Question

我有一个“屏幕外” UIView层次结构，我想在屏幕的不同位置进行渲染。此外，应该只显示该视图层次结构的一部分，并应反映对该层次结构所做的所有更改。

困难：

UIView方法drawHierarchy(in:afterScreenUpdates:)总是调用draw(_ rect:)，因此如果要将所有更改合并到视图层次结构中，则对于大型层次结构效率很低。您必须在每次屏幕更新时重新绘制它，或者观察所有视图的所有更改的属性。 Draw view hierarchy documentation
UIView方法snapshotView(afterScreenUpdates:)也无济于事，因为如果此层次结构处于“屏幕外”状态，我还没有找到获取正确视图层次结构图形的方法。 Snapshot view documentation

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

在下面您可以看到我的想法的直观表示：

Answer 1

这就是我要做的事情。首先，我将复制您要复制的视图。我为此写了一个扩展：

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，我将遮盖重复的视图，以仅获取所需的特定部分

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

最后，我将使用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，但是如果需要，您可以更改它以将更多内容从一个视图复制到另一个视图。

祝你好运，让我知道怎么回事：）

Answer 2

我要复制想要显示的内容，并根据需要裁剪。

比方说，我有一个ContentViewController，它带有我想复制的视图层次结构。我将封装可以对ContentViewModel内部的层次结构进行的所有更改。像这样：

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

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

使用ClippingView（或简单的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，我将裁剪我的内容的每个实例，并在每次发生事情时更新它们：

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) }
    }
}

这种情况在您的情况下可行吗？

高效的屏幕外UIView渲染和镜像

2 个答案: