swift - 以编程方式约束按钮

Question

我希望我的按钮保持在 x 轴中心，但我想在 y 轴上调整它。我的按钮是通过编程制作的，但我的注册页面主要是在 Storyboard上构建的。这使得按钮看起来与其他所有东西都不同

 super.viewDidLoad()


    button = dropDownBtn.init(frame: CGRect(x:0, y:0, width:0, height: 0))
    button.setTitle("BusinessType", for: .normal)
    button.translatesAutoresizingMaskIntoConstraints = false

    self.view.addSubview(button)

    PROBLEM !!!!!
    //button.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true

    //button.centerYAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true

    button.widthAnchor.constraint(equalToConstant: 200).isActive = true
    button.heightAnchor.constraint(equalToConstant: 40).isActive = true
    button.self.layer.cornerRadius = 10

    button.dropView.dropDownOptions = ["Apparel", "Artist", "Beauty", "Cosmetology", "Fitness", "Resturant","Photography"]

Answer 1

重新注释centerXAnchor和centerYAnchor约束

NSLayoutConstraint.activate([
  button.centerXAnchor.constraint(equalTo: self.view.centerXAnchor),
  button.centerYAnchor.constraint(equalTo: self.view.centerYAnchor,constant:-200), 
  button.widthAnchor.constraint(equalToConstant: 200),
  button.heightAnchor.constraint(equalToConstant: 40) 
])