swift - Swift 5 UIImagePickerController is not getting called

Question

I have the most standard/out of the box code for calling the delegate function in UIImagePicker:

import Foundation import UIKit //import UIKit.UIImage

class FirstViewController:
      UIViewController
    , UIImagePickerControllerDelegate
{

    let imagePicker = UIImagePickerController()
    @IBOutlet weak var bigImageView: UIImageView!

    var newlyPickedImage: UIImage?

    override func viewDidLoad() {

        super.viewDidLoad()
        self.view.backgroundColor = Color.offWhiteLight

        let singleTap = UITapGestureRecognizer(target: self, action: #selector(onTapImageView))
        self.view.isUserInteractionEnabled = true
        self.view.addGestureRecognizer(singleTap)
    }

    @objc func onTapImageView(){
        DispatchQueue.main.async {
            self.imagePicker.allowsEditing = true
            self.imagePicker.sourceType = .photoLibrary
            self.present(self.imagePicker, animated: true, completion: nil)
        }
    }

    func imagePickerController(
         _ picker: UIImagePickerController
        , didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any])
    {
        print("assert enter function") /// not entered

        if let pickedImage = info[UIImagePickerController.InfoKey.originalImage] as? UIImage {
            self.bigImageView.image = pickedImage
            print("picked image: \(pickedImage)")
        }

        dismiss(animated: true, completion: nil)
    }
}

The issue is that func imagePickerController is not getting called. This is odd because in a different view the exact code does call func imagePickerController. I have also tried instantiating a global UIImagePickerController instance in the Appdelegate and referencing that, the call is still not called.

Answer 1

您似乎缺少UIImagePickerController. 用这个替换你onTapImageView的：

@objc func onTapImageView(){
    DispatchQueue.main.async {
        self.imagePicker.allowsEditing = true
        self.imagePicker.sourceType = .photoLibrary
        self.imagePicker.delegate = self
        self.present(self.imagePicker, animated: true, completion: nil)
    }
}

您还需要控制器确认以UINavigationControllerDelegate添加符合性，FirstViewController如下所示：

class FirstViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {