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我有一个“屏幕外”的 UIView 层次结构，我想在屏幕的不同位置进行渲染。此外，应该可以只显示这个视图层次结构的一部分，并且应该反映对这个层次结构所做的所有更改。

困难：

  • 如果您想将所有更改合并到视图层次结构中，该UIView方法drawHierarchy(in:afterScreenUpdates:)总是调用并且因此对于大型层次结构非常低效。draw(_ rect:)您必须在每次屏幕更新时重新绘制它或观察所有视图的所有变化属性。绘制视图层次文档
  • 该UIView方法snapshotView(afterScreenUpdates:)也没有多大帮助，因为如果这个层次结构是“屏幕外”，我还没有找到一种方法来获得正确的视图层次结构图。快照视图文档

“屏幕外”：此视图层次结构的根视图不是应用程序 UI 的一部分。它没有超级视图。

您可以在下面看到我的想法的直观表示：

例子

4

2 回答 2

0

我会复制我希望显示的内容并根据需要对其进行裁剪。

假设我有一个ContentViewController带有我希望复制的视图层次结构。我会将所有可以对层次结构进行的更改封装在一个ContentViewModel. 就像是：

struct ContentViewModel {
    let actionTitle: String?
    let contentMessage: String?
    // ...
}

class ContentViewController: UIViewController {
    func display(_ viewModel: ContentViewModel) { /* ... */ }
}

使用ClippingView（或简单UIScrollView）：

class ClippingView: UIView {

    var contentOffset: CGPoint = .zero // a way to specify the part of the view you wish to display
    var contentFrame: CGRect = .zero // the actual size of the clipped view

    var clippedView: UIView?

    override init(frame: CGRect) {
        super.init(frame: frame)
        clipsToBounds = true
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        clippedView?.frame = contentFrame
        clippedView?.frame.origin = contentOffset
    }
}

还有一个视图控制器容器，我会裁剪我的内容的每个实例，并在每次发生某些事情时更新它们：

class ContainerViewController: UIViewController {

    let contentViewControllers: [ContentViewController] = // 3 in your case

    override func viewDidLoad() {
        super.viewDidLoad()
        contentViewControllers.forEach { viewController in
             addChil(viewController)
             let clippingView = ClippingView()
             clippingView.clippedView = viewController.view
             clippingView.contentOffset = // ...
             viewController.didMove(to: self)
        }
    }

    func somethingChange() {
        let newViewModel = ContentViewModel(...)
        contentViewControllers.forEach { $0.display(newViewModel) }
    }
}

这种情况是否适用于您的情况？

于 2019-02-25T18:27:35.507 回答
0

这就是我将如何去做。首先，我会复制您尝试复制的视图。我为此写了一个小扩展：

extension UIView {
    func duplicate<T: UIView>() -> T {
        return NSKeyedUnarchiver.unarchiveObject(with: NSKeyedArchiver.archivedData(withRootObject: self)) as! T
    }

    func copyProperties(fromView: UIView, recursive: Bool = true) {
        contentMode = fromView.contentMode
        tag = fromView.tag

        backgroundColor = fromView.backgroundColor
        tintColor = fromView.tintColor

        layer.cornerRadius = fromView.layer.cornerRadius
        layer.maskedCorners = fromView.layer.maskedCorners

        layer.borderColor = fromView.layer.borderColor
        layer.borderWidth = fromView.layer.borderWidth

        layer.shadowOpacity = fromView.layer.shadowOpacity
        layer.shadowRadius = fromView.layer.shadowRadius
        layer.shadowPath = fromView.layer.shadowPath
        layer.shadowColor = fromView.layer.shadowColor
        layer.shadowOffset = fromView.layer.shadowOffset

        clipsToBounds = fromView.clipsToBounds
        layer.masksToBounds = fromView.layer.masksToBounds
        mask = fromView.mask
        layer.mask = fromView.layer.mask

        alpha = fromView.alpha
        isHidden = fromView.isHidden
        if let gradientLayer = layer as? CAGradientLayer, let fromGradientLayer = fromView.layer as? CAGradientLayer {
            gradientLayer.colors = fromGradientLayer.colors
            gradientLayer.startPoint = fromGradientLayer.startPoint
            gradientLayer.endPoint = fromGradientLayer.endPoint
            gradientLayer.locations = fromGradientLayer.locations
            gradientLayer.type = fromGradientLayer.type
        }

        if let imgView = self as? UIImageView, let fromImgView = fromView as? UIImageView {
            imgView.tintColor = .clear
            imgView.image = fromImgView.image?.withRenderingMode(fromImgView.image?.renderingMode ?? .automatic)
            imgView.tintColor = fromImgView.tintColor
        }

        if let btn = self as? UIButton, let fromBtn = fromView as? UIButton {
            btn.setImage(fromBtn.image(for: fromBtn.state), for: fromBtn.state)
        }

        if let textField = self as? UITextField, let fromTextField = fromView as? UITextField {
            if let leftView = fromTextField.leftView {
                textField.leftView = leftView.duplicate()
                textField.leftView?.copyProperties(fromView: leftView)
            }

            if let rightView = fromTextField.rightView {
                textField.rightView = rightView.duplicate()
                textField.rightView?.copyProperties(fromView: rightView)
            }

            textField.attributedText = fromTextField.attributedText
            textField.attributedPlaceholder = fromTextField.attributedPlaceholder
        }

        if let lbl = self as? UILabel, let fromLbl = fromView as? UILabel {
            lbl.attributedText = fromLbl.attributedText
            lbl.textAlignment = fromLbl.textAlignment
            lbl.font = fromLbl.font
            lbl.bounds = fromLbl.bounds
        }

       if recursive {
            for (i, view) in subviews.enumerated() {
                if i >= fromView.subviews.count {
                    break
                }

                view.copyProperties(fromView: fromView.subviews[i])
            }
        }
    }
}

要使用此扩展程序，只需执行

let duplicateView = originalView.duplicate()
duplicateView.copyProperties(fromView: originalView)
parentView.addSubview(duplicateView)

然后我会屏蔽重复视图以仅获取您想要的特定部分

let mask = UIView(frame: CGRect(x: 0, y: 0, width: yourNewWidth, height: yourNewHeight))
mask.backgroundColor = .black
duplicateView.mask = mask

最后，我会使用 CGAffineTransform 将其缩放到您想要的任何大小

duplicateView.transform = CGAffineTransform(scaleX: xScale, y: yScale)

copyProperties 函数应该可以正常工作，但如果需要将更多内容从一个视图复制到另一个视图，您可以更改它。

祝你好运，让我知道情况如何:)

于 2019-02-24T21:50:32.883 回答