我正在从 viewWillAppear 的 nib 加载自定义 View 类。加载 Nib 后，我将其添加为 subview ，然后应用一些约束，然后更新约束。那时我尝试向该 View 添加阴影，但没有显示任何阴影....

仅在某些上下文中，ViewController 具有包含 contentView 的 ScrollView 。 View 的所有内容都在这个 contentView 中。

这是我的代码:

View Controller

class MyViewController: UIViewController {

    @IBOutlet weak var contentView: UIView!

    var matches: [Match] = []
    var matchViews: [MatchDetailsView] = []

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        setMatches()
    }

    func setMatches() {

        // Match One
        let matchOneDetailsView = MatchDetailsView.instanceFromNib(match: matches.count > 0 ? matches[0] : nil, delegate: self, tag: 1)
        contentView.addSubview(matchOneDetailsView)
        matchOneDetailsView.translatesAutoresizingMaskIntoConstraints = false
        let matchOneLeadingConstraint = NSLayoutConstraint(item: matchOneDetailsView, attribute: .leading, relatedBy: .equal, toItem: contentView, attribute: .leading, multiplier: 1, constant: 16)
        let matchOneTrailingConstraint = NSLayoutConstraint(item: matchOneDetailsView, attribute: .trailing, relatedBy: .equal, toItem: contentView, attribute: .trailing, multiplier: 1, constant: -16)
        let matchOneTopConstraint = NSLayoutConstraint(item: matchOneDetailsView, attribute: .top, relatedBy: .equal, toItem: contentView, attribute: .top, multiplier: 1, constant: 32)

        // Match Two
        let matchTwoDetailsView = MatchDetailsView.instanceFromNib(match: matches.count > 1 ? matches[1] : nil, delegate: self, tag: 2)
        contentView.addSubview(matchTwoDetailsView)
        matchTwoDetailsView.translatesAutoresizingMaskIntoConstraints = false
        let matchTwoLeadingConstraint = NSLayoutConstraint(item: matchTwoDetailsView, attribute: .leading, relatedBy: .equal, toItem: contentView, attribute: .leading, multiplier: 1, constant: 16)
        let matchTwoTrailingConstraint = NSLayoutConstraint(item: matchTwoDetailsView, attribute: .trailing, relatedBy: .equal, toItem: contentView, attribute: .trailing, multiplier: 1, constant: -16)
        let matchTwoTopConstraint = NSLayoutConstraint(item: matchTwoDetailsView, attribute: .top, relatedBy: .equal, toItem: matchOneDetailsView, attribute: .bottom, multiplier: 1, constant: 32)

        // Match Three
        let matchThreeDetailsView = MatchDetailsView.instanceFromNib(match: matches.count > 2 ? matches[2] : nil, delegate: self, tag: 3)
        contentView.addSubview(matchThreeDetailsView)
        matchThreeDetailsView.translatesAutoresizingMaskIntoConstraints = false
        let matchThreeLeadingConstraint = NSLayoutConstraint(item: matchThreeDetailsView, attribute: .leading, relatedBy: .equal, toItem: contentView, attribute: .leading, multiplier: 1, constant: 16)
        let matchThreeTrailingConstraint = NSLayoutConstraint(item: matchThreeDetailsView, attribute: .trailing, relatedBy: .equal, toItem: contentView, attribute: .trailing, multiplier: 1, constant: -16)
        let matchThreeTopConstraint = NSLayoutConstraint(item: matchThreeDetailsView, attribute: .top, relatedBy: .equal, toItem: matchTwoDetailsView, attribute: .bottom, multiplier: 1, constant: 32)
        let matchThreeBottomConstraint = NSLayoutConstraint(item: matchThreeDetailsView, attribute: .bottom, relatedBy: .equal, toItem: contentView, attribute: .bottom, multiplier: 1, constant: -32)

