在webview中添加手勢，必須實現以下代理才有效；
func gestureRecognizer(gestureRecognizer:UIGestureRecognizer, shouldRecognizeSimultaneouslyWithGestureRecognizer otherGestureRecognizer:UIGestureRecognizer) ->Bool{return true}
若webview中有js的點擊事件，如何區分？
經debug發現，js點擊事件的gesture屬于WKSyntheticClickTapGestureRecognizer，這是個運行時的屬性，直接取是取不到的。但是我們可以用description屬性，即otherGestureRecognizer.description，返回的是一個描述字符串，實現如下：
func gestureRecognizer(gestureRecognizer:UIGestureRecognizer, shouldRecognizeSimultaneouslyWithGestureRecognizer otherGestureRecognizer:UIGestureRecognizer) ->Bool{
if otherGestureRecognizer.description.containsString("WKSyntheticClickTapGestureRecognizer") {
return false
}?return true?}
