Swift iOS-如何设置UIView的高度锚<=到标签的内在文本大小？'NSLayoutConstraint'不能转换为'Bool'

Question

我有一个程序化视图,里面有一个标签,我固定在navBar的底部.标签内部会有动态文本,如果文本的高度变小,我希望标签所在的视图至少为64磅或更大.

此标签中文本的内在大小将视图设置在显着高度.

setViewAndLabel(dynamicText: "Unknown Error\nPlease try your request again\Error: 123")

但是,此文本的内在大小使高度变小:

setViewAndLabel(dynamicText: "Message Deleted!")

该留言删除!应该更符合:

我使用了一些返回键来设置它,但我不认为这是正确的方法,因为将生成不同的消息:

setViewAndLabel(dynamicText: "\nMessage Deleted!\n")

我也尝试过:

if myView.heightAnchor.constraint(lessThanOrEqualToConstant: 64){
     myView.heightAnchor.constraint(equalToConstant: 64).isActive = true
}

但我得到错误:

'NSLayoutConstraint'不能转换为'Bool'

设置标签高度到最小高度的最佳方法是什么？

var myLabel: UILabel(){
   let label = UILabel()
   label.translatesAutoresizingMaskIntoConstraints = false
   label.textColor = UIColor.white
   label.font = UIFont(name: "Helvetica-Regular", size: 19)
   label.numberOfLines = 0
   label.sizeToFit()
   label.textAlignment = .center
   return label
}

let myView:UIView = {
   let view = UIView()
   view.translatesAutoresizingMaskIntoConstraints = false
   return view
}()

override func viewWillAppear(_ animated: Bool)
   super.viewWillAppear(animated){

   setViewAndLabel(dynamicText: //some text will get set here)
}

func setViewAndLabel(dynamicText: String){
   view.addSubView(myView)
   myView.backgroundColor = UIColor.red
   myView.topAnchor.constraint(equalTo: view.topAnchor, constant: 64).isActive = true
   View.widthAnchor.constraint(equalTo: view.widthAnchor, constant: 0).isActive = true

   myView.addSubView(myLabel)
   myLabel.text = dynamicText
   myLabel.topAnchor.constraint(equalTo: myView.topAnchor, constant: 0).isActive = true
   myLabel.widthAnchor.constraint(equalTo: myView.widthAnchor, constant: 0).isActive = true
   myView.bottomAnchor.constraint(equalTo: myLabel.bottomAnchor, constant: 0).isActive = true

   //this if statement doesn't work
   if myView.heightAnchor.constraint(lessThanOrEqualToConstant: 64){
        viewForErrorLabel.heightAnchor.constraint(equalToConstant: 64).isActive = true
   }
}

Answer 1

这是你必须设置约束的方法:

view.addSubview(myView)
myView.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor).isActive = true
myView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
myView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true

myView.heightAnchor.constraint(greaterThanOrEqualToConstant: 64).isActive = true

myView.addSubview(myLabel)
myLabel.topAnchor.constraint(equalTo: myView.topAnchor).isActive = true
myLabel.leadingAnchor.constraint(equalTo: myView.leadingAnchor).isActive = true
myLabel.trailingAnchor.constraint(equalTo: myView.trailingAnchor).isActive = true
myLabel.bottomAnchor.constraint(equalTo: myView.bottomAnchor).isActive = true

您根本不需要检查标签的高度.您可以简单地始终创建大于或等于约束myView的高度,并且其高度永远不会小于64pt(或您设置的任何值) - 即使标签包含非常短的文本.