ios - 仅当 UIView 已布局时才发送数据源信息？

Question

我无法理解这一点。我早些时候已经能够完成这样的项目，但现在类似的方法对我不起作用。

问题是这样的:我有一个 UIPageViewController，它有 4 个 StoryViewController。每个storyViewControllers都有一个自定义的containerView。我想在 containerView 上添加“n”个 UIViews。我正在从 View Controller 发送 dataSource 或“n”。但是，我无法在容器 View 上正确布置 subview 。

本质上我想知道何时从 View Controller 发送数据源信息。显然，我想在添加自定义容器 View 后发送它。

我正在使用viewDidLayoutSubviews。这使它起作用。但是，我认为这不是正确的方法。现在，每次 View Controller 布置 subview 时，我的委托(delegate)都会被调用。

我尝试在 viewDidLoad() 中执行此操作，但这也不起作用。

这有效。但似乎不太对劲。阿尔斯我的 storyViewController 代码

    override func viewDidLoad() {
    super.viewDidLoad()
    segmentContainerView = ATCStorySegmentsView()
    view.addSubview(segmentContainerView)
    configureSegmentContainerView()
    segmentContainerView.translatesAutoresizingMaskIntoConstraints = false

}

  override func viewDidLayoutSubviews() {
    segmentContainerView.delegate = self
     DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
        self.segmentContainerView.startAnimation() // I am also animating these views that are laid on the containerView. Doing them here starts the animation randomly whenever I scroll through the UIPageController
    }
}

在containerView中:

    var delegate: ATCSegmentDataSource? {
    didSet {
        addSegments()
    }
}

private func addSegments() {
    let numberOfSegment = delegate?.numberOfSegmentsToShow()
    guard let segmentQuantity = numberOfSegment else { return }
    layoutIfNeeded()
    setNeedsLayout()
    for i in 0..<segmentQuantity {
        let segment = Segment()
        addSubview(segment.bottomSegment)
        addSubview(segment.topSegment)
        configureSegmentFrame(index: i, segmentView: segment)
        segmentsArray.append(segment)
    }


}

private func configureSegmentFrame(index: Int, segmentView: Segment) {
    let numberOfSegment = delegate?.numberOfSegmentsToShow()
    guard let segmentQuantity = numberOfSegment else { return }

    let widthOfSegment : CGFloat = (self.frame.width - (padding * CGFloat(segmentQuantity - 1))) / CGFloat(segmentQuantity)

    let i = CGFloat(index)

    let segmentFrame = CGRect(x: i * (widthOfSegment + padding), y: 0, width: widthOfSegment, height: self.frame.height)
    segmentView.bottomSegment.frame = segmentFrame
    segmentView.topSegment.frame = segmentFrame
    segmentView.topSegment.frame.size.width = 0

}

这按其应有的方式工作。但是当我滚动 UIPageViewController 时，动画并不总是从头开始。因为它依赖于布局 subview 。有时，如果我慢慢地滚动页面 Controller ， subview 会再次布局，动画会从头开始。其他时候，当 View 已经加载时，动画会从我留下的位置开始。

问题我想知道将数据源从 View Controller 发送到容器 View 的最佳方式是什么？该数据源是生成要添加到containerView 上的 View 数量所需的数据源。

这是我从 viewDidLayoutSubviews 发送数据源时得到的结果。我今天早些时候问了另一个问题，其中列出了我用于发送数据源的其他方法。也看看:Not able to lay out Subviews on a custom UIView in Swift

Answer 1

这是一个非常基本的示例...

它有:

• Segment: UIView 子类，包含“bottomSegment”和“topSegment”
• 一个 ATCStorySegmentsView: UIView 子类，带有 UIStackView 来布局所需数量的段
• StoryViewController: UIViewController 子类，在其 View 顶部添加 ATCStorySegmentsView，然后告诉该 View 为 viewDidAppear( )

<小时/>

class Segment: UIView {

    let topSegment: UIView = {
        let v = UIView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .white
        return v
    }()

    let bottomSegment: UIView = {
        let v = UIView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .gray
        return v
    }()

    var startConstraint: NSLayoutConstraint = NSLayoutConstraint()
    var endConstraint: NSLayoutConstraint = NSLayoutConstraint()

