Ios 未调用UIImagePickerControllerDelegate函数

我有一个类，我在其中调用

UIImagePickerController

来选择一个图像并返回它，这样我就可以在代码中的其他地方使用它

现在我设置了委托并实现了所需的必要函数，但是没有调用委托函数

我的代码中存在问题的部分：

import UIKit

typealias PhotoTakingHelperCallback = (UIImage? -> Void)

class PhotoTakingHelper: NSObject
{

    weak var viewController:UIViewController!
    var callback: PhotoTakingHelperCallback
    var imagePickerController: UIImagePickerController?

    init(viewController:UIViewController , callback:PhotoTakingHelperCallback) {

        self.viewController = viewController

        self.callback = callback
        super.init()
        showPhotoSourceSelection()
    }


    func showPhotoSourceSelection() {
        let alertController = UIAlertController(title: nil, message: "Where do you want to get your picture from?", preferredStyle: .ActionSheet)

        let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel, handler: nil)

        alertController.addAction(cancelAction)

        let photoLibraryAction = UIAlertAction(title: "Photo from Library", style: .Default) { (action) -> Void in
            self.showImagePickerController(.PhotoLibrary)
        }

        alertController.addAction(photoLibraryAction)

        if (UIImagePickerController.isCameraDeviceAvailable(.Rear) ) {
            let cameraAction = UIAlertAction(title: "Photo from Camera", style: .Default, handler: { (action) -> Void in
                self.showImagePickerController(.Camera)
            })

            alertController.addAction(cameraAction)
        }

        viewController.presentViewController(alertController, animated: true, completion: nil)

    }

    func showImagePickerController(sourceType: UIImagePickerControllerSourceType) {
        imagePickerController = UIImagePickerController()
        imagePickerController!.delegate = self
        imagePickerController!.sourceType = sourceType

        print("Set the delegate \(imagePickerController?.delegate?.isMemberOfClass(PhotoTakingHelper))")

        self.viewController.presentViewController(imagePickerController!, animated: true, completion: nil)
    }

}


extension PhotoTakingHelper: UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
        print("HELLO?")
    }

    func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage!, editingInfo: [NSObject : AnyObject]!) {

        viewController.dismissViewControllerAnimated(false, completion: nil)
        print("calling the callback now " )

        callback(image)

        print("Finished calling the callback")
    }


}

我检查了很多，但没有一个解决了这个问题

我意识到没有一个委托方法被调用，因为当我在模拟器上运行程序并在照片库中选择图像时，控制台只打印图像

将委托设置为可选（true）

---

您正在创建一个

PhotoTakingHelper

，但没有保留对它的引用。也就是说，你在做这样的事情：

// In your view controller

@IBAction func pickImageButtonWasTapped() {
    _ = PhotoTakingHelper(viewController: self) { image in
        print("Callback!")
    }
}

// In your view controller

var helper: PhotoTakingHelper?

@IBAction func pickImageButtonWasTapped() {
    helper = PhotoTakingHelper(viewController: self) { image in
       print("Callback!")
    }
}

// In PhotoTakingHelper

var me: PhotoTakingHelper?

init(viewController:UIViewController , callback:PhotoTakingHelperCallback) {
    self.viewController = viewController
    self.callback = callback
    super.init()
    me = self
    showPhotoSourceSelection()
}

UIImagePickerController

只保留对其委托的弱引用，这不足以使其保持活动状态，因此必须保留对它的强引用。可以通过将辅助对象存储在视图控制器的实例变量中来实现，如下所示：

// In your view controller

@IBAction func pickImageButtonWasTapped() {
    _ = PhotoTakingHelper(viewController: self) { image in
        print("Callback!")
    }
}

// In your view controller

var helper: PhotoTakingHelper?

@IBAction func pickImageButtonWasTapped() {
    helper = PhotoTakingHelper(viewController: self) { image in
       print("Callback!")
    }
}

// In PhotoTakingHelper

var me: PhotoTakingHelper?

init(viewController:UIViewController , callback:PhotoTakingHelperCallback) {
    self.viewController = viewController
    self.callback = callback
    super.init()
    me = self
    showPhotoSourceSelection()
}

或者，您可以让助手保留对自身的引用，如下所示：

// In your view controller

@IBAction func pickImageButtonWasTapped() {
    _ = PhotoTakingHelper(viewController: self) { image in
        print("Callback!")
    }
}

// In your view controller

var helper: PhotoTakingHelper?

