使用completionSelector和completionTarget与UIImageWriteToSavedPhotosAlbum

Question

我正试图想办法让我的iOS应用程序将屏幕截图保存到相机胶卷,然后弹出警告,告诉用户屏幕截图已成功保存.

我能想到的唯一方法是使用某种形式的if/else循环(正如你在下面我的伪代码注释中看到的那样),但是我想不出任何与UIImageWriteToSavedPhotosAlbumUIKit函数一起使用的语法.我遇到建议,说使用completionSelector和completionTarget苹果的开发网站,但我真的不明白如何使用它们,或者我应该用什么样的具体措辞为completionSelector,并completionTarget在我的代码.我对Swift比较陌生.

有人可以解释它们是如何工作的,以及如何找到在我的代码中使用它们的语法？

func screenshotMethod()
{
    UIGraphicsBeginImageContextWithOptions(HighchartsView.scrollView.contentSize, false, 0);
    view.layer.renderInContext(UIGraphicsGetCurrentContext())
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
    //if saved to Camera Roll
    //            {
    //              confirmScreenshot()
    //            }
    //        
    //else 
    //        {
    //            exit code/stop 
    //        }


}


func confirmScreenshot()
{
    let alertController = UIAlertController(title: "Success", message: "This chart has been successfully saved to your Camera Roll.", preferredStyle: .Alert)
    let defaultAction = UIAlertAction(title: "OK", style: .Default, handler: nil)
    alertController.addAction(defaultAction)

    presentViewController(alertController, animated: true, completion: nil)
}

Answer 1

import UIKit

class ViewController: UIViewController {

   @IBAction func buttonPressed(sender: AnyObject) {
      presentImagePickerController()
   }

}

extension ViewController: UIImagePickerControllerDelegate, UINavigationControllerDelegate {

   func presentImagePickerController() {
      let imagePickerController = UIImagePickerController()
      imagePickerController.delegate = self
      imagePickerController.sourceType = .PhotoLibrary
      imagePickerController.allowsEditing = false

      presentViewController(imagePickerController, animated: true, completion: nil)
   }

   func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage, editingInfo: [String : AnyObject]?) {
      UIImageWriteToSavedPhotosAlbum(image, self, "image:didFinishSavingWithError:contextInfo:", nil)
   }

   func imagePickerControllerDidCancel(picker: UIImagePickerController) {
      self.dismissViewControllerAnimated(true, completion: nil)
   }

   func image(image: UIImage, didFinishSavingWithError error: NSError?, contextInfo:UnsafePointer<Void>) {
      guard error == nil else {
         //Error saving image
         return
      }
      //Image saved successfully
   }

}

Answer 2

以下是在SWIFT 3.0中保存相机胶卷中当前视图的屏幕截图的工作示例

 @IBAction func saveScreenshot(_ sender: Any) {

    //Create the UIImage
    UIGraphicsBeginImageContextWithOptions(editorView.frame.size, false, UIScreen.main.scale)

    //  UIGraphicsBeginImageContext(myTextView.frame.size)
    editorView.layer.render(in: UIGraphicsGetCurrentContext()!)
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    UIImageWriteToSavedPhotosAlbum(image!, self, #selector(TextEditorViewController.image(_:didFinishSavingWithError:contextInfo:)), nil)

}

func image(_ image: UIImage, didFinishSavingWithError error: NSError?, contextInfo: UnsafeRawPointer) {
if let error = error {
    // we got back an error!
    let ac = UIAlertController(title: "Save error", message: error.localizedDescription, preferredStyle: .alert)
    ac.addAction(UIAlertAction(title: "OK", style: .default))
    present(ac, animated: true)
} else {
    let ac = UIAlertController(title: "Saved!", message: "Your image has been saved to your photos.", preferredStyle: .alert)
    ac.addAction(UIAlertAction(title: "OK", style: .default))
    present(ac, animated: true)
}

}