将阴影应用于从笔尖加载的子视图

Question

我正在从位于 viewWillAppear 的笔尖加载自定义视图 class。加载笔尖后，我将其添加为子视图，然后应用一些约束，然后更新约束。那时我尝试向该视图添加阴影，但没有显示任何阴影....

只是为了某些上下文，ViewController 具有包含 contentView 的滚动视图。视图的所有内容都在这个 contentView 中。

这是我的代码：

ViewController

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)
        }
    }
}

MatchDetailsView

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 'clipsToBounds' 设置为 false，为什么我的影子在页面加载时不显示？我是否遗漏了一个 layout 功能，即使它们看起来布局正确？

Answer 1

您正在将 .shadowPath 设置为视图的边界...但此时的边界可能不是（可能不会）自动布局布局视图后的边界。

对于 "shadowed view"，最好在视图本身的layoutSubviews() 中设置阴影。

您还应该在 viewDidLoad() 中添加和设置您的子视图 viewWillAppear() 可能会被多次调用（取决于您的导航），您最终会添加多个子视图副本。

所以...

像这样更改您的 MatchDetailsView class：

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，在您的视图控制器中：

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
    }
}

将阴影应用于从笔尖加载的子视图

Applying a shadow to a subview loaded from nib

uiview

ios

nslayoutconstraint

swift