未调用 UIImagePickerController 委托

Question

使用下面的代码打开相机但无法调用选择器委托方法。 我没有收到错误消息。

import Foundation
import UIKit
import MobileCoreServices

class RecVidController: UIViewController {

    override func viewDidAppear(_ animated: Bool) {
        RecVidController.startRecord(delegate: self, sourceType: .camera)
    }

    static func startRecord(delegate: UIViewController & UINavigationControllerDelegate & UIImagePickerControllerDelegate, sourceType: UIImagePickerController.SourceType) {
        guard UIImagePickerController.isSourceTypeAvailable(sourceType) else { return }

        let mediaUI = UIImagePickerController()
        mediaUI.sourceType = sourceType
        mediaUI.mediaTypes = [kUTTypeMovie as String]
        mediaUI.allowsEditing = true
        mediaUI.delegate = delegate
        delegate.present(mediaUI, animated: true, completion: nil)
    }

    @objc func video(_ videoPath: String, didFinishSavingWithError error: Error?, contextInfo info: AnyObject) {
        let title = (error == nil) ? "Success" : "Error"
        let message = (error == nil) ? "Video was saved" : "Video failed to save"

        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: UIAlertAction.Style.cancel, handler: nil))
        present(alert, animated: true, completion: nil)
    }

}

// MARK: - UIImagePickerControllerDelegate

extension RecVidController: UIImagePickerControllerDelegate {
    private func imagePickerController(_ picker: UIImagePickerController,
                                       didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {

        dismiss(animated: true, completion: nil)

        guard let mediaType = info[UIImagePickerController.InfoKey.mediaType] as? String,
            mediaType == (kUTTypeMovie as String),
            let url = info[UIImagePickerController.InfoKey.mediaURL] as? URL,
            UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(url.path)
            else { return }

        // Handle a movie capture
        UISaveVideoAtPathToSavedPhotosAlbum(url.path, self, #selector(video(_:didFinishSavingWithError:contextInfo:)), nil)
    }

}

// MARK: - UINavigationControllerDelegate

extension RecVidController: UINavigationControllerDelegate {
}

Answer 1

问题是这个声明：

private func imagePickerController(
    _ picker: UIImagePickerController,
    didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {

您已将此方法声明为private ，因此 Objective-C 无法知道它是否存在。 因此，它不能调用它。

基本上，Cocoa 会查看此方法是否已实现，发现它没有实现（因为您已将其隐藏），然后放弃。 没有明显的惩罚，因为这个委托方法是可选的，当它没有实现时，当用户完成它时，Cocoa 会为你关闭选择器。

所以只需删除private ，你应该很高兴。 这将委托方法暴露给 Objective-C，因此它将被调用。

_{（您不必说@objc将其公开给Objective-C，就像这是您自己的函数一样，因为您已经声明我们采用UIImagePickerControllerDelegate，这是一个Objective-C 协议。）}

Answer 2

当程序未调用委托方法时，我遇到了类似的问题。

该imagePicker.delegate = self不应在viewDidLoad中（）方法，但在打开画廊方法。 像这样：

func openGallery()
    {
        let imagePicker = UIImagePickerController()
        imagePicker.delegate = self

        imagePicker.sourceType = .photoLibrary

        self.present(imagePicker, animated: true, completion: nil)
   }