import UIKit

class ViewController: UIViewController {

    //
    let scrollView: UIScrollView = {
        
        let sv = UIScrollView()
        sv.translatesAutoresizingMaskIntoConstraints = false
        return sv
    }()
    
    let lipsumLbl: UILabel = { // you can use here any of your subview
        
        let lbl = UILabel()
        lbl.translatesAutoresizingMaskIntoConstraints = false
        lbl.text = """
        Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce eleifend nisi sit amet mi aliquet, ut efficitur risus pellentesque. Phasellus nulla justo, scelerisque ut libero id, aliquet ullamcorper lectus. Integer id iaculis nibh. Duis feugiat mi vitae magna tincidunt, vitae consequat dui tempor. Donec blandit urna nec urna volutpat, sit amet sagittis massa fringilla. Pellentesque luctus erat nec dui luctus, sed maximus urna fermentum. Nullam purus nibh, cursus vel ex nec, pulvinar lobortis leo. Proin ac libero rhoncus, bibendum lorem sed, congue sapien. Donec commodo, est non mollis malesuada, nisi massa tempus ipsum, a varius quam lorem vitae nunc.
        
        Cras scelerisque nisi dolor, in gravida ex ornare a. Interdum et malesuada fames ac ante ipsum primis in faucibus. Maecenas vitae nisl id erat sollicitudin accumsan sit amet viverra sapien. Etiam scelerisque vulputate ante. Donec magna nibh, pharetra sed pretium ac, feugiat sit amet mi. Vestibulum in ipsum vitae dui vehicula pulvinar eget ut lectus. Fusce sagittis a elit ac elementum. Fusce iaculis nunc odio, at fermentum dolor varius et. Suspendisse consectetur congue massa non gravida. Sed id elit vitae nulla aliquam euismod. Pellentesque accumsan risus dolor, eu cursus nibh semper id.
        
        Vestibulum vel tortor tellus. Suspendisse potenti. Pellentesque id sapien eu augue placerat dictum. Fusce tempus ligula at diam lacinia congue in ut metus. Maecenas volutpat tellus in tellus maximus imperdiet. Integer dignissim condimentum lorem, id luctus nisi maximus at. Nulla pretium, est sit amet mollis eleifend, tellus nulla viverra dolor, ac feugiat massa risus a lectus. Pellentesque ut pulvinar urna, blandit gravida ipsum. Nullam volutpat arcu nec fringilla auctor. Integer egestas enim commodo, faucibus neque ac, rutrum magna. Vivamus tincidunt rutrum auctor. Cras at rutrum felis. Fusce elementum lorem ut pharetra venenatis.
        """
        lbl.textColor = .darkGray
        lbl.font = UIFont.systemFont(ofSize: 16)
        lbl.numberOfLines = 0
        return lbl
    }()
    
    //======================================================================//
    //
    // MARK:- viewDidLoad
    //
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setupViews()
        setupAutoLayout()
    }
    
    func setupViews() {
        
        title = "ScrollView Demo"
        view.backgroundColor = .white
        view.addSubview(scrollView)
        scrollView.addSubview(lipsumLbl)
    }
    
    func setupAutoLayout() {
        
        scrollView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        scrollView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        scrollView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        
        lipsumLbl.topAnchor.constraint(equalTo: scrollView.topAnchor).isActive = true
        lipsumLbl.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        lipsumLbl.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        lipsumLbl.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor).isActive = true
    }
}

输出:

对于任何视图，框架及其内容的大小是相同的，即如果你有一些内容(例如图像)的大小为200 * 800，那么它的框架也是200 * 800。

这对于scrollview的内容是不正确的。内容通常大于scrollView的帧大小。如果内容宽度相同，则只能垂直滚动。如果高度相同，则只能水平滚动。因此它是唯一需要6个约束而不是4个约束的视图。对于任何其他具有超过4个必要约束的视图都将导致冲突。

