Right thumbnail bar of QLPreviewController disappeared in iOS 11

Hi,

I'm opening a pdf using QLPreviewController, which usually appears with a right thumbnail bar in iOS 10. But when I run the app on iOS 11, the thumbnail bar disappeared. I'm using the following Objective-C code to preview a pdf.

-(void)viewDidLoad
{
    if ([QLPreviewController canPreviewItem:[[NSBundle mainBundle] URLForResource:@"alice" withExtension:@"pdf"]])
    {
        QLPreviewController *previewController = [[QLPreviewController alloc] init];
        previewController.dataSource = self;
        [previewController.view.frame =
          CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width/1.2, self.view.frame.size.height)];

        [self addChildViewController:previewController];
        [viewQuickLook addSubview:previewController.view];
        [previewController didMoveToParentViewController:self];
    }
}


-(NSInteger) numberOfPreviewItemsInPreviewController:(QLPreviewController *)controller
{
    return 1;
}

- (id <QLPreviewItem>)previewController:(QLPreviewController *)controller previewItemAtIndex:(NSInteger)index
{
    NSURL *pdfURL = [[NSBundle mainBundle] URLForResource:@"alice" withExtension:@"pdf"];
    return pdfURL;
}

Is it natural in iOS 11?

Also I set my pdf preview screen width to 80%. But the pdf is not fitting to the screen and the content became horizontally scrollable. Is there anybody who encountered or fixed that?