Question

我有一个滚动视图，里面有一个故事板中的imageview。我有这个代码所在的文件的iboutlet，并引用了这些视图。它们分别称为scrollView和graph。我试图以编程方式在scrollview中的图形下面添加很多UILabel，但是我甚至无法显示它。

我添加的宽度约束不会导致任何问题，但其他三个约束会导致运行时错误The view hierarchy is not prepared for the constraint。我想将标签的顶部限制在图形的底部，标签的左侧限制在scrollview的左侧，标签的底部限制在scrollview的底部。我做错了什么？

更新代码：

  var noteBodyLabel = UILabel()
  noteBodyLabel.text = "test asdf  asd fasdf a sdf asdf as dfa sdf  safd"

  noteBodyLabel.setTranslatesAutoresizingMaskIntoConstraints(false)



  var widthCons = NSLayoutConstraint(
     item: noteBodyLabel,
     attribute: .Width,
     relatedBy: .Equal,
     toItem: nil,
     attribute: .NotAnAttribute,
     multiplier: 1, constant: 280)


  let topCons = NSLayoutConstraint(
     item: noteBodyLabel,
     attribute: .Top,
     relatedBy: .Equal,
     toItem: graph,
     attribute: .Bottom,
     multiplier: 1, constant: 0);


  let bottomCons = NSLayoutConstraint(
     item: noteBodyLabel,
     attribute: .Bottom,
     relatedBy: .Equal,
     toItem: scrollView,
     attribute: .Bottom,
     multiplier: 1, constant: 0);

  let leftCons = NSLayoutConstraint(
     item: noteBodyLabel,
     attribute: .Left,
     relatedBy: .Equal,
     toItem: scrollView,
     attribute: .Left,
     multiplier: 1, constant: 0);

  scrollView.addSubview(noteBodyLabel)
  noteBodyLabel.addConstraints([topCons,leftCons,bottomCons,widthCons])

Answer 1

我发现我必须将约束添加到self.view，而不是note1或任何其他元素。

  var note1 = UILabel()
  note1.text = "test asdf  asd fasdf a sdf asdf as dfa sdf  safd"

  note1.setTranslatesAutoresizingMaskIntoConstraints(false)
  scrollView.addSubview(note1)

  var widthCons = NSLayoutConstraint(
     item: note1,
     attribute: .Width,
     relatedBy: .Equal,
     toItem: nil,
     attribute: .NotAnAttribute,
     multiplier: 1, constant: 280)


  let topCons = NSLayoutConstraint(
     item: note1,
     attribute: .Top,
     relatedBy: .Equal,
     toItem: graph,
     attribute: .Bottom,
     multiplier: 1, constant: 0);

  let bottomCons = NSLayoutConstraint(
     item: note1,
     attribute: .Bottom,
     relatedBy: .Equal,
     toItem: scrollView,
     attribute: .Bottom,
     multiplier: 1, constant: 0);

  let leftCons = NSLayoutConstraint(
     item: note1,
     attribute: .Left,
     relatedBy: .Equal,
     toItem: scrollView,
     attribute: .Left,
     multiplier: 1, constant: 0);

  self.view.addConstraints([topCons, bottomCons, leftCons, widthCons])

使用AutoLayout以编程方式将UILabel添加到ScrollView（swift）

1 个答案: