ios - 我的带有自动布局约束的 Swift 4 UIScrollView 不滚动

Question

在将 View 添加到我的应用程序之前，我已经创建了一个小型演示 Playground 来让它正常工作。

我有一个 ScrollView ，它将包含许多水平滚动的按钮。我知道这些按钮需要进入 ScrollView 中的容器 View 并创建它。我最初使用自动布局约束来创建所有这些，但现在尝试使用常量来确保内容 View 大于 ScrollView 。但是，按钮仍然不会滚动……我错过了什么吗？ ScrollView 是否不适用于自动布局？

我也在我的 iPad 上以编程方式完成这一切，所以不幸的是，带有界面构建器的解决方案不是一个选项......

完整代码如下:

import UIKit
import PlaygroundSupport

class FilterViewController: UIViewController {
    var filterView: UIView!
    var scrollView: UIScrollView!
    var containerView: UIView!

    override func loadView() {
        filterView = UIView()
        view = filterView
        view.backgroundColor = #colorLiteral(red: 0.909803926944733, green: 0.47843137383461, blue: 0.643137276172638, alpha: 1.0)

        scrollView = UIScrollView()
        scrollView.backgroundColor = #colorLiteral(red: 0.474509805440903, green: 0.839215695858002, blue: 0.976470589637756, alpha: 1.0)
        view.addSubview(scrollView)
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.topAnchor.constraint(equalTo:view.topAnchor, constant:40).isActive = true
        scrollView.leadingAnchor.constraint(equalTo:view.leadingAnchor).isActive = true
        scrollView.widthAnchor.constraint(equalTo:view.widthAnchor).isActive = true
        scrollView.heightAnchor.constraint(equalToConstant: 200).isActive = true
        scrollView.isScrollEnabled = true

        containerView = UIView()
        containerView.backgroundColor = #colorLiteral(red: 0.176470592617989, green: 0.498039215803146, blue: 0.756862759590149, alpha: 1.0)
        scrollView.addSubview(containerView)
        containerView.frame = CGRect(x: 0, y: 0, width: 1080, height: 200)
    }

    class Buttons{
        let button = UIButton()
        init (titleText : String){
            button.backgroundColor = #colorLiteral(red: 0.976470589637756, green: 0.850980401039124, blue: 0.549019634723663, alpha: 1.0)
            button.setTitle(titleText, for: .normal)
            button.frame = CGRect(x: 0, y: 0, width: 200, height: 200)
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        let b1 = Buttons(titleText: "one")
        let b2 = Buttons(titleText: "two")
        let b3 = Buttons(titleText: "three")
        let b4 = Buttons(titleText: "four")
        let b5 = Buttons(titleText: "five")
        let buttonArray = [b1,b2,b3,b4,b5]
        var startPoint : CGFloat = 0.0
        for btn in buttonArray {
            let theBtn = btn.button
            containerView.addSubview(theBtn)
            theBtn.frame = CGRect(x: startPoint, y: 0, width: 200, height: 200)
            startPoint += 220
        }

    }
}

let filterViewController = FilterViewController()
PlaygroundPage.current.liveView = filterViewController

谢谢你!这是具有所有自动布局约束的完整(现在工作)迷你项目:

import UIKit
import PlaygroundSupport

class FilterViewController: UIViewController {
    var filterView: UIView!
    var scrollView: UIScrollView!
    var containerView: UIView!

    override func loadView() {
        filterView = UIView()
        view = filterView
        view.backgroundColor = #colorLiteral(red: 0.909803926944733, green: 0.47843137383461, blue: 0.643137276172638, alpha: 1.0)

        scrollView = UIScrollView()
        scrollView.backgroundColor = #colorLiteral(red: 0.474509805440903, green: 0.839215695858002, blue: 0.976470589637756, alpha: 1.0)
        view.addSubview(scrollView)
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.topAnchor.constraint(equalTo:view.topAnchor, constant:40).isActive = true
        scrollView.leadingAnchor.constraint(equalTo:view.leadingAnchor).isActive = true
        scrollView.widthAnchor.constraint(equalTo:view.widthAnchor).isActive = true
        scrollView.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.25).isActive = true
        scrollView.isScrollEnabled = true