        NSLayoutConstraint.activate([matchOneLeadingConstraint, matchOneTrailingConstraint, matchOneTopConstraint, matchTwoLeadingConstraint, matchTwoTrailingConstraint, matchTwoTopConstraint, matchThreeLeadingConstraint, matchThreeTrailingConstraint, matchThreeTopConstraint, matchThreeBottomConstraint])

        updateViewConstraints()

        matchViews.append(matchOneDetailsView)
        matchViews.append(matchTwoDetailsView)
        matchViews.append(matchThreeDetailsView)

        styleMatchViews()
    }


    func styleMatchViews() {
        for view in matchViews {
            view.addShadow(opacity: 0.25, yOffset: 0, xOffset: 0, radius: 5.0)
            view.roundCorners(withRadius: 5.0)
        }
    }
}

匹配详情 View

class MatchDetailsView: UIView {

        class func instanceFromNib(match: Match?, delegate: MatchDetailsViewDelegate, tag: Int) -> MatchDetailsView {

        let view = UINib(nibName: "MatchDetailsView", bundle: nil).instantiate(withOwner: MatchDetailsView(), options: nil)[0] as! MatchDetailsView
        view.translatesAutoresizingMaskIntoConstraints = false
        view.updateMatchContent()
        return view
    }
}

UIViewExtension

extension UIView {

/**
 Add Shadow

 Puts a Drop Shadow in the UIView
 */
func addShadow(opacity: Float, yOffset: Int, xOffset: Int, radius: CGFloat) {
        self.layer.masksToBounds = false
        self.layer.shadowColor = UIColor.black.cgColor
        self.layer.shadowOpacity = opacity
        self.layer.shadowOffset = CGSize(width: xOffset, height: yOffset)
        self.layer.shadowRadius = radius
        self.layer.shadowPath = UIBezierPath(rect: self.bounds).cgPath
    }
}

如果 MatchDetailsView 的 nib 文件将 'clipsToBounds' 设置为 false，为什么我的影子在页面加载时不显示？我是否缺少 layout 函数，即使它们看起来布局正确？

最佳答案

您正在将 .shadowPath 设置为 View 的边界...但此时的边界可能不是(可能不会)自动布局布局 View 后的边界.

对于“阴影 View ”，最好在 View 本身的 layoutSubviews() 中设置阴影。

您还应该在 viewDidLoad() 中添加和设置您的 subview viewWillAppear() 可能会被多次调用(取决于您的导航)，您将结束添加多个 subview 副本。

所以...

像这样更改您的 MatchDetailsView 类:

class MatchDetailsView: UIView {

    var opacity: CGFloat = 0.0
    var xOffset: CGFloat = 0.0
    var yOffset: CGFloat = 0.0

    // for the shadowRadius
    var sRadius: CGFloat = 0.0

    // for the cornerRadius
    var cRadius: CGFloat = 0.0

    override func layoutSubviews() {

        self.layer.masksToBounds = false

        self.layer.shadowColor = UIColor.black.cgColor
        self.layer.shadowOpacity = Float(opacity)
        self.layer.shadowOffset = CGSize(width: xOffset, height: yOffset)
        self.layer.shadowRadius = sRadius
        self.layer.shadowPath = UIBezierPath(rect: self.bounds).cgPath

        self.layer.cornerRadius = cRadius
    }

    class func instanceFromNib(match: Match?, delegate: MatchDetailsViewDelegate, tag: Int) -> MatchDetailsView {

        let view = UINib(nibName: "MatchDetailsView", bundle: nil).instantiate(withOwner: MatchDetailsView(), options: nil)[0] as! MatchDetailsView
        view.translatesAutoresizingMaskIntoConstraints = false
        view.updateMatchContent()
        return view
    }

