使用 Objective C 检测 imagePickerController 是否通过向下滑动手势关闭

Question

我试图检测通过滑动的 imagePickerController 何时通过向下滑动手势或通过取消关闭。

imagePicker 通过此方法加载（https://developer.apple.com/documentation/uikit/uiviewcontroller/1621380-presentviewcontroller）

[rootViewController presentViewController:picker animated:animated completion:NULL];

我们可以通过实现此方法简单地检测 pickerController 是否通过取消关闭（https://developer.apple.com/documentation/uikit/uiimagepickercontrollerdelegate/1619133-imagepickercontrollerdidcancel）

但是，我还想检测它是否通过向下滑动关闭（对于 iPhone X，...，我们可以向下滑动以关闭以模式方式显示的视图）

使用 Swift，我可以用以下代码检测它：

extension UIImagePickerController {
    open override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        // detecting
    }
}

我想知道在 Objective C 中是否有等效的方法（因为我正在从事的项目是用 Objective C 编写的）？或欢迎任何其他建议：D

Answer 1

首先，你不应该覆盖viewDidDisappear:（也不应该在 Objective-C 的类别中重写）。覆盖扩展/类别中的某些内容的结果是未定义的行为 - 它可能有效，也可能无效。永远不应该依赖它。

相反，将图像选择器的委托分配presentationController给某个类，然后让该类实现该presentationControllerDidDismiss:方法。当用户在所有动画完成后成功关闭图像选择器时，将调用此方法。（并请注意，这不是如果以编程方式关闭图像选择器，则

这是一个简短的示例，涵盖了关闭图像选择器的所有情况，而无需viewDidDisappear:在扩展程序或类别中进行覆盖：

@interface ViewController() <UIAdaptivePresentationControllerDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate>

@end

@implementation ViewController

- (IBAction)showImagePicker {
    UIImagePickerController *imagePicker = [UIImagePickerController new];
    imagePicker.delegate = self;
    imagePicker.presentationController.delegate = self;
    [self presentViewController:imagePicker animated:YES completion:nil];
}

#pragma mark - UIAdaptivePresentationControllerDelegate

- (void)presentationControllerWillDismiss:(UIPresentationController *)presentationController {
    NSLog(@"The user began to swipe down to dismiss.");
}

- (void)presentationControllerDidDismiss:(UIPresentationController *)presentationController {
    NSLog(@"The dismissal animation finished after the user swiped down.");

    // This is probably where you want to put your code that you want to call.
}

#pragma mark - UIImagePickerControllerDelegate, UINavigationControllerDelegate

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {
    NSLog(@"The user tapped the image picker's Cancel button.");
    [self dismissViewControllerAnimated:YES completion:^{
        NSLog(@"The dismissal animation finished after the user tapped Cancel.");
    }];
}

- (void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary<UIImagePickerControllerInfoKey, id> *)info {
    NSLog(@"The user selected an image from the image picker.");
    [self dismissViewControllerAnimated:YES completion:^{
        NSLog(@"The dismissal animation finished after the user selected an image.");
    }];
}

@end

这里有一个 Swift 版本：

@interface ViewController() <UIAdaptivePresentationControllerDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate>

@end

@implementation ViewController

- (IBAction)showImagePicker {
    UIImagePickerController *imagePicker = [UIImagePickerController new];
    imagePicker.delegate = self;
    imagePicker.presentationController.delegate = self;
    [self presentViewController:imagePicker animated:YES completion:nil];
}

#pragma mark - UIAdaptivePresentationControllerDelegate

- (void)presentationControllerWillDismiss:(UIPresentationController *)presentationController {
    NSLog(@"The user began to swipe down to dismiss.");
}

- (void)presentationControllerDidDismiss:(UIPresentationController *)presentationController {
    NSLog(@"The dismissal animation finished after the user swiped down.");

    // This is probably where you want to put your code that you want to call.
}

#pragma mark - UIImagePickerControllerDelegate, UINavigationControllerDelegate

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {
    NSLog(@"The user tapped the image picker's Cancel button.");
    [self dismissViewControllerAnimated:YES completion:^{
        NSLog(@"The dismissal animation finished after the user tapped Cancel.");
    }];
}

- (void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary<UIImagePickerControllerInfoKey, id> *)info {
    NSLog(@"The user selected an image from the image picker.");
    [self dismissViewControllerAnimated:YES completion:^{
        NSLog(@"The dismissal animation finished after the user selected an image.");
    }];
}

@end