Swift 在具有约束的UIView中移动UITextField

我正在制作一个应用程序，用户可以输入他们的汽车信息。我需要UITextFields向上移动，以便它们不被键盘覆盖。我是用这个代码做的

func textFieldDidBeginEditing(_ textField: UITextField)
{
    if make==textField
    {
        self.infoContainer.frame = self.infoContainer.frame.offsetBy(dx: 0, dy:-50)
    }
    if model==textField
    {
        self.infoContainer.frame = self.infoContainer.frame.offsetBy(dx: 0, dy:-75)
    }
    if color==textField
    {
        self.infoContainer.frame = self.infoContainer.frame.offsetBy(dx: 0, dy:-100)
    }
}

在我向UIView*infoContainer添加约束之前，这一点非常有效。那么它只能工作一次。比如，如果我点击Make，它会向上移动-50，或者如果我点击color，它会向上移动-100。但在那一次之后，它不会再移动了。比如，如果我点击Make，它会向上移动-50，但是如果我点击Color，它不会移动到-100。然后我试着改变约束条件

func textFieldDidBeginEditing(_ textField: UITextField)
    {
        if make==textField
        {
            infoContainer.translatesAutoresizingMaskIntoConstraints = false

            self.view.addSubview(infoContainer)

            let leadingConstraint = infoContainer.leadingAnchor.constraint(equalTo: self.view.leadingAnchor)
            let trailingConstraint = infoContainer.trailingAnchor.constraint(equalTo: self.view.trailingAnchor)
            let topConstraint = infoContainer.topAnchor.constraint(equalTo: self.view.topAnchor, constant: -50)
            let bottomConstraint = infoContainer.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: -50)

            initialConstraints.append(contentsOf: [leadingConstraint,trailingConstraint,topConstraint,bottomConstraint])

            NSLayoutConstraint.activate(initialConstraints)
        }
        if model==textField
        {
            infoContainer.translatesAutoresizingMaskIntoConstraints = false

            self.view.addSubview(infoContainer)

            let leadingConstraint = infoContainer.leadingAnchor.constraint(equalTo: self.view.leadingAnchor)
            let trailingConstraint = infoContainer.trailingAnchor.constraint(equalTo: self.view.trailingAnchor)
            let topConstraint = infoContainer.topAnchor.constraint(equalTo: self.view.topAnchor, constant: -75)
            let bottomConstraint = infoContainer.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: -75)

            initialConstraints.append(contentsOf: [leadingConstraint,trailingConstraint,topConstraint,bottomConstraint])

            NSLayoutConstraint.activate(initialConstraints)
        }
        if color==textField
        {
            infoContainer.translatesAutoresizingMaskIntoConstraints = false

            self.view.addSubview(infoContainer)

            let leadingConstraint = infoContainer.leadingAnchor.constraint(equalTo: self.view.leadingAnchor)
            let trailingConstraint = infoContainer.trailingAnchor.constraint(equalTo: self.view.trailingAnchor)
            let topConstraint = infoContainer.topAnchor.constraint(equalTo: self.view.topAnchor, constant: -100)
            let bottomConstraint = infoContainer.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: -100)

            initialConstraints.append(contentsOf: [leadingConstraint,trailingConstraint,topConstraint,bottomConstraint])

            NSLayoutConstraint.activate(initialConstraints)
        }
    }

---

这个效果好一点。如果我点击使其向上移动-50，然后模型向上移动-75，然后颜色向上移动-100。但它不会向下移动，就像我单击“后退”使它不会向下移动到-50。我甚至将颜色设置为+50。当我点击颜色时，它会下降+50，然后当我点击Make时，它会上升到-50，Model会上升到-75。但如果我再次单击“颜色”，它将不会移回+50。我哪里出错了？

问题是每次移动都要添加约束，这会随着时间的推移产生冲突，因此只需添加一次约束，然后调整要移动的约束的常量值，而不是执行此操作

1-将此代码段添加到

viewDidLoad

var bottomConstraint:NSLayoutConstraint!

//

二,-

如果愿意，您也可以对

topConstraint

执行相同的操作

infoContainer.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(infoContainer)
let leadingConstraint = infoContainer.leadingAnchor.constraint(equalTo: self.view.leadingAnchor)
let trailingConstraint = infoContainer.trailingAnchor.constraint(equalTo: self.view.trailingAnchor)
let topConstraint = infoContainer.topAnchor.constraint(equalTo: self.view.topAnchor, constant: -50)
bottomConstraint = infoContainer.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: -50)
initialConstraints.append(contentsOf: [leadingConstraint,trailingConstraint,topConstraint,bottomConstraint])
NSLayoutConstraint.activate(initialConstraints)

func textFieldDidBeginEditing(_ textField: UITextField)
{
    if make == textField
    {
        self.bottomConstraint.constant = -50
    }
    if model == textField
    {
        self.bottomConstraint.constant = -75
    }
    if color == textField
    {
        self.bottomConstraint.constant = -100
    }

   self.view.layoutIfNeeded()

   // you can animate it to

   /*
    UIView.animate(withDuration:0.5) {
      self.view.layoutIfNeeded()
    } */
}