解决两个平移手势识别器之间的冲突

Question

我有以下层次结构：

• 查看
  • 子视图

每个视图都分配了UIPanGestureRecognizer。外部平移手势识别器仅对垂直平移感兴趣，因此我实现了委托方法：

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)panGestureRecognizer {
    CGPoint velocity = [panGestureRecognizer velocityInView:panGestureRecognizer.view];
    return fabs(velocity.y) > fabs(velocity.x);
}

然而，Subview的平移手势始终优先于识别。有没有办法让外部手势识别器首先识别，然后如果失败，从子视图中平移手势可以接管吗？

我尝试了同时识别并且它有效，但是两个识别器都开始淘汰：

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer 

    shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
        return YES;
    }

Answer 1

自iOS 7起，UIGestureRecognizerDelegate协议已经为您的需要声明了两种委托方法，您可以使用 | gestureRecognizer：shouldRequireFailureOfGestureRecognizer： | 要么 | gestureRecognizerShouldBegin：shouldBeRequiredToFailByGestureRecognizer： |但反过来说。

以下代码段是我的UIPanGestureRecognizer委托实现：

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)panGestureRecognizer {
    CGPoint velocity = [panGestureRecognizer velocityInView:panGestureRecognizer.view];
    return fabs(velocity.y) > fabs(velocity.x);
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
    if (otherGestureRecognizer == panGestureOfSubView) {
        return YES;
    }

    return NO;
}

Answer 2

此代码可能会有所帮助。这是我写的允许拖动特定视图的内容，但不是它的子视图：

func gestureRecognizer(gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWithGestureRecognizer otherGestureRecognizer: UIGestureRecognizer) -> Bool {

        if gestureRecognizer == longTouchGesture && otherGestureRecognizer == panTouchGesture && gestureRecognizer.view?.hitTest(gestureRecognizer.locationInView(gestureRecognizer.view), withEvent: nil) == self {
            print("returning true")
            return true
        }
        print("returning false")
        return false
    }