在没有情节提要的情况下以编程方式添加容器视图？

Question

我的viewDidLoad 中有这个：

    let childViewControllerForPosts = PostsCollectionViewController(collectionViewLayout: UICollectionViewLayout())
    let cView = childViewControllerForPosts.view
    self.view.backgroundColor = UIColor.redColor()
    self.addChildViewController(childViewControllerForPosts)
    self.view.addSubview(cView)
    childViewControllerForPosts.didMoveToParentViewController(self)

    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(handleScroll(_:)), name: "cvScrolled", object: nil)

    cView.widthAnchor.constraintEqualToConstant(view.frame.size.width).active = true
    cView.heightAnchor.constraintEqualToConstant(view.frame.size.height).active = true
    cView.topAnchor.constraintEqualToAnchor(containerForGreyAndPurple.bottomAnchor).active = true
    cView.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor).active = true

但是，我收到一条错误消息，指出这是一个非法约束，因为它没有共同的祖先 :(

这是错误：

...because they have no common ancestor. Does the constraint reference items in different view hierarchies? That's illegal.'

Answer 1

您设置的约束不正确。

您需要先为父视图和容器视图添加约束，然后您还需要向容器控制器添加约束。 最后你应该在设置所有约束的末尾添加 didMoveToParent。

示例如下，你可以在你的情况下做类似的事情。

   NSLayoutConstraint.activateConstraints([
        containerView.leadingAnchor.constraintEqualToAnchor(view.leadingAnchor, constant: 10),
        containerView.trailingAnchor.constraintEqualToAnchor(view.trailingAnchor, constant: -10),
        containerView.topAnchor.constraintEqualToAnchor(view.topAnchor, constant: 10),
        containerView.bottomAnchor.constraintEqualToAnchor(view.bottomAnchor, constant: -10),
    ])


  NSLayoutConstraint.activateConstraints([
        controller.view.leadingAnchor.constraintEqualToAnchor(containerView.leadingAnchor),
        controller.view.trailingAnchor.constraintEqualToAnchor(containerView.trailingAnchor),
        controller.view.topAnchor.constraintEqualToAnchor(containerView.topAnchor),
        controller.view.bottomAnchor.constraintEqualToAnchor(containerView.bottomAnchor)
    ])


controller.didMoveToParentViewController(self)

Use autolayout to set dynamic UIView to match container view