要设置你的滚动视图，它的内容和滚动的位置，你基本上需要回答三个问题:

我的身材有多大?即在任何给定时刻滚动视图应该有多大?2 .拓展例句我只想用屏幕一半的高度，所以

scrollview.frame = (x: 0, y:0, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height / 2)

How much scrolling space do I need? ie How big is the content? e.g. the frame can be just 500 points of width, but then you can set an image with 7000 points, which would take quite some time to scroll horizontally. Or let it be exactly 500 points of width which then means no horizontal scrolling can happen. How much have you scrolled at the moment? Say your content's (or image) width was 7000 and the frame size is just 500. To get to the end of the image, you'd need to scroll 6500 points to the right. The 3rd part really doesn't affect the constraints. You can ignore that for now. Understanding it just helps how a scrollView works.

解决方案

基本上，如果你忽略了2个额外的约束(关于内容大小)，那么布局引擎将会因为模糊性而抱怨。它不知道内容的哪些区域被隐藏(在scrollView中不可见)，哪些区域的内容不被隐藏(在scrollView中可见)。

所以一定要为内容添加大小限制。要了解更多，请看这个答案

但有时我不添加大小限制到我的视图，它只是工作。为什么呢?

If all the contents you've added into the scrollview are constrained to the edges of the scrollview, then as the content grow the scrollview will add space to accommodate. It's just that you might be using UIViews where its intrinsicContentSize is 0 so the scrollView will still complain about ambiguity of its content. However if you've used a UILabel and it has a non-empty text, then its intrinsicContentSize is set (based on Font size and text length and line breaks, etc) so the scrollView won't complain about its ambiguity.

我在youTube上做了一个视频 在Xcode中只使用Storyboard滚动StackViews

我认为这里会出现两种情况。

scrollView -内的视图

没有任何内在内容大小(例如UIView) 大小(例如UIStackView)

对于这两种情况下的垂直可滚动视图，您需要添加以下约束:

4个从上，左，下，右的约束。 与scrollview宽度相等(用于停止水平滚动)

对于具有自身固有内容高度的视图，您不需要任何其他约束。

对于没有任何内在内容高度的视图，需要添加高度约束。只有当高度限制大于scrollView的高度时，视图才会滚动。

我想这是10秒后的作品。我在XCode 7.3中观察到它，并制作了一个视频。检查:

https://www.youtube.com/watch?v=yETZKqdaPiI

你所要做的就是给UIScrollView添加一个宽度和高度相同的子视图。然后选择ViewController并按下Reset到建议的约束。为了更清楚地理解，请查看视频。

谢谢

使用自动布局

在一个定义良好的视图中添加滚动视图，然后在滚动视图中添加堆栈视图

从滚动视图和堆栈视图中添加上、左、右、下、中心X和中心Y约束到相关的超级视图中

确保约束从堆栈视图链接到正确的父视图(scrollview)，因为当前默认设置是添加Align Top约束，而不是Top Space约束。

Swift 4+方法:

1)设置UIScrollView的上、下、左、右边缘为0

2)在UIScrollView中添加一个UIView，并设置顶部、底部、前边距和尾随边距为0(等于UIScrollView的边距)。

3)最重要的部分是设置宽度和高度，其中高度约束的优先级应该低。

private func setupConstraints() {

    // Constraints for scrollView
    scrollView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
    scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
    scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
    scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true

    // Constraints for containerView
    containerView.topAnchor.constraint(equalTo: scrollView.topAnchor).isActive = true
    containerView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor).isActive = true
    containerView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor).isActive = true
    containerView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor).isActive = true
    containerView.widthAnchor.constraint(equalTo: scrollView.widthAnchor).isActive = true

    let heightConstraint = containerView.heightAnchor.constraint(equalTo: scrollView.heightAnchor)
    heightConstraint.priority = UILayoutPriority(rawValue: 250)
    heightConstraint.isActive = true
}