@IBAction func pickImageButtonWasTapped() {
    helper = PhotoTakingHelper(viewController: self) { image in
       print("Callback!")
    }
}

// In PhotoTakingHelper

var me: PhotoTakingHelper?

init(viewController:UIViewController , callback:PhotoTakingHelperCallback) {
    self.viewController = viewController
    self.callback = callback
    super.init()
    me = self
    showPhotoSourceSelection()
}

然后，在完成图像选取器时，需要将引用设置为nil，以便释放辅助对象：

extension PhotoTakingHelper: UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
        viewController.dismissViewControllerAnimated(false, completion: nil)
        callback(info[UIImagePickerControllerOriginalImage] as? UIImage)
        me = nil
    }

    func imagePickerControllerDidCancel(picker: UIImagePickerController) {
        viewController.dismissViewControllerAnimated(false, completion: nil)
        me = nil
    }

}

---

您正在创建一个

PhotoTakingHelper

，但没有保留对它的引用。也就是说，你在做这样的事情：

// In your view controller

@IBAction func pickImageButtonWasTapped() {
    _ = PhotoTakingHelper(viewController: self) { image in
        print("Callback!")
    }
}

// In your view controller

var helper: PhotoTakingHelper?

@IBAction func pickImageButtonWasTapped() {
    helper = PhotoTakingHelper(viewController: self) { image in
       print("Callback!")
    }
}

// In PhotoTakingHelper

var me: PhotoTakingHelper?

init(viewController:UIViewController , callback:PhotoTakingHelperCallback) {
    self.viewController = viewController
    self.callback = callback
    super.init()
    me = self
    showPhotoSourceSelection()
}

UIImagePickerController

只保留对其委托的弱引用，这不足以使其保持活动状态，因此必须保留对它的强引用。可以通过将辅助对象存储在视图控制器的实例变量中来实现，如下所示：

// In your view controller

@IBAction func pickImageButtonWasTapped() {
    _ = PhotoTakingHelper(viewController: self) { image in
        print("Callback!")
    }
}

// In your view controller

var helper: PhotoTakingHelper?

@IBAction func pickImageButtonWasTapped() {
    helper = PhotoTakingHelper(viewController: self) { image in
       print("Callback!")
    }
}

// In PhotoTakingHelper

var me: PhotoTakingHelper?

init(viewController:UIViewController , callback:PhotoTakingHelperCallback) {
    self.viewController = viewController
    self.callback = callback
    super.init()
    me = self
    showPhotoSourceSelection()
}

或者，您可以让助手保留对自身的引用，如下所示：

// In your view controller

@IBAction func pickImageButtonWasTapped() {
    _ = PhotoTakingHelper(viewController: self) { image in
        print("Callback!")
    }
}

// In your view controller

var helper: PhotoTakingHelper?

@IBAction func pickImageButtonWasTapped() {
    helper = PhotoTakingHelper(viewController: self) { image in
       print("Callback!")
    }
}

// In PhotoTakingHelper

var me: PhotoTakingHelper?

init(viewController:UIViewController , callback:PhotoTakingHelperCallback) {
    self.viewController = viewController
    self.callback = callback
    super.init()
    me = self
    showPhotoSourceSelection()
}

然后，在完成图像选取器时，需要将引用设置为nil，以便释放辅助对象：

extension PhotoTakingHelper: UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
        viewController.dismissViewControllerAnimated(false, completion: nil)
        callback(info[UIImagePickerControllerOriginalImage] as? UIImage)
        me = nil
    }

    func imagePickerControllerDidCancel(picker: UIImagePickerController) {
        viewController.dismissViewControllerAnimated(false, completion: nil)
        me = nil
    }

}

---

我想你的imagePickerController在委托方法调用之前就发布了…试着让它成为全局的…我的意思是声明为propertyyes，但我在代码示例中没有它，我现在添加它以防止混淆我想你的imagePickerController是在委托方法调用之前发布的…只是试着使其全局化…我的意思是声明为propertyyes我有，但我在代码示例中没有，我现在添加它以防混淆Hey@rob，尚未测试代码，但我想知道您是否可以向我发送任何链接，进一步解释为什么代理具有弱引用和整个强/弱引用，因为我发现它确实令人困惑！谢谢我也有同样的问题。通过将PhotoTakingHelper设置为我的视图控制器的类属性，修复了此问题。谢谢@robmayoffHey@rob，我还没有测试代码，但是我想知道你是否可以给我发送任何链接，进一步解释为什么代理有一个弱引用和整个强/弱引用，因为我发现它真的很混乱！谢谢我也有同样的问题。通过将PhotoTakingHelper设置为我的视图控制器的类属性，修复了此问题。谢谢@robmayoff