Question

我有一个班级

class ActivitiesMainPageController: UICollectionViewController      ,UIImagePickerControllerDelegate, UINavigationControllerDelegate{

 override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

    switch indexPath.item {

    case 0 :
        let takePictureInstance = takePictures()
        takePictureInstance.presentCamera()
    }

}

takePictures（）是自定义类

class takePictures: UIViewController, UIImagePickerControllerDelegate, UIAlertViewDelegate, UINavigationControllerDelegate
{
   var imagePicker: UIImagePickerController! = UIImagePickerController()
  func presentCamera()
    {

    if UIImagePickerController.isSourceTypeAvailable(UIImagePickerControllerSourceType.camera)
    {

        let objViewController =  UIApplication.shared.keyWindow?.rootViewController

        imagePicker =  UIImagePickerController()
        imagePicker.delegate = self
        imagePicker.allowsEditing = false
        imagePicker.sourceType = UIImagePickerControllerSourceType.camera
        objViewController?.present(imagePicker,animated: true,completion: nil)
   }
    else
    {
        // error msg
        print ("error displaying Camera")
         noCamera()
    }
}



  func imagePickerController(_ picker: UIImagePickerController, didFinishPickingImage image: UIImage, editingInfo: [String : AnyObject]?) {

    print(self.Tag + "image picker controller")

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

didfinishpickingimage永远不会被触发。我没有看到印刷声明。在阅读了SO ere,后，我想我没有正确地做代理。你能帮忙吗？

Answer 1

为什么要从takePictures类呈现UIImagePicker（应该是TakePictures）？我认为问题源于此问题，因为您当前所处的视图控制器不是呈现选择器的视图控制器。如果您将presentCamera()函数拉出并将其放入ActivitiesMainPageController并将其指定为＆lt; - 作为代理，并将方法签名切换为正确的：

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any])

你应该有更好的运气。

Answer 2

问题出在您的ActivitiesMainPageController课程中。这是一个内存管理问题。您创建takePictures类的本地实例（FYI - 类名称应以大写字母开头），然后调用presentCamera方法。然后takePictureInstance变量立即超出范围。这意味着它没有更多的引用，并且它被取消分配。

因此，此时，图像选择器（弱）委托变为nil。这就是从不调用图像选择器委托方法的原因。

有两种方法可以解决这个问题：

强烈引用takePictures类中的ActivitiesMainPageController实例（使用属性而不是局部变量）。但是这有一个问题就是不知道何时发布实例。
在takePictures类中执行一个小技巧，它在创建时保留对自身的强引用，然后在图像选择器被解除后释放该强引用。

选项2可以像这样实现：

class takePictures: UIViewController, UIImagePickerControllerDelegate, UIAlertViewDelegate, UINavigationControllerDelegate
{
    var strongSelf: takePictures?
    var imagePicker: UIImagePickerController! = UIImagePickerController()

    func presentCamera()
    {
        if UIImagePickerController.isSourceTypeAvailable(UIImagePickerControllerSourceType.camera)
        {
            let objViewController =  UIApplication.shared.keyWindow?.rootViewController

            imagePicker =  UIImagePickerController()
            imagePicker.delegate = self
            imagePicker.allowsEditing = false
            imagePicker.sourceType = UIImagePickerControllerSourceType.camera
            objViewController?.present(imagePicker,animated: true,completion: nil)
            strongSelf = self // keep me around
        }
        else
        {
            // error msg
            print ("error displaying Camera")
            noCamera()
        }
    }

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingImage image: UIImage, editingInfo: [String : AnyObject]?) {
        print(self.Tag + "image picker controller")

        self.dismiss(animated: true, completion: nil)
        strongSelf = nil // let me go
    }
}

didFinishPickingImage不会被触发

2 个答案: