OLPreViewController 在ios10上的不显示的解决办法

  if ([QLPreviewController canPreviewItem:fileURL]){

        previewController = [[QLPreviewController alloc] init];

        previewController.dataSource = self;

        previewController.delegate = self;

        if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"10.0")) {

            [self addChildViewController:previewController];

        }

        CGRect rect = preView.bounds;

        previewController.view.frame = rect;

        previewController.currentPreviewItemIndex = 0;

        [preView insertSubview:previewController.view atIndex:0];

        [previewController didMoveToParentViewController:self];

        

    }