self.parentViewController在第一次执行时有效，但之后为

Question

我有一些代码可以在导航控制器中构建和显示viewController。第一次通过handleDoubleTapRecognizer一切都按预期工作。但是，此后每次触发handleDoubleTapRecognizer时，handleDoubleTapRecognizer内置的导航控制器及其内容控制器都不会出现，而是在控制台中收到这条令人愉快的消息......

Warning: Attempt to present <UINavigationController: 0x7bbafa00> on <iRpImageViewerViewController: 0x80164580> whose view is not in the window hierarchy!

另请注意，[self.view superview]返回nil，因此某些东西完全破坏了从该视图到其父视图的连接。

...

@implementation iRpImageViewerViewController
{
    IGGridView *theMainImageGridviewControl;
    iRpImageSet *thePropertyImageSet;
    iRpImageFilmstripViewController *theFilmstripViewController;
    iRpImageAndMedia *initialMediaItem;  // The item to display when first loaded.
    UIImageView *primaryImageMarker;
    UINavigationController *imageEditorNavController;
    iRpImageEditorViewController *imageEditorVC;

}

...

-(void)handleDoubleTapRecognizer:(UITapGestureRecognizer*)recognizer
    {
        NSLog(@"Double Tapped on ImageViewerViewController's main image, so opening editor");

        IGCellPath *pathForCurrentCell = [self pathForCurrentCell];
        iRpImageAndMedia *imageAndMediaItem = [thePropertyImageSet objectAtIndex:pathForCurrentCell.columnIndex];

        imageEditorVC = [[iRpImageEditorViewController alloc] initWithImageAndMediaItem:imageAndMediaItem];
        imageEditorVC.navigationItem.title = @"Photo Details Editor";
        imageEditorVC.edgesForExtendedLayout = UIRectEdgeNone;

        imageEditorNavController = [[UINavigationController alloc] initWithRootViewController:imageEditorVC];
        imageEditorNavController.modalPresentationStyle = UIModalPresentationFormSheet;
        imageEditorNavController.topViewController.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(imageEditorDone)];
        imageEditorNavController.topViewController.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:@selector(imageEditorCancelled)];
        imageEditorNavController.preferredContentSize = imageEditorVC.view.frame.size;

        NSLog(@"%@'s parentViewController is %@",self, self.parentViewController);

        [self presentViewController:imageEditorNavController animated:YES completion:^(void){ }];

    }


-(void)imageEditorDone
    {
        [self dismissViewControllerAnimated:YES completion:nil];
    }


-(void)imageEditorCancelled
    {
        [self dismissViewControllerAnimated:YES completion:nil];
    }