        containerView = UIView()
        containerView.backgroundColor = #colorLiteral(red: 0.176470592617989, green: 0.498039215803146, blue: 0.756862759590149, alpha: 1.0)
        scrollView.addSubview(containerView)
        containerView.translatesAutoresizingMaskIntoConstraints = false
        containerView.topAnchor.constraint(equalTo:scrollView.topAnchor).isActive = true
        containerView.leadingAnchor.constraint(equalTo:scrollView.leadingAnchor).isActive = true
        containerView.trailingAnchor.constraint(equalTo:scrollView.trailingAnchor).isActive = true
        containerView.bottomAnchor.constraint(equalTo:scrollView.bottomAnchor).isActive = true
        containerView.heightAnchor.constraint(equalTo: scrollView.heightAnchor).isActive = true



    }

    class Buttons{
        let button = UIButton()
        init (titleText : String){
            button.backgroundColor = #colorLiteral(red: 0.976470589637756, green: 0.850980401039124, blue: 0.549019634723663, alpha: 1.0)
            button.setTitle(titleText, for: .normal)
            //button.frame = CGRect(x: 0, y: 0, width: 200, height: 200)
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        let b1 = Buttons(titleText: "one")
        let b2 = Buttons(titleText: "two")
        let b3 = Buttons(titleText: "three")
        let b4 = Buttons(titleText: "four")
        let b5 = Buttons(titleText: "five")
        let buttonArray = [b1,b2,b3,b4,b5]
        var startPoint = containerView.leadingAnchor
        for btn in buttonArray {
            let theBtn = btn.button
            containerView.addSubview(theBtn)
            theBtn.translatesAutoresizingMaskIntoConstraints = false
            theBtn.leadingAnchor.constraint(equalTo:startPoint, constant:20).isActive = true
            theBtn.topAnchor.constraint(equalTo:containerView.topAnchor).isActive = true
            theBtn.bottomAnchor.constraint(equalTo:containerView.bottomAnchor).isActive = true
            theBtn.widthAnchor.constraint(equalTo: theBtn.heightAnchor).isActive = true
            startPoint = theBtn.trailingAnchor
            containerView.widthAnchor.constraint(equalTo: theBtn.widthAnchor, multiplier:CGFloat(buttonArray.count), constant: CGFloat(buttonArray.count * 20)).isActive = true
        }
    }
}

let filterViewController = FilterViewController()
PlaygroundPage.current.liveView = filterViewController

Answer 1

您可以使用自动布局 来做到这一点。 secret 是将 containerView 的边缘限制到 scrollView 的边缘。这不直观，但是限制 containerView 的边缘并没有设置大小，它只是确保 scrollView 的内容大小随着 containerView 的增长而增长 增长。通过将 containerView 的宽度约束设置为比 scrollView 的宽度更大的常数，内容将水平滚动。

注意当以这种方式配置一个scrollView时，您没有设置scrollView的contentSize。 contentSize 将由 Auto Layout 为您计算，它将等于 containerView 的大小。务必确保 containerView 的大小完全由约束指定。

以下是我为使其工作所做的更改:

containerView = UIView()
containerView.backgroundColor = #colorLiteral(red: 0.176470592617989, green: 0.498039215803146, blue: 0.756862759590149, alpha: 1.0)
scrollView.addSubview(containerView)
//containerView.frame = CGRect(x: 0, y: 0, width: 1080, height: 200)
containerView.translatesAutoresizingMaskIntoConstraints = false
containerView.topAnchor.constraint(equalTo:scrollView.topAnchor).isActive = true
containerView.leadingAnchor.constraint(equalTo:scrollView.leadingAnchor).isActive = true
containerView.trailingAnchor.constraint(equalTo:scrollView.trailingAnchor).isActive = true
containerView.bottomAnchor.constraint(equalTo:scrollView.bottomAnchor).isActive = true
containerView.heightAnchor.constraint(equalToConstant: 200).isActive = true
containerView.widthAnchor.constraint(equalToConstant: 1080).isActive = true

---

Why isn't my content scrolling?

