未能尝试以编程方式在滚动视图中添加UIView约束在SWIFT中

Question

所以我一直试图用约束以编程方式将UIVIew添加到UIScrollView。我只是没有在模拟器中看到UIView。 我有一个IBOutlet的UIScrollview ...所以我不知道为什么我遇到这个问题。

override func viewDidAppear(animated: Bool) { 

let ownerUIView:UIView! = UIView() 
     var innerLabel:UILabel = UILabel() 
     ownerUIView.translatesAutoresizingMaskIntoConstraints = false 
     innerLabel.translatesAutoresizingMaskIntoConstraints = false 
     innerLabel.text = "Test text" 
     ownerUIView.addSubview(innerLabel) 
     importantScroll.addSubview(ownerUIView) 
     ownerUIView.backgroundColor = UIColor.blueColor() 

     let constraint1 = NSLayoutConstraint(item: ownerUIView, attribute: NSLayoutAttribute.Leading, relatedBy: NSLayoutRelation.Equal, toItem: importantScroll, attribute: NSLayoutAttribute.Leading, multiplier: 1, constant: 10) 
     let constraint2 = NSLayoutConstraint(item: ownerUIView, attribute: NSLayoutAttribute.Trailing, relatedBy: NSLayoutRelation.Equal, toItem: importantScroll, attribute: NSLayoutAttribute.Trailing, multiplier: 1, constant: 10) 
     let constraint3 = NSLayoutConstraint(item: ownerUIView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1, constant: 60) 
     let constraint4 = NSLayoutConstraint(item: ownerUIView, attribute: .Top , relatedBy: .Equal, toItem: importantScroll, attribute: NSLayoutAttribute.Top , multiplier: 1, constant: 20) 

     NSLayoutConstraint.activateConstraints([constraint1,constraint2,constraint3,constraint4]) 

} 

我删除了约束，仍然无法看到UILabel或UIVIew。如果我删除UILable，那么我会看到蓝色的UIView。

let ownerUIView:UIView = UIView(frame: CGRect(x: 10, y: 10, width: 200, height: 200)) 
     let innerLabel:UILabel = UILabel(frame: CGRect(x: 10, y: 10, width: 100, height: 100)) 
     ownerUIView.translatesAutoresizingMaskIntoConstraints = false 
     innerLabel.translatesAutoresizingMaskIntoConstraints = false 
     innerLabel.text = "Test text" 
     ownerUIView.addSubview(innerLabel) 
     importantScroll.addSubview(ownerUIView) 
     ownerUIView.backgroundColor = UIColor.blueColor() 

Answer 1

我认为你需要设置你的ownerView和importantScoll之间宽度相等约束，因为你的滚动视图无法确定内容的大小，直到没有任何适当的宽度约束。你可以添加这一行。

let constraint5 = NSLayoutConstraint(item: ownerUIView, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: importantScroll, attribute: NSLayoutAttribute.Width, multiplier: 1.0, constant: 0.0) 
NSLayoutConstraint.activateConstraints([constraint1,constraint2,constraint3,constraint4,constraint5]) 

更新： 这是很常见的布局在滚动型多子视图时加入了滚动的内另一个容器的UIView。所以，我首先在Storyboard中添加了容器UIView。 ContainerView对scrollView具有相同的宽度和高度约束，并且我还添加了四个约束来将containerView约束到ScrollView。最后，我按照如下方式在体裁上设定了约束条件。

let constraint6 = NSLayoutConstraint(item: ownerView, attribute: NSLayoutAttribute.Leading, relatedBy: NSLayoutRelation.Equal, toItem: containerView, attribute: NSLayoutAttribute.Leading, multiplier: 1, constant: 40) 
let constraint7 = NSLayoutConstraint(item: containerView, attribute: .Tailing, relatedBy: .Equal, toItem: ownerView, attribute: .Trailing, multiplier: 1, constant: 10) 
let constraint8 = NSLayoutConstraint(item: ownerView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1, constant: 60) 
let constraint9 = NSLayoutConstraint(item: ownerView, attribute: .Top , relatedBy: .Equal, toItem: containerView, attribute: NSLayoutAttribute.Top , multiplier: 1, constant: 20) 

containerView.addConstraints([constraint6,constraint7,constraint8,constraint9])