ios - UIScrollView 在自动布局中尺寸不正确

Question

我正在尝试转换 Ray Wenderlich UIScrollView Tutorial 的第 1 部分使用通用设备进入自动布局。我目前在导航 Controller 中嵌入了一个 UITableView，将 ViewController 类的 UIViewController 与 UIScrollView (没有自定义类)。导航 Controller 有一个不透明的导航栏，没有工具栏。 UIViewController 的属性可以在下面相册的第一张图片中看到。

Image Album

仅使用四个 Storyboard约束(如下所述)，我的 View 看起来就像相册中的第二张图像，scrollView 的帧大小为不正确的 600x536 。为了解决这个问题，我决定在运行时在 ViewController.swift 的 viewDidLoad() 中再次添加约束。我现在总共有 8 个约束:

• Storyboard的 4 个限制:
  • scrollView.top = topLayoutGuide.bottom
  • scrollView.bottom = bottomLayoutGuide.top
  • scrollView.leading = superView.leading
  • scrollView.trailing = superView.trailing
• ViewController.swift 中的 4 个约束:
  • scrollView.top = topLayoutGuide
  • scrollView.bottom = view.bottom
  • scrollView.leading = view.leading
  • scrollView.trailing = view.trailing

由于这些限制，在缩放之前，我的 View 现在看起来像第三张专辑图像，scrollView 的帧大小仍然不正确的 375x667。缩放后，我的 View 是正确的，看起来像第四张专辑图像，scrollView 的帧大小为正确的375x603。其他一些注意事项:

• self.topLayoutGuide.length = 0。不应该是64吗？ 20 来自状态栏，44 来自导航栏？
• 删除 Storyboard限制会导致与没有程序化限制相同的问题。为什么 Storyboard约束仍然需要存在？
• 我尝试过纯方法和混合方法，但都没有解决这个问题。
• 以及在 Storyboard中禁用调整 ScrollView 插入、在顶部栏下延伸边缘和在不透明栏下延伸边缘(请参阅第一张图片)，我也在代码中禁用它们，但无济于事。
• 我无法使用插图，因为 UIScrollView 的框架在缩放后发生变化。

如何使 UIScrollView 保持恒定、适当的大小？

谢谢。

ViewController 类:UIViewController、UIScrollViewDelegate

@IBOutlet var scrollView: UIScrollView!

var imageView: UIImageView!

override func viewDidLoad() {
    super.viewDidLoad()

    //Reset the layout
    scrollView.needsUpdateConstraints()
    scrollView.setNeedsLayout()
    scrollView.layoutIfNeeded()

    //Set storyboard settings just in case
    scrollView.setTranslatesAutoresizingMaskIntoConstraints(false)
    self.extendedLayoutIncludesOpaqueBars = false
    self.edgesForExtendedLayout = .None
    self.automaticallyAdjustsScrollViewInsets = false
    self.navigationController?.navigationBar.translucent = false

    //Manually added constraints at runtime
    var constraintTS = NSLayoutConstraint(item: scrollView, attribute: .Top, relatedBy: .Equal, toItem: topLayoutGuide, attribute: .Bottom, multiplier: 1.0, constant: 0)
    var constraintBS = NSLayoutConstraint(item: scrollView, attribute: .Bottom, relatedBy: .Equal, toItem: view, attribute: .Bottom, multiplier: 1.0, constant: 0)
    var constraintLS = NSLayoutConstraint(item: scrollView, attribute: .Leading, relatedBy: .Equal, toItem: view, attribute: .Leading, multiplier: 1.0, constant: 0)
    var constraintRS = NSLayoutConstraint(item: scrollView, attribute: .Trailing, relatedBy: .Equal, toItem: view, attribute: .Trailing, multiplier: 1.0, constant: 0)
    view.addConstraint(constraintTS)
    view.addConstraint(constraintBS)
    view.addConstraint(constraintLS)
    view.addConstraint(constraintRS)

    println(scrollView.frame.width)
    println(scrollView.frame.height)

