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

每个视图都已分配 UIPanGestureRecognizer。外部平移手势识别器只对垂直平移感兴趣，所以我为此实现了委托方法：

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

然而，Subview 的平移手势总是优先于识别。有什么方法可以让外部平移手势识别器先识别，如果失败，子视图中的平移手势可以接管？

我试过同时识别并且它有效，但随后两个识别器都开始平移：

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer 

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

Answer 1

从iOS7开始，UIGestureRecognizerDelegate Protocol已经声明了两个委托方法来满足你的需要，你可以使用 |gestureRecognizer:shouldRequireFailureOfGestureRecognizer:| 要么 |gestureRecognizerShouldBegin:shouldBeRequiredToFailByGestureRecognizer:|但以相反的方式。

以下片段是我的 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

这段代码可能会有帮助。这是我写的允许拖动特定视图，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
    }