Question

I have a draggable view that a user will touch, but some rectangles of it will have no image (alpha 0).

When a user clicks the transparent region (I am able to construct the transparent region without the alpha info), I want the view (same class) below the transparent region to detect the touch.

My strategy is to let the view ignore the touch when user touches the transparent area and hope the view below it will automatically catch the touch event. But I’m not sure if this will work. (setting things up to test this will take some time)

Should I take a different approach or the above strategy would work?

Thank you.

Answer 1

Try overwriting the method hitTest:withEvent: in the superview. You can make hitTest:withEvent: return the view you want to handle a given event.

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    for (UIView *v in self.subviews){
        CGPoint pointInB = [v convertPoint:point fromView:self];
        if ([v someConditionYouMayWantToTestFor]){
            return v;
        }
    }
    return nil;
}

The method someConditionYouMayWantToTestFor is where you test if you want the subview to capture the event or not.