Ios 向上/向下滑动手势在UIWebView中不起作用

我在UIViewController中托管了一个UIWebView， 我通过以下方式添加右/左手势：

var swipeRight = UISwipeGestureRecognizer(target: self, action: "swiped:")
swipeRight.direction = UISwipeGestureRecognizerDirection.Right
self.webView.addGestureRecognizer(swipeRight)

问题是，它无法使用向上/向下方向：

var swipeDown = UISwipeGestureRecognizer(target: self, action: "swiped:")
swipeDown.direction = UISwipeGestureRecognizerDirection.Down
self.webView.addGestureRecognizer(swipeDown)

我想这是因为滚动，我也尝试将其添加到scrollview中，但它仍然无法识别向上/向下的手势：

self.webView.scrollView.addGestureRecognizer(swipeDown)

更新：
我尝试了Harry answer，但它覆盖了向上/向下滑动的默认操作，无法滚动页面：

self.view.addGestureRecognizer(swipeUp)
self.view.addGestureRecognizer(swipeDown)

self.webView.scrollView.panGestureRecognizer.requireGestureRecognizerToFail(swipeUp)
self.webView.scrollView.panGestureRecognizer.requireGestureRecognizerToFail(swipeDown)

---

将手势识别器添加到

self.view

not

UIWebView

实例

self.view.addGestureRecognizer(swipeUp)
self.view.addGestureRecognizer(swipeDown)

在向web视图添加上/下手势识别器之后添加这两行

self.webView.scrollView.panGestureRecognizer.requireGestureRecognizerToFail(swipeUp)
self.webView.scrollView.panGestureRecognizer.requireGestureRecognizerToFail(swipeDown)

---

如果有人仍在工作，这就解决了我的问题：

webView.scrollView.panGestureRecognizer.cancelsTouchesInView = NO;

upGesture.direction = UISwipeGestureRecognizerDirectionUp;
upGesture.cancelsTouchesInView = NO;
upGesture.delegate = self;
[webView.scrollView addGestureRecognizer:upGesture];

downGesture.direction = UISwipeGestureRecognizerDirectionDown;
downGesture.cancelsTouchesInView = NO;
downGesture.delegate = self;
[webView.scrollView addGestureRecognizer:downGesture];



- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
    return [gestureRecognizer isKindOfClass:[UISwipeGestureRecognizer class]] && [otherGestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]];
}

---

@Harry这个答案在ObjectiveC中，我怎样才能在swift中实现？谢谢，现在它工作了，但是它覆盖了默认的向上/向下滑动操作，我无法滚动页面抱歉，但我仍然无法滚动，我得到了我定义的手势，但无法向上/向下滚动UIWEBVIEW，我做错了什么？我编辑了我的问题