Swift 3与Xcode 8.3.3下UIImagePickerController选图报错如何解决？

Hey there, let's work through your problem step by step—since you're using Swift 3 with Xcode 8.3.3 and hitting two frustrating issues: the "Creating an image format with an unknown type is an error" warning, and a crash from unexpectedly found nil when assigning to self?.imgView.image.

首先解决「unexpectedly found nil」崩溃问题 #

This is the critical one causing your app to crash, and it means self.imgView is nil when you try to set its image. Here's how to fix it:

• Check your IBOutlet connection:

  • Open your Storyboard/XIB and make sure the imgView outlet is properly connected to your UIImageView. Look for the hollow circle next to the @IBOutlet declaration in your ViewController code—if it's hollow, the connection is missing. Double-check that the outlet name matches exactly between your code and the Storyboard element's "Referencing Outlets" section.

• Ensure imgView is initialized (if using code-only setup):
  If you're creating imgView programmatically instead of using Storyboards, make sure you've initialized it and added it to your view hierarchy before calling takePhoto. For example:

  override func viewDidLoad() {
      super.viewDidLoad()
      // Initialize and add imgView to the view
      imgView = UIImageView(frame: CGRect(x: 20, y: 20, width: 200, height: 200))
      view.addSubview(imgView)
  }
  

• Add a safety check in takePhoto:
  To avoid crashes even if something goes wrong, add a guard statement to verify imgView exists before assigning the image:

  func takePhoto(newImage: UIImage) {
      guard let imageView = self.imgView else {
          print("Error: imgView is nil! Check IBOutlet or initialization.")
          return
      }
      imageView.image = newImage
  }
  

解决「Creating an image format with an unknown type is an error」警告 #

This warning usually pops up when the selected image has an uncommon format (like HEIC, which had limited support in older Xcode versions) or corrupted EXIF data. Try these fixes:

• Convert the image to a standard format:
  In your UIImagePickerControllerDelegate method, convert the picked image to JPEG or PNG before passing it to takePhoto. This ensures the image uses a widely supported format:

  func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
      picker.dismiss(animated: true, completion: nil)
      
      guard let originalImage = info[UIImagePickerControllerOriginalImage] as? UIImage else {
          print("Failed to retrieve selected image")
          return
      }
      
      // Convert to JPEG to resolve format issues
      if let jpegData = UIImageJPEGRepresentation(originalImage, 0.8), let formattedImage = UIImage(data: jpegData) {
          takePhoto(newImage: formattedImage)
      } else {
          // Fallback to original if conversion fails
          takePhoto(newImage: originalImage)
      }
  }
  

• Fix image orientation issues:
  Some images have incorrect EXIF orientation data, which can trigger format warnings. Use this helper method to correct the image's orientation:

  func correctedOrientationImage(_ image: UIImage) -> UIImage {
      guard image.imageOrientation != .up else { return image }
      
      UIGraphicsBeginImageContextWithOptions(image.size, false, image.scale)
      image.draw(in: CGRect(origin: .zero, size: image.size))
      let correctedImage = UIGraphicsGetImageFromCurrentImageContext()
      UIGraphicsEndImageContext()
      
      return correctedImage ?? image
  }
  

  Then use it in your delegate method:

  let fixedImage = correctedOrientationImage(originalImage)
  takePhoto(newImage: fixedImage)
  

Final Quick Checks #

• Make sure your ViewController conforms to both UIImagePickerControllerDelegate and UINavigationControllerDelegate protocols.
• Verify that you've added the NSPhotoLibraryUsageDescription key to your Info.plist with a brief explanation of why you need photo library access (required for iOS 10+).

内容的提问来源于stack exchange，提问作者bibscy