要使其滚动，containerView 必须大于scrollView。您的错误是您设置了约束，使 containerView 与 scrollView 的宽度和高度相同，这就是您的内容不滚动的原因。

如果你想让它水平滚动，containerView的宽度必须大于scrollView的宽度。您可以通过以下两种方式之一执行此操作:

1. 为 containerView 指定一个显式恒定宽度，该宽度大于 scrollView 的宽度。

   或

2. 将 containerView 的 subview 从左到右链接起来，最左边的 subview 包含在 containerView 的前缘。完全指定 subview 的宽度，并在 subview 之间放置距离约束。最右边的 subview 必须与 containerView 的后缘有一个偏移量。通过这样做，Auto Layout 可以计算 containerView 的宽度并设置 scrollView 的 contentSize。

---

迷你项目:更新

这是您的迷你项目的一个版本，它使用一系列受约束的 View 来定义 containerView 的宽度。关键是 viewDidLoad() 中的 for 循环之后的最终约束，它将最后一个按钮的 trailingAnchor(又名 startPoint)连接到 containerView 的 trailingAnchor。这完成了连接 containerView 前缘和 containerView 后缘的约束和按钮链。有了这个，Auto Layout 就能够计算 containerView 的宽度并建立 scrollView 的 contentSize。

import UIKit
import PlaygroundSupport

class FilterViewController: UIViewController {
    var filterView: UIView!
    var scrollView: UIScrollView!
    var containerView: UIView!

    override func loadView() {
        filterView = UIView()
        view = filterView
        view.backgroundColor = #colorLiteral(red: 0.909803926944733, green: 0.47843137383461, blue: 0.643137276172638, alpha: 1.0)

        scrollView = UIScrollView()
        scrollView.backgroundColor = #colorLiteral(red: 0.474509805440903, green: 0.839215695858002, blue: 0.976470589637756, alpha: 1.0)
        view.addSubview(scrollView)
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.topAnchor.constraint(equalTo: view.topAnchor, constant: 40).isActive = true
        scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        scrollView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
        scrollView.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.25).isActive = true
        scrollView.isScrollEnabled = true

        containerView = UIView()
        containerView.backgroundColor = #colorLiteral(red: 0.176470592617989, green: 0.498039215803146, blue: 0.756862759590149, alpha: 1.0)
        scrollView.addSubview(containerView)
        containerView.translatesAutoresizingMaskIntoConstraints = false

        // This is key:  connect all four edges of the containerView to
        // to the edges of the scrollView
        containerView.topAnchor.constraint(equalTo: scrollView.topAnchor).isActive = true
        containerView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor).isActive = true
        containerView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor).isActive = true
        containerView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor).isActive = true

        // Making containerView and scrollView the same height means the
        // content will not scroll vertically
        containerView.heightAnchor.constraint(equalTo: scrollView.heightAnchor).isActive = true    
    }

    class Buttons {
        let button = UIButton()
        init(titleText: String) {
            button.backgroundColor = #colorLiteral(red: 0.976470589637756, green: 0.850980401039124, blue: 0.549019634723663, alpha: 1.0)
            button.setTitle(titleText, for: .normal)
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        let b1 = Buttons(titleText: "one")
        let b2 = Buttons(titleText: "two")
        let b3 = Buttons(titleText: "three")
        let b4 = Buttons(titleText: "four")
        let b5 = Buttons(titleText: "five")
        let buttonArray = [b1, b2, b3, b4, b5]
        var startPoint = containerView.leadingAnchor
        for btn in buttonArray {
            let theBtn = btn.button
            containerView.addSubview(theBtn)
            theBtn.translatesAutoresizingMaskIntoConstraints = false
            theBtn.leadingAnchor.constraint(equalTo: startPoint, constant: 20).isActive = true
            theBtn.topAnchor.constraint(equalTo: containerView.topAnchor).isActive = true
            theBtn.bottomAnchor.constraint(equalTo: containerView.bottomAnchor).isActive = true
            theBtn.widthAnchor.constraint(equalTo: theBtn.heightAnchor).isActive = true
            startPoint = theBtn.trailingAnchor
        }
        // Complete the chain of constraints
        containerView.trailingAnchor.constraint(equalTo: startPoint, constant: 20).isActive = true
    }
}

let filterViewController = FilterViewController()
PlaygroundPage.current.liveView = filterViewController