每次在UIImagePickerController()的dismiss()之后调用viewDidLoad()

// 在模态视图控制器中定义代理协议
protocol ImagePickerDelegate: class {
    func imagePickerDidDismiss()
}

class ImagePickerViewController: UIViewController {
    weak var delegate: ImagePickerDelegate?

    // 在dismiss()之后调用代理方法
    func dismissImagePicker() {
        dismiss(animated: true) {
            self.delegate?.imagePickerDidDismiss()
        }
    }
}

class MainViewController: UIViewController, ImagePickerDelegate {
    // 在MainViewController中实现代理方法
    func imagePickerDidDismiss() {
        // 在dismiss()之后执行相应操作
        viewDidLoad()
    }

    // 弹出模态视图控制器
    func presentImagePicker() {
        let imagePicker = ImagePickerViewController()
        imagePicker.delegate = self
        present(imagePicker, animated: true, completion: nil)
    }
}

class ImagePickerViewController: UIViewController {
    var dismissCompletion: (() -> Void)?

    // 在dismiss()之后调用闭包回调
    func dismissImagePicker() {
        dismiss(animated: true) {
            self.dismissCompletion?()
        }
    }
}

class MainViewController: UIViewController {
    // 弹出模态视图控制器
    func presentImagePicker() {
        let imagePicker = ImagePickerViewController()
        imagePicker.dismissCompletion = {
            // 在dismiss()之后执行相应操作
            self.viewDidLoad()
        }
        present(imagePicker, animated: true, completion: nil)
    }
}