Swift 3 / 为什么快照视图中的快照在 iPhone 7 Plus 模拟器中显示为空白？

Question

我正在使用以下代码来创建自定义菜单转换。我花了两个小时试图弄清楚为什么快照显示为空白（仅使用 iPhone 7 Plus 模拟器）。但是当我想为这个线程创建一个视频并将其制作成 gif 时，它在我的 iPhone 6S Plus 上运行。

更新：也适用于 iPhone 6S 模拟器。但在 7 Plus 中仍然没有。

import UIKit

class PresentMenuAnimator : NSObject {
}

extension PresentMenuAnimator : UIViewControllerAnimatedTransitioning {
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.6
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

        let fromVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from)
        let toVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)
        let containerView = transitionContext.containerView
        containerView.insertSubview((toVC?.view)!, belowSubview: (fromVC?.view)!)

        // replace main view with snapshot
        let snapshot = fromVC?.view.snapshotView(afterScreenUpdates: false)
        snapshot?.tag = MenuHelper.snapshotNumber
        snapshot?.isUserInteractionEnabled = false
        snapshot?.layer.shadowOpacity = 0.7
        containerView.insertSubview(snapshot!, aboveSubview: (toVC?.view)!)
        fromVC?.view.isHidden = true

        UIView.animate(
            withDuration: transitionDuration(using: transitionContext),
            animations: {
                snapshot!.center.x += UIScreen.main.bounds.width * MenuHelper.menuWidth
            },
            completion: { _ in
                fromVC?.view.isHidden = false
                transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
            }
        )
    }
}

iPhone 6S Plus（物理设备）iOS 10

iPhone 7 Plus（模拟器）iOS 10

为什么模拟器上的快照是空白的？

GitHub test project

Answer 1

替代解决方案，

添加这个UIView 扩展，

public extension UIView {
    public func snapshotImage() -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(bounds.size, isOpaque, 0)
        drawHierarchy(in: bounds, afterScreenUpdates: false)
        let snapshotImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return snapshotImage
    }

    public func snapshotView() -> UIView? {
        if let snapshotImage = snapshotImage() {
            return UIImageView(image: snapshotImage)
        } else {
            return nil
        }
    }
}

更新您的以下代码，

let snapshot = fromVC?.view.snapshotView(afterScreenUpdates: false)

与，

let snapshot = fromVC?.view.snapshotView()

Ref