没有显示VFL约束的场景基座视图

Question

我有一个View Controller，它的一个UIView（名为pickerView）放置在Scene Dock中。我使用Scene Dock的原因是该UIView将包含许多子视图，并且我不想弄乱情节提要。我正在使用VFL调整pickerView的大小，因此它是设备的全屏。

问题是，当我按openPickerButtonPressed时，黄色的pickerView永远不会显示。我在这里想念什么吗？ VFL约束是否设置正确？

override func viewDidLoad() {
    super.viewDidLoad()
    self.pickerView.translatesAutoresizingMaskIntoConstraints = false

}

@IBAction func openPickerButtonPressed(_ sender: UIButton) {
    guard pickerView.superview == nil else {
        return
    }
    self.view.addSubview(pickerView)
    let viewsDictionary: [String: UIView] = ["pickerView": pickerView]
    view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-0-[pickerView]-0-|", options: [], metrics: nil, views: viewsDictionary))
    view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:[pickerView(0)]", options: [], metrics: nil, views: viewsDictionary)) // HEIGHT
    view.addConstraint(NSLayoutConstraint(item: pickerView, attribute: .centerY, relatedBy: NSLayoutConstraint.Relation(rawValue: 0)!, toItem: view, attribute: .centerY, multiplier: 1, constant: 0))
}

如何在按下openPickerButtonPressed按钮时打开pickerView UIView？