ios - 无法使用纯自动布局约束创建 UIScrollerView

Question

我精简了代码，以便于理解。

假设您有一个 Controller ，并且想要使用纯自动布局添加一个简单的滚动条。

您可以按如下方式调用我的函数工具(如下提供):

// Create scroll view
let strip = addStripCategoryTo(view)

// Attach it to the view, vertically and horizontally
strip.topAnchor.constraintEqualToAnchor(view.topAnchor).active = true
strip.leftAnchor.constraintEqualToAnchor(view.leftAnchor).active = true


// The function
func addStripCategoryTo(parent: UIView) -> UIView {

    let h:CGFloat = 128
    let w = 2*h/3
    let n = 5
    let width  = w * CGFloat(n)
    let height = h

    // Scroll view
    let scrollview = UIScrollView()
    parent.addSubview(scrollview)

    scrollview.scrollEnabled = true
    scrollview.translatesAutoresizingMaskIntoConstraints = false
    scrollview.widthAnchor .constraintEqualToAnchor(parent.widthAnchor).active = true
    scrollview.heightAnchor.constraintEqualToConstant(h).active = true

    scrollview.layer.borderWidth = 2
    scrollview.layer.borderColor = UIColor.greenColor().CGColor
    scrollview.backgroundColor = UIColor.brownColor()

    // Scroll view content
    let contentView = UIView() //frame:CGRect(origin: CGPointZero, size:CGSize(width: width, height: height)))
    scrollview.addSubview(contentView)
    contentView.backgroundColor = UIColor.redColor()
    contentView.layer.borderWidth = 10
    contentView.layer.borderColor = UIColor.blueColor().CGColor
    contentView.translatesAutoresizingMaskIntoConstraints = false
    contentView.centerYAnchor.constraintEqualToAnchor(scrollview.centerYAnchor).active = true
    contentView.widthAnchor .constraintEqualToConstant(width).active = true
    contentView.heightAnchor.constraintEqualToConstant(height).active = true

    return scrollview
}

不幸的是，我无法水平滚动，请参见截图:

我错过了什么？

Answer 1

你的约束应该是这样的，

ScrollView - 顶部、底部、前导、尾随

ContentView - 顶部、底部、前导、尾随、固定宽度、在容器中垂直居中(中心 y)

并且您的内容 View 的宽度应该大于屏幕宽度，那么您也可以水平滚动希望这会有所帮助:)