高效的屏幕外UIView渲染和鏡像

Question

我有一個“屏幕外”的UIView層次結構，我希望在屏幕的不同位置進行渲染。 此外，應該可以僅顯示此視圖層次結構的一部分，並且應該反映對此層次結構所做的所有更改。

困難：

• UIView方法drawHierarchy(in:afterScreenUpdates:)總是調用draw(_ rect:) ，因此如果要將所有更改合並到視圖層次結構中，則對於大型層次結構效率非常低。 您必須在每次屏幕更新時重繪它或觀察所有視圖的所有更改屬性。 繪制視圖層次結構文檔
• UIView方法snapshotView(afterScreenUpdates:)也沒有多大幫助，因為如果這個層次結構是“屏幕外”，我還沒有找到一種方法來獲得正確的視圖層次結構圖。 快照視圖文檔

“屏幕外”：此視圖層次結構的根視圖不是應用程序UI的一部分。 它沒有超級視圖。

您可以在下面看到我的想法的直觀表示：

Answer 1

這是我將如何去做。 首先，我會復制您嘗試復制的視圖。 我為此寫了一點擴展：

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])
            }
        }
    }
}

要使用此擴展，只需這樣做

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

然后我會屏蔽重復的視圖，只獲得你想要的特定部分

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

最后，我會使用CGAffineTransform將其縮放到您想要的任何大小

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

copyProperties函數應該可以正常工作，但如果需要可以將其更改為從一個視圖復制到另一個視圖。

祝你好運，讓我知道它是怎么回事:)

Answer 2

我會復制我想要顯示的內容並根據需要裁剪它。

假設我有一個ContentViewController ，它帶有我希望復制的視圖層次結構。 我將封裝可以對ContentViewModel的層次結構進行的所有更改。 就像是：

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

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

使用ClippingView （或簡單的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
    }
}

和一個視圖控制器容器，我會裁剪我的內容的每個實例，並在每次發生時更新所有內容：

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) }
    }
} 

這種情況可以適用於您的情況嗎？