如下面的方法的一部分,我可以问类型的recorgnier对象UISwipeGestureRecognizer *previousLocationInView,澄清需要
- (void) handleSwipeFrom:(UISwipeGestureRecognizer*)recognizer
关于其当前位置
CGPoint currentLocation = [recognizer locationInView:self];
据documentation,我应该也能得到
CGPoint previousLocation = [recognizer previousLocationInView:self];
然而,这种方法不是可用。请问我错过了什么?