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：

• 看法
  • 子视图

这些视图中的每一个都已UIPanGestureRecognizer分配。外部平移手势识别器仅对垂直平移感兴趣，因此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，子视图的平移手势在识别中始终优先。有没有办法让外部平移手势识别器首先识别，然后如果失败，子视图中的平移手势可以接管？

我尝试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 iOS 7 开始，UIGestureRecognizerDelegate 协议已经根据您的需要声明了两个委托方法，您可以使用 | 手势识别器：shouldRequireFailureOfGestureRecognizer： | 或 | gestureRecognizerShouldBegin：shouldBeRequiredToFailByGestureRecognizer： | 但以相反的方式。

以下代码片段是我的 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;
}