Why does UINavigationBar steal touch events?

Question

I have a custom UIButton with UILabel added as subview. Button perform given selector only when I touch it about 15points lower of top bound. And when I tap above that area

Answer 1

I found out the answer here(Apple Developer Forum).

Keith at Apple Developer Technical Support, on 18th May 2010 (iPhone OS 3):

I recommend that you avoid having touch-sensitive UI in such close proximity to the nav bar or toolbar. These areas are typically known as "slop factors" making it easier for users to perform touch events on buttons without the difficulty of performing precision touches. This is also the case for UIButtons for example.

But if you want to capture the touch event before the navigation bar or toolbar receives it, you can subclass UIWindow and override: -(void)sendEvent:(UIEvent *)event;

Also I found out,that when I touch the area under the UINavigationBar, the location.y defined as 64,though it was not. So I made this:

CustomWindow.h

@interface CustomWindow: UIWindow 
@end

CustomWindow.m

@implementation CustomWindow
- (void) sendEvent:(UIEvent *)event
{       
  BOOL flag = YES;
  switch ([event type])
  {
   case UIEventTypeTouches:
        //[self catchUIEventTypeTouches: event]; perform if you need to do something with event         
        for (UITouch *touch in [event allTouches]) {
          if ([touch phase] == UITouchPhaseBegan) {
            for (int i=0; i<[self.subviews count]; i++) {
                //GET THE FINGER LOCATION ON THE SCREEN
                CGPoint location = [touch locationInView:[self.subviews objectAtIndex:i]];

                //REPORT THE TOUCH
                NSLog(@"[%@] touchesBegan (%i,%i)",  [[self.subviews objectAtIndex:i] class],(NSInteger) location.x, (NSInteger) location.y);
                if (((NSInteger)location.y) == 64) {
                    flag = NO;
                }
             }
           }  
        }

        break;      

   default:
        break;
  }
  if(!flag) return; //to do nothing

    /*IMPORTANT*/[super sendEvent:(UIEvent *)event];/*IMPORTANT*/
}

@end

In AppDelegate class I use CustomWindow instead of UIWindow.

Now when I touch area under navigation bar, nothing happens.

My buttons still don't get touch events,because I don't know how to send this event (and change coordinates) to my view with buttons.

Answer 2

I noticed that if you set userInteractionEnabled to OFF, the NavigationBar doesn't "steal" the touches anymore.

So you have to subclass your UINavigationBar and in your CustomNavigationBar do this:

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

    if ([self pointInside:point withEvent:event]) {
        self.userInteractionEnabled = YES;
    } else {
        self.userInteractionEnabled = NO;
    }

    return [super hitTest:point withEvent:event];
}

Info about how to subclass UINavigationBar you can find here.

Answer 3

This solved my problem..

I added hitTest:withEvent: code to my navbar subclass..

 -(UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
        int errorMargin = 5;// space left to decrease the click event area
        CGRect smallerFrame = CGRectMake(0 , 0 - errorMargin, self.frame.size.width, self.frame.size.height);
        BOOL isTouchAllowed =  (CGRectContainsPoint(smallerFrame, point) == 1);

        if (isTouchAllowed) {
            self.userInteractionEnabled = YES;
        } else {
            self.userInteractionEnabled = NO;
        }
        return [super hitTest:point withEvent:event];
    }

Answer 4

Give a extension version according to Bart Whiteley. No need to subclass.

@implementation UINavigationBar(Xxxxxx)

- (UIView*)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
    UIView *v = [super hitTest:point withEvent:event];
    return v == self ? nil: v;
}

@end

Answer 5

I just wanted to share another prospective to solving this problem. This is not a problem by design, but it was meant to help user get back or navigate. But we need to put things tightly in or below nav bar and things look sad.

First lets look at the code.

class MyNavigationBar: UINavigationBar {
private var secondTap = false
private var firstTapPoint = CGPointZero

override func pointInside(point: CGPoint, withEvent event: UIEvent?) -> Bool {
    if !self.secondTap{
        self.firstTapPoint = point
    }

    defer{
        self.secondTap = !self.secondTap
    }

    return  super.pointInside(firstTapPoint, withEvent: event)
}

}

You might be see why am i doing second touch handling. There is the recipe to the solution.

Hit test is called twice for a call. The first time the actual point on the window is reported. Everything goes well. On the second pass, this happens.

If system sees a nav bar and the hit point is around 9 pixels more on Y side, it tries to decrease that gradually to below 44 points which is where the nav bar is.

Take a look at the screen to be clear.

So theres a mechanism that will use nearby logic to the second pass of hittest. If we can know its second pass and then call the super with first hit test point. Job done.

The above code does that exactly.

Answer 6

There are 2 things that might be causing problems.

1. Did you try setUserInteractionEnabled:NO for the label.

2. Second thing i think might work is apart from that after adding label on top of button you can send the label to back (it might work, not sure although)

   [button sendSubviewToBack:label];

Please let me know if the code works :)