swift - 如何以编程方式对我在容器 View 中调用的 ViewController 施加约束？

Question

我对三个具有滚动类型的 Controller 使用了PageViewController。现在我在 containerView 中调用了这个 PageViewController，这里的问题是容器高度小于 PageViewController 的高度，我能够在 containerView 中调用 PageViewController 但底部正在退出视野。我尝试以编程方式放置自动布局，但它不起作用。请告诉我如何解决这个问题？

@IBOutlet weak var containerView: UIView!


    override func viewDidLoad() {
        super.viewDidLoad()
        let storyboard = UIStoryboard.init(name: "Main", bundle: nil)
        let controller = storyboard.instantiateViewController(withIdentifier: "ViewController")
        self.setControllerFrame(controller: controller )
        addChild(controller)
        self.containerView.addSubview(controller.view)

    }

    func setControllerFrame(controller: UIViewController){
        //Validating frames according to orientation
        self.view.setNeedsDisplay()
        self.view.layoutIfNeeded()
        //*******temp fix:******** this is solutions for a single device not for all devices(screen sizes).
        if (self.view.frame.size.width < self.view.frame.size.height){
        controller.view.frame = CGRect.init(x: 0, y: 0, width: self.view.frame.size.width, height: self.view.frame.size.height)
        } else if (self.view.frame.size.width >= self.view.frame.size.height){
        controller.view.frame = CGRect.init(x: 0, y: 0, width: self.view.frame.size.height, height: self.view.frame.size.width)
        }
         //tried this but crashes at last line.
        controller.view.translatesAutoresizingMaskIntoConstraints = false
        let topConstraint = NSLayoutConstraint(item: controller.view!, attribute: NSLayoutConstraint.Attribute.top, relatedBy: NSLayoutConstraint.Relation.equal, toItem: self.containerView, attribute: NSLayoutConstraint.Attribute.top, multiplier: 1, constant: 0)
        let bottomConstraint = NSLayoutConstraint(item: controller.view!, attribute: NSLayoutConstraint.Attribute.bottom, relatedBy: NSLayoutConstraint.Relation.equal, toItem: self.containerView, attribute: NSLayoutConstraint.Attribute.bottom, multiplier: 1, constant: 0)
        let leadingConstraint = NSLayoutConstraint(item: controller.view!, attribute: NSLayoutConstraint.Attribute.leading, relatedBy: NSLayoutConstraint.Relation.equal, toItem: self.containerView, attribute: NSLayoutConstraint.Attribute.leading, multiplier: 1, constant: 0)
        let trailingConstraint = NSLayoutConstraint(item: controller.view!, attribute: NSLayoutConstraint.Attribute.trailing, relatedBy: NSLayoutConstraint.Relation.equal, toItem: self.containerView, attribute: NSLayoutConstraint.Attribute.trailing, multiplier: 1, constant: 0)
        view.addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint])
}

上面的代码********temp fix:********解决了我针对单个设备屏幕的问题，但不适用于所有设备。所以请让我知道一个正确的解决方案

Answer 1

1- viewDidLoad 内部 frame 尚不正确，因此将其设置在 viewDidLayoutSubviews

内部

controller.view.frame  = // value

2-崩溃了

view.addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint])

因为您应该在设置约束之前添加 subview

self.containerView.addSubview(controller.view)