iOS5 UITapRecognizer for UIScrollView interfering

问题:

I have a bunch of UIButtons within a UIView within a UIScrollView. I'm trying to add a tap recognizer to the scroll view. The tap recognizer fires, but now none of my buttons work.

I know that in iOS5, UIScrollView can somehow pass a touch event down to the control hierarchy after being done with it. Anyone can help me figure out how to do this?

回答1:

Set the UIGestureRecognizer property cancelsTouchesInView to NO.

UITapGestureRecognizer *singleTapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self 
                                                                                             action:@selector(singleTap:)];
singleTapGestureRecognizer.numberOfTapsRequired = 1;
singleTapGestureRecognizer.enabled = YES;
singleTapGestureRecognizer.cancelsTouchesInView = NO;
[tapableView addGestureRecognizer:singleTapGestureRecognizer];
[singleTapGestureRecognizer release];

From UIGestureRecognizer Class Reference

A Boolean value affecting whether touches are delivered to a view when a gesture is recognized.

When this property is YES (the default) and the receiver recognizes its gesture, the touches of that gesture that are pending are not delivered to the view and previously delivered touches are cancelled through a touchesCancelled:withEvent: message sent to the view. If a gesture recognizer doesn’t recognize its gesture or if the value of this property is NO, the view receives all touches in the multi-touch sequence.

回答2:

For me a combo of the above answers worked

UITapGestureRecognizer *tapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(userDidTap:)];
tapRecognizer.cancelsTouchesInView = YES;
tapRecognizer.delegate = self;
[tapRecognizer requireGestureRecognizersToFail:self.scrollView.gestureRecognizers];
[self.view addGestureRecognizer:tapRecognizer];

-

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    if ([touch.view.superview isKindOfClass:[UIButton class]] || [touch.view isKindOfClass:[UIButton class]])
    {
        return NO;
    }
    return YES;
}

回答3:

You could also use the gestureRecognizer:shouldReceiveTouch: method of the UIGestureRecognizerDelegate, which is documented here, to accomplish the same thing. It offers a little more flexibility, for instance, if you want to cancel certain touches, but not others. Here's an example,

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    if ([touch.view.superview isKindOfClass:[UIButton class]]) return NO;

    return YES;
}