如何取消一系列UITouch事件？ [英] How to cancel a sequence of UITouch events?

问题描述

我有一个 UIImage 视图，可以响应触摸事件。我想取消触摸序列，即，如果触摸超出某些范围，则进一步调用 touchesMoved：。我怎么能这样做？

I have a UIImage view that responds to touch events. I want to cancel the touch sequence, i.e., further calls to touchesMoved:, if the touch goes outside of certain bounds. How can I do that?

我知道在 touchesMoved：我可以检查触摸物体的坐标和忽略它，但我不知道的是如何完全取消序列。我没有看到中记录的任何方法Apple开发人员 UIResponder 参考我可以致电取消触摸序列。

I know that in touchesMoved: I can inspect the coordinates of the touch object and ignore it, but what I don't know is how to cancel the sequence altogether. I don't see any method documented in the Apple Developer UIResponder Reference that I can call to cancel a touch sequence.

推荐答案

这个解决方案可能有点麻烦，但你可以实现并手动调用

This solution may be a bit kludgy, but you could implement and manually call

- (void) touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;

我基于这个解决方案松散地对我在Apple的 iPhone示例代码网站，我修改了 touchesMoved 方法如下所示：

I am basing this solution loosely on some tweaking I did to the MoveMe sample app on Apple's iPhone sample code site where I modified the touchesMoved method to look like this:

- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
     UITouch *touch = [touches anyObject];
     if ([touch view] == placardView)
         CGPoint location = [touch locationInView:self];
         placardView.center = location;
         // I added the following line:
         [self touchesCancelled:touches withEvent:event];
         return;
}

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