Question

I have two views each of which contain two subviews.

Hit detection is working fine as long as the two top views do not overlap.
Hence I can touch subview marked A in the left side of the image below.

However as soon as the top two views overlap, there is just no way that the A view receives touches as view 1 is “above” view 2 and “eats” the touch.

Both View 1 and View 2 detect touches, as they can be moved around, hence need to detect and react to touches “in between” subviews.

This means that my two “top views” detection should say: “Oh, wait a minute, maybe I am ovelapping some other view and should pass the event to it, and only start a drag/move around if and only if no other view is ‘below me'”.

How would I do that?

Edit:
Thanks jaydee3

This didn’t work at first, resulting into an infinite recursion: each view deferring to its sibling, which in turn defers back to the initiating view:

- (UIView *) hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    UIView * hit =  [super hitTest:point withEvent:event] ;

    if (hit == self) {
        for (UIView * sibling in self.superview.subviews) {
            if (sibling != self) {
                CGPoint translated = [self convertPoint:point toView:sibling] ;
                UIView * other = [sibling hitTest:translated withEvent:event] ;
                if (other) {
                    return other ;
                }
            }
        }
    }

    return hit ;
}

So, I added a “marked set” to keep track of which view already had been visited, and it now all works 🙂

- (UIView *) hitTest: (CGPoint) point withEvent: (UIEvent *) event {

    static NSMutableSet * markedViews = [NSMutableSet setWithCapacity:4] ;

    UIView * hit =  [super hitTest:point withEvent:event] ;

    if (hit == nil) return nil ;

    if (hit == self) {
        for (UIView * sibling in hit.superview.subviews) {
            if (sibling != hit) {
                if ([markedViews containsObject:sibling]) {
                    continue ;
                }

                [markedViews addObject:sibling] ;
                CGPoint translated = [hit convertPoint:point toView:sibling] ;
                UIView * other = [sibling hitTest:translated withEvent:event] ;
                [markedViews removeObject:sibling] ;

                if (other) {
                    return other ;
                }
            }
        }
    }

    return hit ;
}

Answer 1

Make a custom subclass for your view (that containts the other two subviews) and overwrite the hitTest: method for it. In that method, check if the hitTest view is one of the two subviews, else return nil. So all touches will be ignored on your surrounding view. Resulting in a touch on the view below, which can handle it itself.

//edit: (You get the hitTest view by calling UIView* view = [super hitTest:withEvent:];.)

//edit2: i thought more of smth like that: 🙂

- (UIView *) hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    UIView * hit =  [super hitTest:point withEvent:event] ;

    if (hit == self) {
        return nil;
    }

    return hit ;
}

😉