    //Original Ray Wenderlich code
    let image1 = UIImage(named: "photo1")!
    imageView = UIImageView(image: image1)
    imageView.frame = CGRect(origin: CGPoint(x: 0, y: 0), size: image1.size)
    scrollView.addSubview(imageView)
    scrollView.contentSize = image1.size

    let scrollViewFrame = scrollView.frame
    let scaleWidth = scrollViewFrame.width / scrollView.contentSize.width
    let scaleHeight = scrollViewFrame.height / scrollView.contentSize.height
    let minScale = min(scaleWidth, scaleHeight)
    scrollView.minimumZoomScale = minScale
    scrollView.maximumZoomScale = 1.0
    scrollView.zoomScale = minScale

    centerScrollViewContents()
}

func centerScrollViewContents() {
    let boundsSize = scrollView.bounds.size
    var contentsFrame =  imageView.frame

    if contentsFrame.size.width < boundsSize.width {
        contentsFrame.origin.x = (boundsSize.width - contentsFrame.width) / 2.0
    } else {
        contentsFrame.origin.x = 0.0
    }

    if contentsFrame.size.height < boundsSize.height {
        contentsFrame.origin.y = (boundsSize.height - contentsFrame.height) / 2.0
        println("boundsSize.height: \(boundsSize.height)")
        println("boundsSize.width:  \(boundsSize.width)")
        println("contentsFrame.origin.y: \(contentsFrame.origin.y)")
    } else {
        contentsFrame.origin.y = 0.0
    }

    imageView.frame = contentsFrame
}

func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
    return imageView
}

func scrollViewDidZoom(scrollView: UIScrollView) {
    centerScrollViewContents()
}

override func viewWillLayoutSubviews() {
    println(self.topLayoutGuide.length)
}

Answer 1

解决了!感谢Working with Top Layout Guide in UIScrollView through Auto Layout 。我不认为 UIScrollView 会让 topLayoutGuide 表现不同，但显然确实如此。事实证明我不需要设置约束； scrollView.layoutIfNeeded() 就可以了!我的scrollView现在是一个常量375x667，消除了调整大小问题并给出self.topLayoutGuide.length = 64。这允许我通过减去self.topLayoutGuide.length来垂直居中 View > 在 centerScrollViewContents() 中。我还在 viewWillLayoutSubviews() 中调用 centerScrollViewContents()。这是我的新代码:

@IBOutlet var scrollView: UIScrollView!

var imageView: UIImageView!

override func viewDidLoad() {
    super.viewDidLoad()

    //Redo constraints at runtime
    scrollView.layoutIfNeeded()

    //Original Ray Wenderlich code
    let image1 = UIImage(named: "photo1")!
    imageView = UIImageView(image: image1)
    imageView.frame = CGRect(origin: CGPoint(x: 0, y: 0), size: image1.size)
    scrollView.addSubview(imageView)
    scrollView.contentSize = image1.size

    let scrollViewFrame = scrollView.frame
    let scaleWidth = scrollViewFrame.width / scrollView.contentSize.width
    let scaleHeight = scrollViewFrame.height / scrollView.contentSize.height
    let minScale = min(scaleWidth, scaleHeight)
    scrollView.minimumZoomScale = minScale
    scrollView.maximumZoomScale = 1.0
    scrollView.zoomScale = minScale
}
func centerScrollViewContents() {
    let boundsSize = scrollView.bounds.size
    var contentsFrame =  imageView.frame

    if contentsFrame.size.width < boundsSize.width {
        contentsFrame.origin.x = (boundsSize.width - contentsFrame.width) / 2.0
    } else {
        contentsFrame.origin.x = 0.0
    }

    if contentsFrame.size.height < boundsSize.height {
        contentsFrame.origin.y = (boundsSize.height - contentsFrame.height - self.topLayoutGuide.length) / 2.0
    } else {
        contentsFrame.origin.y = 0.0
    }

    imageView.frame = contentsFrame
}

override func viewWillLayoutSubviews() {
    println(self.topLayoutGuide.length)
    centerScrollViewContents()
}

所有其他功能均未更改。