Forwarding UIGesture to views behind

Question

I am working on an iphone (iOS 4.0 or later) app and having some troubles with touch handling between multiple views. I am having a view structure like this

Answer 1

I did something similar some time ago. I wanted to do two different things with one finger and two or more fingers. My solution might need some tweak for you and i can't ensure everything will work exactly the same in your code-environment. I did not find proper documentation of hitTest and why it is called multiple times in a row. So i did some testing and came to a solution, how to separate one and multi-finger gestures, which worked very well for my needs.

I had this view hierarchy:

---> A superView 
 |
 ---> ScrollView - A - all touches
 |
 ---> ScrollView - B - only two+ finger scroll (exactly on top of A, completely blocking A).

I implemented the switch in hitTest of the superView:

BOOL endDrag; // indicates scrollviewB did finish
BOOL shouldClearHitTest; // bool to help calling the method clearHitTest only once.
BOOL multiTouch; // needed for the method clearHitTest to know if a multi-touch is detected or not
NSMutableArray *events; // store all events within one eventloop/touch;


- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    if (!endDrag) {
        if (!shouldClearHitTest) { // as hitTest will be called multible times in one event-loop and i need all events, i will clean the temporaries when everything is done
            shouldClearHitTest = YES;
            [[NSRunLoop mainRunLoop] performSelector:@selector(clearHitTest) target:self argument:nil order:1 modes:[NSArray arrayWithObject:NSRunLoopCommonModes]];
        }
        [events addObject:event]; // store the events so i can access them after all hittests for one touch are evaluated

        if (event.type == UIEventTypeTouches && ([_events count] > 3 || [[event allTouches] count] > 0 || _currentEvent)) { // two or more fingers detected. at least for my view hierarchy
            multiTouch = YES;
            return scrollViewB;
        }
    }else {
        endDrag = NO;
    }
    return scrollViewA;
}

- (void)clearHitTest {
    if (shouldClearHitTest) {
        shouldClearHitTest = NO;
        [events removeAllObjects];
        if (multiTouch) {
           // Do some special stuff for multiTouch
        }
        multiTouch = NO;
    }
}