iOS: Warning: Attempt to present

在iOS8中，弹出ActionSheet后选择其中一项，然后在ActionSheet的代理方法actionSheet(actionSheet:clickedButtonAtIndex:)中使用了performSegueWithIdentifier方法来跳转到下一个ViewController时，发现ViewController不但没有跳转，控制台却出现了以下警告：

-------UIGraphicsBeginImageContext
2021-08-16 13:42:30.977397+0800 ImageCroppingDemo[615:63044] [Presentation] Attempt to present <CXImageCropper: 0x10104acf0> on <ViewController: 0x10070b3d0> (from <ViewController: 0x10070b3d0>) which is already presenting <UIImagePickerController: 0x10181fe00>.

以下是解决办法：

1.跳转ViewController这种类型的代码最好写到actionSheet(actionSheet:, didDismissWithButtonIndex)方法中，保证ActionSheet消失后才跳转。

2.如果确实需要在actionSheet(actionSheet: clickedButtonAtIndex: )就跳转，那么可以做个延时，比如0.1秒之后再调用performSegueWithIdentifier方法。

[self dismissViewControllerAnimated:YES
                             completion:^{
                                ModalViewController *sampleView = [[ModalViewController alloc] init];
                                [self presentModalViewController:sampleView animated:YES];
                             }];

或

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    
    [picker dismissViewControllerAnimated:YES completion:^{
        //此方法之后再调用presentViewController   [self presentViewController:vc animated:YES completion:nil];
        [self operationImagePhotoInfo:info];
    }];
}