CODEWITHSUNDEEP
iosswiftiphone
user12974833
user12974833

Reputation:

Swift - Make whole view controller vertically scrollable: have empty space at bottom safe area

I have a MainViewController with some elements inside. I want the whole view to be vertically scrollable. I made this BaseScrollableViewController class:

class BaseScrollableViewController: UIViewController, UIScrollViewDelegate {

    lazy var scrollView: UIScrollView = {
        let scrollView = UIScrollView()
        scrollView.delegate = self
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.showsHorizontalScrollIndicator = false
        scrollView.showsVerticalScrollIndicator = false
        return scrollView
    }()

    lazy var contentView: UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
    
        view.addSubview(scrollView)
        scrollView.addSubview(contentView)
    
        NSLayoutConstraint.activate([
            scrollView.topAnchor.constraint(equalTo: view.topAnchor),
            scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        
            contentView.topAnchor.constraint(equalTo: scrollView.topAnchor),
            contentView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),
            contentView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),
            contentView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor),
            contentView.widthAnchor.constraint(equalTo: scrollView.widthAnchor),
            contentView.heightAnchor.constraint(equalTo: scrollView.heightAnchor)
        ])
    }
}

Then I made the MainViewController a subclass of this BaseScrollableViewController. Inside, I use contentView to add all the subviews.

Now it scrolls vertically. However, when I scroll down to the bottom, here is what is shows:

Screenshot

Note that there is an empty space at the bottom.

I have tried the scrollView.contentInsetAdjustmentBehavior = .never, but then the scrollView becomes not scrollable.

So how can I fix this? Thanks!

Upvotes: 0

Views: 372

Answers (1)

Claudio
Claudio

Reputation: 5183

For a scrollView to be scrollable, its subviews need to be bigger than the scrollView. By specifying the following constraint contentView.heightAnchor.constraint(equalTo: scrollView.heightAnchor) on the BaseScrollableViewController you are specifying that the contentView will have the same height of the scrollView, thus making the view not scrollable when setting scrollView.contentInsetAdjustmentBehavior = .never.

You can test this by adding a multiplier value on the contentView height constraint:

contentView.heightAnchor.constraint(equalTo: scrollView.heightAnchor, multiplier: 1.5)

And enabling

`scrollView.contentInsetAdjustmentBehavior = .never`

Upvotes: 1

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