An empty snapshotView on iPhone 7/7plus

问题

My first question here:) Recently I update my Xcode to 8, and the resizableSnapshotView method doesn't work properly on some simulators. The snapshotView works well on all testing devices with iOS9/10 and simulators under iPhone6s, but it is empty on iPhone7/7p simulators. I think 7/7p may need some authorities for accessing snapshot, but I have no idea what they are.

let cell = self.tableView.cellForRow(at: IndexPath(row: 0, section: 0)) as! CalendarCell     
var topFrame = cell.frame
topFrame.origin.y = tableView.contentOffset.y
topFrame.size.height -= tableView.contentOffset.y
topSnapshotView = tableView.resizableSnapshotView(from: topFrame, afterScreenUpdates: false, withCapInsets: UIEdgeInsets.zero)

回答1:

Use the following UIView extension to create a snapshot using CoreGraphics.

I can confirm this works on iPhone 7 simulator.

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
        }
    }
}

回答2:

Works in:

• Version 8.1 (8B62)
• Simulator Version 10.0 (SimulatorApp-700.14

Swift 3

import Foundation
import UIKit

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

    func snapshotImage() -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(bounds.size, isOpaque, contentScaleFactor)
        defer { UIGraphicsEndImageContext() }

        drawHierarchy(in: bounds, afterScreenUpdates: false)

        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

来源：https://stackoverflow.com/questions/39609530/an-empty-snapshotview-on-iphone-7-7plus