SOLVED: UIScrollView does not really scroll

@jmgawecki

Feb '21

Hi guys,

As above, my scrollview does not scroll, here is my code:

 private func layoutScrollView() {
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(scrollView)
        scrollView.backgroundColor = .systemRed

        NSLayoutConstraint.activate([
            scrollView.topAnchor.constraint             (equalTo: view.topAnchor),
            scrollView.bottomAnchor.constraint          (equalTo: view.bottomAnchor),
            scrollView.leadingAnchor.constraint         (equalTo: view.leadingAnchor),
            scrollView.trailingAnchor.constraint        (equalTo: view.trailingAnchor),
        ])
    }

    private func layoutUIInScrollView() {
        scrollView.addSubview(hiNameLabel)
        scrollView.addSubview(logOutButton)

        NSLayoutConstraint.activate([
            logOutButton.centerXAnchor.constraint       (equalTo: scrollView.centerXAnchor),
            logOutButton.topAnchor.constraint           (equalTo: scrollView.centerYAnchor),
            logOutButton.widthAnchor.constraint         (equalToConstant: 150),
            logOutButton.heightAnchor.constraint        (equalToConstant: 500),

            hiNameLabel.centerXAnchor.constraint        (equalTo: scrollView.centerXAnchor),
            hiNameLabel.topAnchor.constraint            (equalTo: logOutButton.bottomAnchor),
            hiNameLabel.widthAnchor.constraint          (equalToConstant: 150),
            hiNameLabel.heightAnchor.constraint         (equalToConstant: 500),
        ])
    }

Do I miss any particular element? isScrollEnabled = true does not help as I believe its a default.

@jmgawecki

Feb '21

Okay I got it.

A scrollView needs to be pinned to the edges of a view.
Create a contentView = UIView()
Pin a contentView to the edgees of a scrollView
Add two extra constraints for a contentView
1. contentView's width to scrollView's width
2. contentView's height to fixed to the value that you calculated

 private func layoutScrollViewAndContentView() {
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        contentView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(scrollView)
        scrollView.addSubview(contentView)
        scrollView.backgroundColor = .systemRed
        NSLayoutConstraint.activate([
            scrollView.topAnchor.constraint             (equalTo: view.topAnchor),
            scrollView.bottomAnchor.constraint          (equalTo: view.bottomAnchor),
            scrollView.leadingAnchor.constraint         (equalTo: view.leadingAnchor),
            scrollView.trailingAnchor.constraint        (equalTo: view.trailingAnchor),

            contentView.topAnchor.constraint            (equalTo: scrollView.topAnchor),
            contentView.bottomAnchor.constraint         (equalTo: scrollView.bottomAnchor),
            contentView.leadingAnchor.constraint        (equalTo: scrollView.leadingAnchor),
            contentView.trailingAnchor.constraint       (equalTo: scrollView.trailingAnchor),

            contentView.widthAnchor.constraint          (equalTo: scrollView.widthAnchor),
            contentView.heightAnchor.constraint         (equalToConstant: 2000),

        ])
    }

    private func layoutUIInScrollView() {
        contentView.addSubview(hiNameLabel)
        contentView.addSubview(logOutButton)

        NSLayoutConstraint.activate([
            hiNameLabel.centerXAnchor.constraint        (equalTo: contentView.centerXAnchor),
            hiNameLabel.topAnchor.constraint            (equalTo: contentView.topAnchor),
            hiNameLabel.widthAnchor.constraint          (equalToConstant: 150),
            hiNameLabel.heightAnchor.constraint         (equalToConstant: 2000),

            logOutButton.centerXAnchor.constraint       (equalTo: contentView.centerXAnchor),
            logOutButton.topAnchor.constraint           (equalTo: contentView.centerYAnchor),
            logOutButton.widthAnchor.constraint         (equalToConstant: 150),
            logOutButton.heightAnchor.constraint        (equalToConstant: 500),
        ])
    }

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