Remove right navigation item, while previewing the document

问题

I am doing following code in didSelectRowAtIndexPath, document is opening but right navigation item is not removed.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (url) {
        self.pdf_viewer = [UIDocumentInteractionController interactionControllerWithURL:url];
        [self.pdf_viewer setDelegate:self];
        [self.pdf_viewer presentPreviewAnimated:YES];
     }
}

and

- (UIViewController *)documentInteractionControllerViewControllerForPreview: (UIDocumentInteractionController *) controller {
    self.navigationItem.rightBarButtonItem = nil;
    return self;
}

回答1:

On document is opening , do rightBarButtonItem = nil

if (url) {
    self.pdf_viewer = [UIDocumentInteractionController interactionControllerWithURL:url];
    [self.pdf_viewer setDelegate:self];
    [self.pdf_viewer presentPreviewAnimated:YES];
   self.navigationItem.rightBarButtonItem = nil;
}

and after closing document set again button..

来源：https://stackoverflow.com/questions/25079923/remove-right-navigation-item-while-previewing-the-document