How can I tell a UIGestureRecognizer to cancel an existing touch?

user_451539 0
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I have a UIPanGestureRecognizer I am using to track an object (UIImageView) below a user's finger. I only care about motion on the X axis, and if the touch strays above or below the object's frame on the Y axis I want to end the touch.

I've got everything I need for determining if a touch is within the object's Y bounds, but I don't know how to cancel the touch event. Flipping the recognizer's cancelsTouchesInView property doesn't seem to do what I want.

Thanks!

uigesturerecognizer cocoa-touch
7 Answers

According to the documentation you can subclass you gesture recogniser:

In YourPanGestureRecognizer.m:

#import "YourPanGestureRecognizer.h"

@implementation YourPanGestureRecognizer

- (void) cancelGesture {
    self.state=UIGestureRecognizerStateCancelled;
}

@end

In YourPanGestureRecognizer.h:

#import <UIKit/UIKit.h>
#import <UIKit/UIGestureRecognizerSubclass.h>

@interface NPPanGestureRecognizer: UIPanGestureRecognizer

- (void) cancelGesture;

@end

Now you can call if from anywhere

YourPanGestureRecognizer *panRecognizer = [[YourPanGestureRecognizer alloc] initWithTarget:self action:@selector(panMoved:)];
[self.view addGestureRecognizer:panRecognizer];
[...]
-(void) panMoved:(YourPanGestureRecognizer*)sender {
    [sender cancelGesture]; // This will be called twice
}

Ref: https://developer.apple.com/documentation/uikit/uigesturerecognizer?language=objc

user_23692090

Just set recognizer.state in your handlePan(_ recognizer: UIPanGestureRecognizer) method to .ended or .cancelled

user_52480990
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