ios 10 对尚未渲染的视图进行快照会导致快照为空

Question

this question ask again 但我找不到 ios 10

if UIImagePickerController.isSourceTypeAvailable(UIImagePickerControllerSourceType.camera)
 {
            self.imagePicker.delegate = self
            self.imagePicker.sourceType = UIImagePickerControllerSourceType.camera;
            self.imagePicker.allowsEditing = false
            self.imagePicker.cameraCaptureMode = .photo
            //self.imagePicker.modalPresentationStyle = UIModalPresentationStyle.overCurrentContext
            self.present(self.imagePicker, animated: true, completion: nil)
            self.imagePicked.isUserInteractionEnabled = true

 }
else
 {
            print("No Camera")
 }

对尚未渲染的视图进行快照会导致空白 快照。确保您的视图之前至少渲染过一次 屏幕更新后的快照或快照。

当我旋转相机并拍摄时，就会出现此错误。

Answer 1

自我解决方案像魅力一样为我工作 :-) 希望它对所有人都有帮助

DispatchQueue.global(qos: .userInitiated).async
{
     self.present(self.imagePicker, animated: true, completion: nil)

}

Answer 2

我收到了错误

此应用程序正在从后台线程修改自动布局引擎，这可能导致引擎损坏和奇怪的崩溃...

使用 DispatchQueue.main.async 代替对我有用。

Answer 3

此行为不限于 UIImagePickerController。下面是一个 UIViewController 的示例，它以模态方式呈现另一个 UIViewController。在第二个 UIViewController 中，启动 Safari 以显示 URL，从而触发相同的错误消息，“Cannot snapshot view (>) with afterScreenUpdates:NO, because the view is not in a window. Use afterScreenUpdates:YES.”

我还没有找到任何抑制消息的方法，但在我的应用程序中它没有害处。我认为这里发生的情况是，一些 Apple 代码正在拍摄应用程序视图层次结构的快照，但在拍摄快照之前尚未呈现键盘（由单独的 UIWIndow 拥有）。

/* Generates the error message:

 Cannot snapshot view (<UIKeyboardImpl: 0x7f82ded12ea0; frame = (0 0; 414 271); layer = <CALayer: 0x610000035e20>>) with afterScreenUpdates:NO, because the view is not in a window. Use afterScreenUpdates:YES.

 ... after the "Now Tap Me, For Glory!" label is clicked
*/

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let input = UITextField()
        input.placeholder = "Tap here first -- to bring up keyboard"
        input.frame = CGRect(x: 10, y: 50, width: 300, height: 20)
        view.addSubview(input)

        let button = UIButton()
        button.setTitleColor(UIColor.blue, for: .normal)
        button.setTitle("Then tap here", for: .normal)
        button.addTarget(self,
                         action: #selector(buttonPushed),
                         for: .touchUpInside)
        button.frame = CGRect(x: 10, y: 80, width: 200, height: 20)
        view.addSubview(button)
    }

    func buttonPushed() {
        let modalVC = ModalViewController()
        present(modalVC, animated: true, completion: nil)
    }
}

class ModalViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.white
        let label = UILabel()
        label.text = "Now Tap Me, For Glory!"
        label.frame = CGRect(x: 10, y: 50, width: 300, height: 20)
        view.addSubview(label)
        label.isUserInteractionEnabled = true
        label.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(labelTapped)))
    }

    func labelTapped() {
        UIApplication.shared.open(URL(string: "http://planetbeagle.com")!, options: [:], completionHandler: { _ in
                self.dismiss(animated: true, completion: nil) })
    }
}