在webview中添加手势，必须实现以下代理才有效；
func gestureRecognizer(gestureRecognizer:UIGestureRecognizer, shouldRecognizeSimultaneouslyWithGestureRecognizer otherGestureRecognizer:UIGestureRecognizer) ->Bool{return true}
若webview中有js的点击事件，如何区分？
经debug发现，js点击事件的gesture属于WKSyntheticClickTapGestureRecognizer，这是个运行时的属性，直接取是取不到的。但是我们可以用description属性，即otherGestureRecognizer.description，返回的是一个描述字符串，实现如下：
func gestureRecognizer(gestureRecognizer:UIGestureRecognizer, shouldRecognizeSimultaneouslyWithGestureRecognizer otherGestureRecognizer:UIGestureRecognizer) ->Bool{
if otherGestureRecognizer.description.containsString("WKSyntheticClickTapGestureRecognizer") {
return false
} return true }