}

然后，在你的 View Controller 中:

override func viewDidLoad() {
    super.viewDidLoad()
    setMatches()
}

func setMatches() {

    // Match One
    let matchOneDetailsView = MatchDetailsView.instanceFromNib(match: matches.count > 0 ? matches[0] : nil, delegate: self, tag: 1)
    contentView.addSubview(matchOneDetailsView)
    matchOneDetailsView.translatesAutoresizingMaskIntoConstraints = false
    let matchOneLeadingConstraint = NSLayoutConstraint(item: matchOneDetailsView, attribute: .leading, relatedBy: .equal, toItem: contentView, attribute: .leading, multiplier: 1, constant: 16)
    let matchOneTrailingConstraint = NSLayoutConstraint(item: matchOneDetailsView, attribute: .trailing, relatedBy: .equal, toItem: contentView, attribute: .trailing, multiplier: 1, constant: -16)
    let matchOneTopConstraint = NSLayoutConstraint(item: matchOneDetailsView, attribute: .top, relatedBy: .equal, toItem: contentView, attribute: .top, multiplier: 1, constant: 32)

    // Match Two
    let matchTwoDetailsView = MatchDetailsView.instanceFromNib(match: matches.count > 1 ? matches[1] : nil, delegate: self, tag: 2)
    contentView.addSubview(matchTwoDetailsView)
    matchTwoDetailsView.translatesAutoresizingMaskIntoConstraints = false
    let matchTwoLeadingConstraint = NSLayoutConstraint(item: matchTwoDetailsView, attribute: .leading, relatedBy: .equal, toItem: contentView, attribute: .leading, multiplier: 1, constant: 16)
    let matchTwoTrailingConstraint = NSLayoutConstraint(item: matchTwoDetailsView, attribute: .trailing, relatedBy: .equal, toItem: contentView, attribute: .trailing, multiplier: 1, constant: -16)
    let matchTwoTopConstraint = NSLayoutConstraint(item: matchTwoDetailsView, attribute: .top, relatedBy: .equal, toItem: matchOneDetailsView, attribute: .bottom, multiplier: 1, constant: 32)

    // Match Three
    let matchThreeDetailsView = MatchDetailsView.instanceFromNib(match: matches.count > 2 ? matches[2] : nil, delegate: self, tag: 3)
    contentView.addSubview(matchThreeDetailsView)
    matchThreeDetailsView.translatesAutoresizingMaskIntoConstraints = false
    let matchThreeLeadingConstraint = NSLayoutConstraint(item: matchThreeDetailsView, attribute: .leading, relatedBy: .equal, toItem: contentView, attribute: .leading, multiplier: 1, constant: 16)
    let matchThreeTrailingConstraint = NSLayoutConstraint(item: matchThreeDetailsView, attribute: .trailing, relatedBy: .equal, toItem: contentView, attribute: .trailing, multiplier: 1, constant: -16)
    let matchThreeTopConstraint = NSLayoutConstraint(item: matchThreeDetailsView, attribute: .top, relatedBy: .equal, toItem: matchTwoDetailsView, attribute: .bottom, multiplier: 1, constant: 32)
    let matchThreeBottomConstraint = NSLayoutConstraint(item: matchThreeDetailsView, attribute: .bottom, relatedBy: .equal, toItem: contentView, attribute: .bottom, multiplier: 1, constant: -32)

    NSLayoutConstraint.activate([matchOneLeadingConstraint, matchOneTrailingConstraint, matchOneTopConstraint, matchTwoLeadingConstraint, matchTwoTrailingConstraint, matchTwoTopConstraint, matchThreeLeadingConstraint, matchThreeTrailingConstraint, matchThreeTopConstraint, matchThreeBottomConstraint])

    matchViews.append(matchOneDetailsView)
    matchViews.append(matchTwoDetailsView)
    matchViews.append(matchThreeDetailsView)

    styleMatchViews()
}


func styleMatchViews() {
    for view in matchViews {
        view.opacity = 0.25
        view.yOffset = 0.0
        view.xOffset = 0.0
        view.sRadius = 5.0
        view.cRadius = 5.0
    }
}

关于ios - 将阴影应用于从 Nib 加载的 subview ，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/53733970/