contentScaleFactor has no effect on UIWebView

I am trying zoom my views with use of contentScaleFactor. From the root UIView, I set the the contentScaleFactor of subviews iteratively to 2.0 when double tap is detected. But after the zoom I found there is a subview of UIWebView and it's very blurry when its contentScaleFactor is set 开发者_如何转开发to 2 while all other UIViews are very clear. I also found that double tap on the UIWebView doesn't pass the gesture to its superview like other UIViews.

1. Is there any way for UIWebView to achieve the same effect of setting contentScaleFactor on other UIViews?
2. How to transfer the double tap gesture to UIWebView's superview?

Thanks very much!!!