ios - Xcode Swift 以编程方式将 UITextfield X 位置设置为中心

Question

我尝试将文本字段的 X 位置置于页面 View Controller 的中心。这就是我现在的编程方式:

  lastnamefield =  UITextField(frame: CGRect(x: 100.33, y:431.33 , width: 206, height: 34))
        lastnamefield.backgroundColor = .clear
        lastnamefield.placeholder = "Last name"
        lastnamefield.textColor = .black
        lastnamefield.font = UIFont(name: "Futura", size: 20)
        lastnamefield.borderStyle = UITextField.BorderStyle.roundedRect
          lastnamefield.autocorrectionType = UITextAutocorrectionType.no
          lastnamefield.keyboardType = UIKeyboardType.default
          lastnamefield.returnKeyType = UIReturnKeyType.done
          lastnamefield.clearButtonMode = UITextField.ViewMode.whileEditing
          lastnamefield.contentVerticalAlignment = UIControl.ContentVerticalAlignment.center
      //  lastnamefield.delegate = self as! UITextFieldDelegate
          self.view.addSubview(lastnamefield)






    emailfield =  UITextField(frame: CGRect(x: 100.33, y:488 , width: 206, height: 34))
        emailfield.backgroundColor = .clear
        emailfield.placeholder = "Email Adress"
        emailfield.textColor = .black
        emailfield.font = UIFont(name: "Futura", size: 20)
        emailfield.borderStyle = UITextField.BorderStyle.roundedRect
          emailfield.autocorrectionType = UITextAutocorrectionType.no
          emailfield.keyboardType = UIKeyboardType.default
          emailfield.returnKeyType = UIReturnKeyType.done
          emailfield.clearButtonMode = UITextField.ViewMode.whileEditing
          emailfield.contentVerticalAlignment = UIControl.ContentVerticalAlignment.center
      //  emailfield.delegate = self as! UITextFieldDelegate
          self.view.addSubview(emailfield)

我知道这显然不会使其居中，但我已经尝试过这样的事情:

emailfield.widthAnchor.constraint(equalTo: revealingSplashView.widthAnchor, multiplier: 0.8).isActive = true
imageView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
emailfield.heightAnchor.constraint(equalToConstant: 25).isActive = true
emailfield.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true

我的应用程序要么崩溃，要么出错。我对这个约束的东西有点陌生，我必须以编程方式完成它，因为我的 pageviewcontroller 也是以编程方式。我为我糟糕的写作技巧道歉。我不是英国人。

Answer 1

1-这会崩溃

emailfield.delegate = self as! UITextFieldDelegate

相反

emailfield.delegate = self

并使 vc 符合

class VC:UIViewController,UITextFieldDelegate {

2-

添加约束时不要忘记设置

self.emailfield.translatesAutoresizingMaskIntoConstraints = false

3-对于您设置的电子邮件，宽度，高度和centerX，您还需要设置y约束centerY，顶部或底部