ios - UIImagePickerController 第一次打开时速度很慢，双击时除外

Question

我在使用 swift 的 iOS 9 上遇到了这种非常奇怪的行为，我有一个 tableViewCell，当点击它拍摄某物时，它会打开一个 imagePicker，当第一次点击单元格需要大约 10 秒才能打开选择器，但是当你点击它两次时它会立即打开...

picker的初始化代码如下

let certificateImagePicker = UIImagePickerController()
certificateImagePicker.delegate = self
certificateImagePicker.allowsEditing = false
certificateImagePicker.sourceType = .Camera
certificateImagePicker.modalPresentationStyle = .CurrentContext

呈现选择器的代码是presentViewController(certificateImagePicker, animated: false, completion: nil)

我现在不知道它是否相关，但在打开选择器后它会显示此错误消息

Snapshotting a view that has not been rendered results in an empty snapshot. Ensure your view has been rendered at least once before snapshotting or snapshot after screen updates.

Answer 1

我在第一次尝试呈现 UIImagePickerController 时遇到了类似的延迟。在我的案例中，在初始化父 UIViewController 时初始化它很有帮助，如下所示:

class ExampleViewController: UIViewController, UIImagePickerControllerDelegate {
  let imagePicker = UIImagePickerController()

  func presentImagePicker() {
    imagePicker.delegate = self
    imagePicker.allowsEditing = false
    imagePicker.sourceType = .camera
    imagePicker.modalPresentationStyle = .currentContext
    self.present(imagePicker, animated: false, completion: nil)
  }
}