how to forbid pdfview to zoom out when the pdfview's size is equal to the screen size

guys.new to iphone . i've download demo "ZoomingPdfViewer",it's cool.but i don't want the behaviour tha开发者_运维技巧t the pdfview will zoom out smaller than the screen size. i searched int the api doc, and found that when the viewForZoomingInScrollView method return nil,no zoom will happen. i try to do this;

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView

{      
    return pdfView;

}

but i just can't judge weather the user is to zooming in or zooming out.

so,is there any other ways to forbid pdfview to zoom out when the pdfview's size is equal to the screen size.

You should compute and set the scrollview's maximumZoomScale property.