使用completionSelector和completionTarget与UIImageWriteToSavedPhotosAlbum
我试图找出一个办法让我的iOS应用程序保存到相机胶卷的屏幕截图，然后popup警告告诉用户屏幕截图已成功保存。
我认为这样做的唯一方法就是使用某种forms的if / else循环（正如您在下面的伪代码注释中看到的那样），但是我想不出任何语法可以使用UIKit的UIImageWriteToSavedPhotosAlbum函数。 我遇到了一些build议，说在Apple的开发网站上使用completionSelector和completionTarget，但我真的不明白如何使用它们，或者我的代码中completionSelector和completionTarget应该使用什么特定的字典。 我对Swift比较陌生。
有人可以解释他们如何工作，以及如何find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) }
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 } }
下面是一个工作示例，用于在SWIFT 3.0中的相机卷中保存当前视图的屏幕截图
@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) }
}
@敢于检查错误的解决scheme不适合我（Swift 2.0）。
这个微小的修改确实奏效：
func image(image: UIImage, didFinishSavingWithError: NSError?, contextInfo:UnsafePointer<Void>) { if didFinishSavingWithError != nil { Helper.showNotifierInfo(DefaultTextFailed) } else { Helper.showNotifierInfo(DefaultTextSaved) } }
另一个例子在迅速2.2
这个例子中的关键区别是具有callback函数的类必须从NSObject扩展 （@objc也可以）
func writeImage(){ let responder = WriteImageToFileResponder() responder.addCompletion{ print("completed") } let image = UIImage(color: .redColor(), size: CGSize(width: 100, height: 100))! UIImageWriteToSavedPhotosAlbum(image, responder, #selector(WriteImageToFileResponder.image(_:didFinishSavingWithError:contextInfo:)), nil) } class WriteImageToFileResponder: NSObject { var completion: (() -> Void)? func image(image: UIImage, didFinishSavingWithError error: NSError?, contextInfo: UnsafeMutablePointer<Void>) { print(error) completion?() } func addCompletion(completion: (() -> Void)? ) { self.completion = completion } }