ios - 无法使用 snapshotViewAfterScreenUpdates 在 iOS 上获取屏幕截图 : method of UIScreen

Question

我正在尝试在我的 iOS 应用程序中获取屏幕截图图像。屏幕截图必须包含屏幕上的所有内容，包括状态栏，因此 this 等解决方案对我不起作用。我尝试了以下方法:

override func viewDidLoad() {
    super.viewDidLoad()

    // Wait for one second before taking the screenshot.
    Timer.scheduledTimer(withTimeInterval: 1, repeats: false) { timer in
        // Get a view containing the screenshot, shrink it a little, and show it.
        let view = UIScreen.main.snapshotView(afterScreenUpdates: false)
        view.frame = view.frame.insetBy(dx: 18, dy: 32)
        self.view.addSubview(view)

        // Get the screenshot image from the view, and save it to the photos album.
        UIGraphicsBeginImageContextWithOptions(UIScreen.main.bounds.size, false, 0)
        view.drawHierarchy(in: view.bounds, afterScreenUpdates: true)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        UIImageWriteToSavedPhotosAlbum(image!, nil, nil, nil)
    }
}

我在 iPhone 6 Plus 的 iOS 11.4.1 中运行了以上代码。截屏成功并显示在屏幕上，但保存到相册的图像是一片空白。我究竟做错了什么？捕获完整屏幕截图的正确方法是什么？

更新

根据 CZ54 的建议，我在调试 session 中检查了变量 image 的值，发现它完全是空白的，尽管它的大小是正确的。所以这里的关键问题是，我应该如何从 UIScreen.main.snapshotView() 方法返回的屏幕截图 View 中提取图像？

Answer 1

swift 4.1.1

   let deadlineTime = DispatchTime.now() + .seconds(1)
    // Wait for one second before taking the screenshot.
    DispatchQueue.main.asyncAfter(deadline: deadlineTime) {

        let view = UIScreen.main.snapshotView(afterScreenUpdates: false)
        view.frame = view.frame.insetBy(dx: 18, dy: 32)
        self.view.addSubview(view)

        // Get a view containing the screenshot, shrink it a little, and show it.
        UIGraphicsBeginImageContextWithOptions(self.view.frame.size, true, UIScreen.main.scale)
        //guard let context = UIGraphicsGetCurrentContext() else { return }
        //self.view.layer.render(in: context)
        self.view?.drawHierarchy(in:  self.view.bounds, afterScreenUpdates: true)
        guard let image = UIGraphicsGetImageFromCurrentImageContext() else { return }
        UIGraphicsEndImageContext()

        //Save it to the camera roll
        UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
    }