UIScrollView not scrolling w/ programmatic autolayout constraints

Question

I am trying to understand how to use a UIScrollView programmatically.

When I give my content a size that does not fit on screen though, it does not scroll.


final class ProfileView: UIView {

    private var isIpad: Bool {
        return UIDevice.current.userInterfaceIdiom == .pad
    }

    private lazy var headerImageView: UIImageView = {
        let iv = UIImageView(frame: .zero)
        iv.translatesAutoresizingMaskIntoConstraints = false
        iv.heightAnchor.constraint(equalToConstant: 600).isActive = true
        iv.backgroundColor = .purple
        return iv
    }()

    private lazy var profileImageView: UIImageView = {
        let iv = UIImageView(frame: .zero)
        iv.translatesAutoresizingMaskIntoConstraints = false
        [iv.heightAnchor, iv.widthAnchor].forEach { $0.constraint(equalToConstant: 170).isActive = true }
        iv.layer.cornerRadius = 170 / 2
        iv.layer.borderColor = .white
        iv.layer.borderWidth = 3
        iv.layer.masksToBounds = true
        iv.contentMode = .scaleAspectFill
        iv.clipsToBounds = true
        iv.backgroundColor = .red

        return iv
    }()

    private(set) lazy var nameLabel: UILabel = {
        let label = UILabel(frame: .zero)
        label.translatesAutoresizingMaskIntoConstraints = false
        label.text = "Foo\nBar"
        label.numberOfLines = 2
        return label
    }()

    private lazy var contentScrollView: UIScrollView = {
        let sv = UIScrollView(frame: .zero)
        sv.translatesAutoresizingMaskIntoConstraints = false
        return sv
    }()

    override init(frame: CGRect) {
        super.init(frame: frame)

        configureLayout()
    }

    required init?(coder: NSCoder) {
        return nil
    }

    private func configureLayout() {

        addSubview(contentScrollView)
        [headerImageView, profileImageView, nameLabel].forEach { contentScrollView.addSubview($0) }

        let compactConstraints = [
            contentScrollView.topAnchor.constraint(equalTo: safeAreaLayoutGuide.topAnchor),
            contentScrollView.leadingAnchor.constraint(equalTo: safeAreaLayoutGuide.leadingAnchor),
            contentScrollView.bottomAnchor.constraint(equalTo: safeAreaLayoutGuide.bottomAnchor),
            contentScrollView.trailingAnchor.constraint(equalTo: safeAreaLayoutGuide.trailingAnchor),

            headerImageView.topAnchor.constraint(equalTo: topAnchor),
            headerImageView.leadingAnchor.constraint(equalTo: leadingAnchor),
            headerImageView.trailingAnchor.constraint(equalTo: trailingAnchor),

            profileImageView.centerYAnchor.constraint(equalTo: headerImageView.bottomAnchor),
            profileImageView.centerXAnchor.constraint(equalTo: centerXAnchor),

            nameLabel.topAnchor.constraint(equalTo: profileImageView.bottomAnchor, constant: 16),
            nameLabel.centerXAnchor.constraint(equalTo: profileImageView.centerXAnchor),

        ]

        NSLayoutConstraint.activate(compactConstraints)
    }
}

This gives me the following -

The header image pushes the name label and avatar off screen and scrolling does not work.

I've read a bunch about giving the scroll view a huge offset so it scrolls, but that surely cannot be correct.

check this out I think it will works for you -> https://stackoverflow.com/questions/44931898/using-scrollview-programmatically-in-swift-3 — emrcftci, Nov 16 '19 at 17:18

Shehata Gamal · Accepted Answer · 2019-11-16T17:37:31.177

You need to create the constraints of all the subviews to the scrollView , add width constraint to the header img = profileview width and finally make bottom of label = bottom of the scrollview to make it infer it's height

let compactConstraints = [

        contentScrollView.topAnchor.constraint(equalTo: safeAreaLayoutGuide.topAnchor),
        contentScrollView.leadingAnchor.constraint(equalTo: safeAreaLayoutGuide.leadingAnchor),
        contentScrollView.bottomAnchor.constraint(equalTo: safeAreaLayoutGuide.bottomAnchor),
        contentScrollView.trailingAnchor.constraint(equalTo: safeAreaLayoutGuide.trailingAnchor),


        headerImageView.topAnchor.constraint(equalTo:contentScrollView.topAnchor),
        headerImageView.leadingAnchor.constraint(equalTo:contentScrollView.leadingAnchor),
        headerImageView.trailingAnchor.constraint(equalTo:contentScrollView.trailingAnchor),  
        headerImageView.widthAnchor.constraint(equalTo: self.widthAnchor) // add this 

        profileImageView.centerYAnchor.constraint(equalTo: headerImageView.bottomAnchor),
        profileImageView.centerXAnchor.constraint(equalTo: centerXAnchor),

        nameLabel.topAnchor.constraint(equalTo: profileImageView.bottomAnchor, constant: 16),
        nameLabel.centerXAnchor.constraint(equalTo: profileImageView.centerXAnchor),
        nameLabel.bottomAnchor.constraint(equalTo: contentScrollView.bottomAnchor)  // and this 
]

I think the `nameLabel.bottomAnchor` should be anchored to `contentScrollView.bottomAnchor` - that aside this is the right answer — nodediggity, Nov 16 '19 at 17:36

UIScrollView not scrolling w/ programmatic autolayout constraints

1 Answers1