averydev averydev - 9 days ago 5
Objective-C Question

Disable touches on UIView background so that buttons on lower views are clickable

Basically, here is my view hierarchy (and I appologize if this is hard to read... I'm new here so posting suggestions happily accepted)




--AppControls.xib

-------(UIView)ControlsView

----------------- (UIView)TopBar

----------------- -------------- btn1, btn2, btn3

----------------- UIView)BottomBar

----------------- --------------slider1 btn1, btn2

--PageContent.xib

----------------- (UIView)ContentView

----------------- --------------btn1, btn2, btn3

----------------- --------------(UIImageView)FullPageImage




My situation is that I want to hide and show the controls when tapping anywhere on the PageContent thats not a button and have the controls show, much like the iPhone Video Player. However, when the controls are shown I still want to be able to click the buttons on the PageContent.

I have all of this working, except for the last bit. When the controls are showing the background of the controls receives the touch events instead of the view below. And turning off user interaction on the ControlsView turns it off on all its children.

I have tried overriding HitTest on my ControlsView subclass as follows which I found in a similar post:

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event{
UIView *hitView = nil;
NSArray *subviews = [self subviews];
int subviewCount = [subviews count];
for (int subviewIndex = 0; !hitView && subviewIndex < subviewCount; subviewIndex++){
hitView = [[subviews objectAtIndex:subviewIndex] hitTest:point withEvent:event];
}
return hitView;
}


However, at this point my slider doesn't work, nor do most of the other buttons, and really, things just start getting weird.

So my question is in short: How do I let all the subviews of a view have touch events, while the super view's background is unclickable, and the buttons on views below can receive touch events.

Thanks!

Answer

You're close. Don't override -hitTest:withEvent:. By the time that is called, the event dispatcher has already decided that your subtree of the hierarchy owns the event and won't look elsewhere. Instead, override -pointInside:withEvent:, which is called earlier in the event processing pipeline. It's how the system asks "hey view, does ANYONE in your hierarchy respond to an event at this point?". If you say NO, event processing continues below you in the visible stack.

Per the documentation, the default implementation just checks whether the point is in the bounds of the view at all.

Your strategy is to say "yes" when any of your subviews is at that coordinate, but say "no" when the touch would be hitting the background.

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
    for (UIView * view in [self subviews]) {
        if (view.userInteractionEnabled && [view pointInside:[self convertPoint:point toView:view] withEvent:event]) {
            return YES;
        }
    }
    return NO;
}
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