约束并没有扩大我对方向变化的看法

Question

我创建了我的视图：

    self.scrollView = UIScrollView()
    self.scrollView.delegate = self
    self.scrollView.contentSize = CGSizeMake(UIScreen.mainScreen().bounds.width, 1000)
    containerView = UIView()
    containerView.backgroundColor = UIColor.redColor()
    scrollView.translatesAutoresizingMaskIntoConstraints    = false
    containerView.translatesAutoresizingMaskIntoConstraints = false
    scrollView.addSubview(containerView)
    view.addSubview(scrollView)

然后我添加了这些约束：

    // Constraint ScrollView
    view.addConstraint(NSLayoutConstraint(item: scrollView, attribute: .Top, relatedBy: .Equal, toItem: view, attribute: .Top, multiplier: 1.0, constant: 0.0))
    view.addConstraint(NSLayoutConstraint(item: scrollView, attribute: .Bottom, relatedBy: .Equal, toItem: view, attribute: .Bottom, multiplier: 1.0, constant: 0.0))
    view.addConstraint(NSLayoutConstraint(item: scrollView, attribute: .Leading, relatedBy: .Equal, toItem: view, attribute: .Leading, multiplier: 1.0, constant: 0.0))
    view.addConstraint(NSLayoutConstraint(item: scrollView, attribute: .Trailing, relatedBy: .Equal, toItem: view, attribute: .Trailing, multiplier: 1.0, constant: 0.0))
    // Constraint ContainerView
    scrollView.addConstraint(NSLayoutConstraint(item: containerView, attribute: NSLayoutAttribute.Top, relatedBy: NSLayoutRelation.Equal, toItem: scrollView, attribute: NSLayoutAttribute.Top, multiplier: 1.0, constant: 0.0))
    scrollView.addConstraint(NSLayoutConstraint(item: containerView, attribute: NSLayoutAttribute.Bottom, relatedBy: NSLayoutRelation.Equal, toItem: scrollView, attribute: NSLayoutAttribute.Bottom, multiplier: 1.0, constant: 0.0))
    scrollView.addConstraint(NSLayoutConstraint(item: containerView, attribute: NSLayoutAttribute.Leading, relatedBy: NSLayoutRelation.Equal, toItem: scrollView, attribute: NSLayoutAttribute.Leading, multiplier: 1.0, constant: 0.0))
    scrollView.addConstraint(NSLayoutConstraint(item: containerView, attribute: NSLayoutAttribute.Trailing, relatedBy: NSLayoutRelation.Equal, toItem: scrollView, attribute: NSLayoutAttribute.Trailing, multiplier: 1.0, constant: 0.0))

而这个：

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    scrollView.frame    = view.bounds
    containerView.frame = CGRectMake(0, 0, scrollView.contentSize.width, scrollView.contentSize.height)
}

但是当我改变方向时，containerView的宽度保持不变。如何确保宽度扩展到新布局scrollView的宽度？

Answer 1

你应该替换

scrollView.addConstraint(NSLayoutConstraint(item: containerView, attribute: NSLayoutAttribute.Bottom, relatedBy: NSLayoutRelation.Equal, toItem: scrollView, attribute: NSLayoutAttribute.Bottom, multiplier: 1.0, constant: 0.0))
scrollView.addConstraint(NSLayoutConstraint(item: containerView, attribute: NSLayoutAttribute.Leading, relatedBy: NSLayoutRelation.Equal, toItem: scrollView, attribute: NSLayoutAttribute.Leading, multiplier: 1.0, constant: 0.0))

跟

view.addConstraint(NSLayoutConstraint(item: containerView, attribute: .Height, relatedBy: .Equal, toItem: scrollView, attribute: .Height, multiplier: 1.0, constant: 0.0))
view.addConstraint(NSLayoutConstraint(item: containerView, attribute: .Width, relatedBy: .Equal, toItem: scrollView, attribute: .Width, multiplier: 1.0, constant: 0.0))

这将使用滚动视图的

宽度和高度，而不是将容器视图拉伸到滚动视图的右侧和底部。它似乎工作得更好。根据文档，我还将约束添加到了共同祖先，但它也可以通过添加到 scrollView 来工作，因此您可以选择是否要将所有约束添加到视图而不是 scrollView。

进一步说明

在 iOS 8 及更高版本中，您只需激活约束即可，而无需将其添加到视图中。

NSLayoutConstraint(item: containerView, attribute: .Top, relatedBy: .Equal, toItem: scrollView, attribute: .Top, multiplier: 1.0, constant: 0.0).active = true

在我更喜欢的iOS 9中，您可以使用锚点，例如

scrollView.topAnchor.constraintEqualToAnchor(topLayoutGuide.bottomAnchor).active = true

您无需在布局子视图中执行任何操作。translatesAutoresizeMaskIntoConstraint属性确实应该设置为false NOT true。

Answer 2

您还应该添加这些约束

containerView.addConstraint(NSLayoutConstraint(item: containerView, attribute: .Top, relatedBy: .Equal, toItem: scrollView, attribute: .Top, multiplier: 1.0, constant: 0.0))
containerView.addConstraint(NSLayoutConstraint(item: containerView, attribute: .Bottom, relatedBy: .Equal, toItem: scrollView, attribute: .Bottom, multiplier: 1.0, constant: 0.0))
containerView.addConstraint(NSLayoutConstraint(item: containerView, attribute: .Leading, relatedBy: .Equal, toItem: scrollView, attribute: .Leading, multiplier: 1.0, constant: 0.0))
containerView.addConstraint(NSLayoutConstraint(item: containerView, attribute: .Trailing, relatedBy: .Equal, toItem: scrollView, attribute: .Trailing, multiplier: 1.0, constant: 0.0))