How to let a UIView handle a tap gesture then have the tap gesture passed down to another UIView lying beneath?

The documentation says set:

recognizer.cancelsTouchesInVew = NO;

and add the recognizer to the top view.

I tried and it does not work.

Below is the code pattern I used:

UIView *custom_overlay_1 = [[UIView alloc] initWithFrame : given_frame];
UIView *custom_overlay_2 = [[UIView alloc] initWithFrame : given_frame];

UITapGestureRecognizer *custom_recognizer_1, *custom_recognizer_2;

custom_recognizer_1 = [[UITapGestureRecognizer alloc]
                                     initWithTarget : self
                                     action         :@selector(handle_tap_1:)];

custom_recognizer_2 = [[UITapGestureRecognizer alloc]
                                     initWithTarget : self
                                     action         :@selector(handle_tap_2:)];

     
[custom_recognizer_1 setCancelsTouchesInView: NO];
[custom_recognizer_2 setCancelsTouchesInView: NO];

[custom_overlay_1 addGestureRecognizer: custom_recognizer_1];
[custom_overlay_2 addGestureRecognizer: custom_recognizer_2];

[self.view addSubview custom_overlay_2];
[self.view addSubview custom_overlay_1];

- (int) handle_tap_1 : (UITapGestureRecognizer *) gesture
{
   
    NSLog(@" *** *** handle_tap_1 !!!");
    
    if (gesture.state == UIGestureRecognizerStateRecognized)
        NSLog(@" *** *** recognized tap detected in handle_tap_1 !!!");
    
    return (0);    
}


- (int) handle_tap_2 : (UITapGestureRecognizer *) gesture
{
   
    NSLog(@" *** *** handle_tap_2 !!!");
    
    if (gesture.state == UIGestureRecognizerStateRecognized)
        NSLog(@" *** *** recognized tap detected in handle_tap_2 !!!");
    
    return (0);    
}

The problem is custom_overlay_1 is able to catch the tap gesture but custom_overlay_2 doesn’t.

To allow custom_overlay_2 's tap gesture to be regconized, you need to provide custom delegate to custom_recognizer_1 instead and overwrite method gestureRecognizer(_:shouldRecognizeSimultaneouslyWith:) (simply return true) instead as its docs specify:

Return Value

true to allow both gestureRecognizer and otherGestureRecognizer to recognize their gestures simultaneously. The default implementation returns false—no two gestures can be recognized simultaneously.

Setting cancelsTouchesInView = false doesn't work because it just alter the way touch events be sent to UIView not to other gesture regconizers, you can read docs of UIGestureRegconizer for more detail:

A window delivers touch events to a gesture recognizer before it delivers them to the hit-tested view attached to the gesture recognizer. Generally, if a gesture recognizer analyzes the stream of touches in a multi-touch sequence and doesn’t recognize its gesture, the view receives the full complement of touches. If a gesture recognizer recognizes its gesture, the remaining touches for the view are canceled. The usual sequence of actions in gesture recognition follows a path determined by default values of the cancelsTouchesInView, delaysTouchesBegan, delaysTouchesEnded properties:

@interface ViewController : UIViewController<UIGestureRecognizerDelegate>
@end

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    UIView *custom_overlay_1 = [[UIView alloc] initWithFrame : CGRectMake(100, 200, 200, 200)];
    [custom_overlay_1 setBackgroundColor:UIColor.redColor];
    UIView *custom_overlay_2 = [[UIView alloc] initWithFrame : CGRectMake(0, 0, 100, 100)];
    [custom_overlay_2 setBackgroundColor:UIColor.greenColor];
    
    UITapGestureRecognizer *custom_recognizer_1, *custom_recognizer_2;
    
    custom_recognizer_1 = [[UITapGestureRecognizer alloc]
                           initWithTarget : self
                           action         :@selector(handle_tap_1:)];
    [custom_recognizer_1 setDelegate:self];
    
    custom_recognizer_2 = [[UITapGestureRecognizer alloc]
                           initWithTarget : self
                           action         :@selector(handle_tap_2:)];
    
    
    [custom_recognizer_1 setCancelsTouchesInView: NO];
    [custom_recognizer_2 setCancelsTouchesInView: NO];
    
    [custom_overlay_1 addGestureRecognizer: custom_recognizer_1];
    [custom_overlay_2 addGestureRecognizer: custom_recognizer_2];
    
    [self.view addSubview:custom_overlay_1];
    [custom_overlay_1 addSubview:custom_overlay_2];
}

- (int) handle_tap_1 : (UITapGestureRecognizer *) gesture
{
    
    NSLog(@" *** *** handle_tap_1 !!!");
    
    if (gesture.state == UIGestureRecognizerStateRecognized)
        NSLog(@" *** *** recognized tap detected in handle_tap_1 !!!");
    
    return (0);
}


- (int) handle_tap_2 : (UITapGestureRecognizer *) gesture
{
    
    NSLog(@" *** *** handle_tap_2 !!!");
    
    if (gesture.state == UIGestureRecognizerStateRecognized)
        NSLog(@" *** *** recognized tap detected in handle_tap_2 !!!");
    
    return (0);
}

//MARK: UIGestureRecognizerDelegate
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
    return YES;
}
@end

Also note that if you add custom_overlay_1 and custom_overlay_2 to the same superview, their gesture recognizer can not both receive touch.

                   superview
                   /       \
       custom_overlay_1   custom_overlay_2

For example, on UI custom_overlay_2 on top of custom_overlay_1 , you tap on custom_overlay_2 , it will be the hit-tested view, the responder chain will be:

custom_overlay_2 -> superview

Therefore custom_overlay_1 and its gesture regconizers can not receive touch events.

To allow both custom_overlay_1 and custom_overlay_2 receive events, you need to make one become subview to another views like in my example code when custom_overlay_2 become subview of custom_overlay_1. Now responder chain will be ( when tap on custom_overlay_2):

custom_overlay_2 -> custom_overlay_1 -> superview -> ViewControler...