iOS14中的UIImagePickerController和PHPickerViewController图像选择空白

Question

在过去的几个版本的iOS上都可以工作，但在14上不能工作，我花了5天时间在谷歌上搜索。

每当我从图库中添加图像时，用于选择图像的弹出窗口都是空白的。

我已经尝试过UIImagePickerController(在iOS13及更低版本下运行良好)和新的PHPickerViewController。

在iOS14之前，用户单击一个栏按钮来“添加图像”，弹出窗口要求从图库中进行选择，然后向选取器显示图库中的图像。

我已经为UIImagePickerController设置了Info.plist“隐私-图片库使用说明”，我知道PHPickerViewController不需要烫发，因为它会为你获取图像。

我也经常看到这些紫色的警告，上面写着"xxxx只能在主线程中使用“，这在新的Xcode之前从未见过。

任何帮助都将不胜感激。运行Xcode12.0.1 (12A7300)，模拟器运行iOS14。

亚当

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class AddCustomExerciseViewController: UIViewController, UITextViewDelegate, UINavigationControllerDelegate, GADBannerViewDelegate, UIImagePickerControllerDelegate, PHPickerViewControllerDelegate{

let alert = UIAlertController(title: "Choose Image", message: nil, preferredStyle: .actionSheet)
        alert.addAction(UIAlertAction(title: "Gallery", style: .default, handler: { _ in self.openGallery() }))
        alert.addAction(UIAlertAction.init(title: "Cancel", style: .cancel, handler: nil))
        self.present(alert, animated: true, completion: nil)

func openGallery()
{
    let photoAuthorizationStatus = PHPhotoLibrary.authorizationStatus()
        switch photoAuthorizationStatus {
        case .authorized:
            self.showGallery()
            print("Access is granted by user")
        case .notDetermined:
            PHPhotoLibrary.requestAuthorization({
                (newStatus) in
                print("status is \(newStatus)")
                if newStatus ==  PHAuthorizationStatus.authorized {
                    self.showGallery()
                    print("success")
                }
            })
            print("It is not determined until now")
        case .restricted:
            // same same
            print("User do not have access to photo album.")
        case .denied:
            // same same
            print("User has denied the permission.")
        case .limited:
            // same same
            print("User has denied the permission.")
        }
}

func showGallery()
{
    if #available(iOS 14, *)
    {
        var configuration = PHPickerConfiguration()
        configuration.filter = .images
        configuration.selectionLimit = 0
        let picker = PHPickerViewController(configuration: configuration)
        picker.delegate = self
        self.present(picker, animated: true, completion: nil)
    }
    else
    {
                
        if UIImagePickerController.isSourceTypeAvailable(UIImagePickerController.SourceType.photoLibrary){
            let imagePicker = UIImagePickerController()
            imagePicker.delegate = self
            imagePicker.allowsEditing = false
            imagePicker.sourceType = UIImagePickerController.SourceType.photoLibrary
            self.present(imagePicker, animated: true, completion: nil)
        }
        else
        {
            let alert  = UIAlertController(title: "Warning", message: "You don't have permission to access gallery.", preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
            self.present(alert, animated: true, completion: nil)
        }
    }
}
func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
    if let pickedImage = info[UIImagePickerControllerOriginalImage] as? UIImage {
        
        //get the file url
        if let fileUrl = info[UIImagePickerControllerImageURL] as? URL {
            print(fileUrl)
            print(fileUrl.lastPathComponent)
            let filePath = fileUrl.lastPathComponent
            
            if(filePath.hasSuffix("GIF")||filePath.hasSuffix("gif"))
            {
                //to change later to support gifs
                gifView.image = pickedImage
            }
            else
            {
                //to show the static image to users
                gifView.image = pickedImage
            }
            //for saving the file name to retrieve in local parse datastore
            imageNameToSave = fileUrl.lastPathComponent
        }
        //for saving the selected image
        imageToSave = pickedImage
    }
    picker.dismiss(animated: true, completion: nil)
}
@available(iOS 14, *)
func picker(_ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult])
{
   picker.dismiss(animated: true, completion: nil)
   for result in results
   {
      result.itemProvider.loadObject(ofClass: UIImage.self, completionHandler: { (object, error) in
         if let image = object as? UIImage {
            DispatchQueue.main.async {
               // Use UIImage
               print("Selected image: \(image)")
            }
         }
      })
   }
}  }

Answer 1

在iOS 14上，受限制的图像选择器权限对话框在一个单独的线程中打开，因此当授权返回时，您将需要在主线程上执行UI任务。

PHPhotoLibrary.requestAuthorization({
        (newStatus) in
    DispatchQueue.main.async {
        print("status is \(newStatus)")
        if newStatus ==  PHAuthorizationStatus.authorized {
            self.showGallery()
            print("success")
        }
    }
})

Answer 2

如果这对其他人有帮助的话，我发现编辑滚动视图外观代理背景会导致UIImagePickerController和PHPickerViewController中都有一个bug，导致它们无法在iOS 14和更高版本中显示图像。我已经编辑了滚动视图背景代理，因为它即使在灯光模式下也是黑色的。经过几个小时的谷歌搜索和测试，我发现删除scrollview代理上的外观背景修改可以让图像选择器按预期工作。我向苹果提交了一份错误报告。导致错误的代码行是：

UIScrollView.appearance().backgroundColor = .systemBackground