swift - 添加约束困惑 View

Question

我有一个带有 UICollectionView 和 UISegmentedControl 的 View 。

我想更改约束，以便段 Controller 不会与 Collection View 重叠，如下图所示:

这是我的代码:

override func viewDidLoad()
    {
        super.viewDidLoad()

        self.navigationItem.leftBarButtonItem = nil
        self.tabBarController?.tabBar.isHidden = true


        self.SegmentController.setTitle(SegmentAtext, forSegmentAt: 0)
        self.SegmentController.setTitle(SegmentBtext, forSegmentAt: 1)


        self.view.bringSubview(toFront: SegmentController)

        self.LoadProducts(productsToShow: SegmentAtype)
    }

所以我添加这个命令:

self.ProductsCollection.topAnchor.constraint(equalTo: SegmentController.bottomAnchor, constant: 10).isActive = true

但结果更糟:

现在段 Controller 几乎完全隐藏了!

如何解决这个问题？

编辑:

我的viewDidLayoutSubviews函数:

override func viewDidLayoutSubviews()
    {
        ProductsCollection.translatesAutoresizingMaskIntoConstraints = false
        let topConstraint = NSLayoutConstraint(item: ProductsCollection, attribute: .top, relatedBy: .equal, toItem: self.view, attribute: .top, multiplier: 1, constant: 20)
        let bottomConstraint = NSLayoutConstraint(item: ProductsCollection, attribute: .bottom, relatedBy: .equal, toItem: self.view, attribute: .bottom, multiplier: 1, constant: -50) //leaving space for search field
        let leadingConstraint = NSLayoutConstraint(item: ProductsCollection, attribute: .leading, relatedBy: .equal, toItem: self.view, attribute: .leading, multiplier: 1, constant: 0)
        let trailingConstraint = NSLayoutConstraint(item: ProductsCollection, attribute: .trailing, relatedBy: .equal, toItem: self.view, attribute: .trailing, multiplier: 1, constant: 0)

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

注意:

我的viewDidLayoutSubviews是在 super View 中实现的，它不包含UISegmentedControl。 UISegmentedControl 包含在继承 View 中。

编辑:更新的 View

Answer 1

如果您希望 UISegmentedControl 位于屏幕中央并在屏幕下方显示您的 Collection View

NSLayoutConstraint.activate([
    segmentedControl.topAnchor.constraint(equalTo: view.topAnchor),
    segmentedControl.centerXAnchor.constraint(equalTo: view.centerXAnchor),
    collectionView.topAnchor.constraint(equalTo: segmentedControl.bottomAnchor),
    collectionView.leftAnchor.constraint(equalTo: view.leftAnchor),
    collectionView.rightAnchor.constraint(equalTo: view.rightAnchor),
    collectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])

因此，我们在 View 顶部设置了分段控件，并将其居中，那么 Collection View 的顶部是分段控件的底部(如果需要，您可以添加一个常量用于填充)，并且 View 的左右和底部