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

Question

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

Answer 1

This little trick works for me.

@implementation UIGestureRecognizer (Cancel)

- (void)cancel {
    self.enabled = NO;
    self.enabled = YES;
}

@end

From the UIGestureRecognizer @enabled documentation:

Disables a gesture recognizers so it does not receive touches. The default value is YES. If you change this property to NO while a gesture recognizer is currently recognizing a gesture, the gesture recognizer transitions to a cancelled state.

Answer 2

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

Answer 3

Obj-C:

recognizer.enabled = NO;
recognizer.enabled = YES;

Swift 3:

recognizer.isEnabled = false
recognizer.isEnabled = true

Answer 4

@matej's answer in Swift.

extension UIGestureRecognizer {
  func cancel() {
    isEnabled = false
    isEnabled = true
  }
}

Answer 5

How about this from the apple docs:

@property(nonatomic, getter=isEnabled) BOOL enabled

Disables a gesture recognizers so it does not receive touches. The default value is YES. If you change this property to NO while a gesture recognizer is currently recognizing a gesture, the gesture recognizer transitions to a cancelled state.

Answer 6

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