    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func commonInit() -> Void {
        addSubview(bottomSegment)
        addSubview(topSegment)

        // start constraint has width of Zero
        startConstraint = topSegment.widthAnchor.constraint(equalTo: bottomSegment.widthAnchor, multiplier: 0.0)

        // end constraint has width of bottomSegment
        endConstraint = topSegment.widthAnchor.constraint(equalTo: bottomSegment.widthAnchor, multiplier: 1.0)

        NSLayoutConstraint.activate([

            // bottomSegment constrained to all 4 sides
            bottomSegment.topAnchor.constraint(equalTo: topAnchor),
            bottomSegment.bottomAnchor.constraint(equalTo: bottomAnchor),
            bottomSegment.leadingAnchor.constraint(equalTo: leadingAnchor),
            bottomSegment.trailingAnchor.constraint(equalTo: trailingAnchor),

            // topSegment constrained top, bottom and leading
            topSegment.topAnchor.constraint(equalTo: topAnchor),
            topSegment.bottomAnchor.constraint(equalTo: bottomAnchor),
            topSegment.leadingAnchor.constraint(equalTo: leadingAnchor),

            // activate topSegemnt width constraint
            startConstraint,

            ])
    }

    func showTopSegment() -> Void {
        // deactivate startConstraint
        startConstraint.isActive = false
        // activate endConstraint
        endConstraint.isActive = true
    }

}

protocol ATCSegmentDataSource {
    func numberOfSegmentsToShow() -> Int
}

class ATCStorySegmentsView: UIView {

    let theStackView: UIStackView = {
        let v = UIStackView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.axis = .horizontal
        v.alignment = .fill
        v.distribution = .fillEqually
        v.spacing = 4
        return v
    }()

    var segmentsArray: [Segment] = [Segment]()

    var delegate: ATCSegmentDataSource? {
        didSet {
            addSegments()
        }
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func commonInit() -> Void {
        addSubview(theStackView)

        NSLayoutConstraint.activate([

            // constrain stack view to all 4 sides
            theStackView.topAnchor.constraint(equalTo: topAnchor),
            theStackView.bottomAnchor.constraint(equalTo: bottomAnchor),
            theStackView.leadingAnchor.constraint(equalTo: leadingAnchor),
            theStackView.trailingAnchor.constraint(equalTo: trailingAnchor),

            ])
    }

    private func addSegments() {
        let numberOfSegment = delegate?.numberOfSegmentsToShow()
        guard let segmentQuantity = numberOfSegment else { return }

        // add desired number of Segment subviews to teh stack view
        for _ in 0..<segmentQuantity {
            let seg = Segment()
            seg.translatesAutoresizingMaskIntoConstraints = false
            theStackView.addArrangedSubview(seg)
            segmentsArray.append(seg)
        }
    }

    func startAnimation() -> Void {

        // this will animate changing the topSegment's width
        self.segmentsArray.first?.showTopSegment()
        UIView.animate(withDuration: 1.5, animations: {
            self.layoutIfNeeded()
        })

    }


}

class StoryViewController: UIViewController, ATCSegmentDataSource {

    let segmentContainerView: ATCStorySegmentsView = ATCStorySegmentsView()

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .red

        view.addSubview(segmentContainerView)

        segmentContainerView.translatesAutoresizingMaskIntoConstraints = false

        NSLayoutConstraint.activate([

            // constrain segmentContainerView to top (safe-area) + 20-pts "padding",
            segmentContainerView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 20.0),

            // leading and trailing with "padding" of 20-pts
            segmentContainerView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 20.0),
            segmentContainerView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -20.0),

            // constrain height to 10-pts
            segmentContainerView.heightAnchor.constraint(equalToConstant: 10.0),

            ])

        // set the delegate
        segmentContainerView.delegate = self

    }

    override func viewDidAppear(_ animated: Bool) {
        segmentContainerView.startAnimation()
    }

    func numberOfSegmentsToShow() -> Int {
        return 3
    }

}

<小时/>

结果(当 View 出现时，白色条以动画方式穿过灰色条):

有 5 段:

请注意，正如自动布局的设计目的一样，它还可以处理尺寸更改，例如当设备旋转时: