraints = false
circle.layer.cornerRadius = CGFloat(circle.frame.width / 2)
circle.image = member.profilePicture
circle.contentMode = .scaleAspectFill
circle.clipsToBounds = true
memberIcons.addArrangedSubview(circle)
}

Answer 1

Because you set memberIcons.distribution = .equalSpace, the stack view will ask its subviews for their intrinsic sizes. When asked, the UIImage (i.e. circle) will calculate its intrinsic size as "image pixel size / scale", which is not what you want -- you want the image to be of fixed size (36 x 36).
Use Auto Layout on circle:
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(memberIcons)
memberIcons.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
memberIcons.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
// Limit the stack view's width to no more than 75% of the superview's width
// Adjust as needed
memberIcons.widthAnchor.constraint(lessThanOrEqualTo: view.widthAnchor, multiplier: 0.75).isActive = true
let width: CGFloat = 36.0
for member in story!.members {
// We don't care about the frame here as we're gonna use auto layout
let circle = UIImageView(frame: .zero)
circle.translatesAutoresizingMaskIntoConstraints = false
circle.layer.cornerRadius = width / 2
circle.image = member.profilePicture
circle.contentMode = .scaleAspectFill
circle.clipsToBounds = true
circle.layer.borderWidth = 1
circle.layer.borderColor = UIColor.lightGray.cgColor
memberIcons.addArrangedSubview(circle)
circle.widthAnchor.constraint(equalToConstant: width).isActive = true
circle.heightAnchor.constraint(equalToConstant: width).isActive = true
}
}
Result:
Because we limit the width of the UIStackView, there a maximum number of profile images you can add (7 in this case) before you get a bunch of auto layout error on the console. You can enclose the Stack View inside a Scroll View or use a Collection View for a matrix-like display.