How to ignore touch events and pass them to another subview's UIControl objects?

Question

I have a custom UIViewController whose UIView takes up a corner of the screen, but most of it is transparent except for the parts of it that have some buttons and stuff on it. Due to the layout of the objects on that view, the view's frame can cover up some buttons beneath it. I want to be able to ignore any touches on that view if they aren't touching anything important on it, but I seem to only be able to pass along actual touch events (touchesEnded/nextResponder stuff). If I have a UIButton or something like that which doesnt use touchesEnded, how do I pass the touch event along to that?

I can't just manually figure out button selector to call, because this custom ViewController can be used on many different views. I basically need a way to call this:

[self.nextResponder touchesEnded:touches withEvent:event];

on UIControl types as well.

Answer 1

Probably the best way to do this is to override hitTest:withEvent: in the view that you want to be ignoring touches. Depending on the complexity of your view hierarchy, there are a couple of easy ways to do this.

If you have a reference to the view underneath the view to ignore:

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

    // If the hitView is THIS view, return the view that you want to receive the touch instead:
    if (hitView == self) {
        return otherView;
    }
    // Else return the hitView (as it could be one of this view's buttons):
    return hitView;
}

If you don't have a reference to the view:

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

    // If the hitView is THIS view, return nil and allow hitTest:withEvent: to
    // continue traversing the hierarchy to find the underlying view.
    if (hitView == self) {
        return nil;
    }
    // Else return the hitView (as it could be one of this view's buttons):
    return hitView;
}

I would recommend the first approach as being the most robust (if it's possible to obtain a reference to the underlying view).

Answer 2

Swift answer:

You can create a UIView subclass, IgnoreTouchView. In a storyboard, set it on the VC's view(s) you want to pass through touches:

class IgnoreTouchView : UIView {
    override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        let hitView = super.hitTest(point, with: event)
        if hitView == self {
            return nil
        }
        return hitView
    }
}

Note that you must set UserInteractionEnabled to true, for the UIView in question!

Answer 3

You could also disable user interaction so that touch events are ignored and are passed to the parent.

In Swift:

yourView.isUserInteractionEnabled = false

Answer 4

I haven't found a good way to pass UITouch events between objects. What usually works better is to implement hitTest and return nil if the point isn't in the view that you want to handle it:

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

Answer 5

This is an old question, and it comes up at the top of searches. So, I thought I'd post another possible solution that might work better for your situation. In my case I wanted to drag a label on top of another label and I wanted to get the label below in the hitTest. The simplest thing to do is to set the userInteractionEnabled to NO or false, then do your hitTest, and then set it back again if you need to move it again. Here's a code sample in Swift:

override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
    let touch = touches.first
    let location = touch?.locationInView(self.view)
    self.label1.userInteractionEnabled = false
    let view = self.view.hitTest(location!, withEvent: nil) as? UILabel
    print(view?.text)
    self.label1.userInteractionEnabled = true
}

Answer 6

My problem was similar: I had a UIControl with complex touch responders, but it acted funny when embedded in a scroll view...

This prevents parent scrolling (or can be modified to prevent other interactions) when sub view has an active touch gesture.

My solution:

Create a delegate protocol for didBeginInteraction and didEndInteraction in sub view.

Call delegate.didBeginInteraction from touchesBegan

Call delegate.didEndInteraction from touchesEnded and touchesCancelled

In parent controller, implement didBegin and didEnd protocol, set delegate

Then set scrollView.scrollEnabled = NO in didBegin, scrollEnabled = YES in didEnd.

Hope this helps someone with a slightly different use case than the question posed!