UITapGestureRecognizer - make it work on touch down, not touch up?

Question

What I'm using the tap event for is very time-sensitive, so I'm curious if it's possible to make UITapGestureRecognizer activate when the user simply touches down, rather than requiring them to touch up as well?

Answer 1

Use a UILongPressGestureRecognizer and set its minimumPressDuration to 0. It will act like a touch down during the UIGestureRecognizerStateBegan state.

For Swift 4+

func setupTap() {     let touchDown = UILongPressGestureRecognizer(target:self, action: #selector(didTouchDown))     touchDown.minimumPressDuration = 0     view.addGestureRecognizer(touchDown) }  @objc func didTouchDown(gesture: UILongPressGestureRecognizer) {     if gesture.state == .began {         doSomething()     } } 

For Objective-C

-(void)setupLongPress {    self.longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(didLongPress:)];    self.longPress.minimumPressDuration = 0;    [self.view addGestureRecognizer:self.longPress]; }  -(void)didLongPress:(UILongPressGestureRecognizer *)gesture {    if (gesture.state == UIGestureRecognizerStateBegan){       [self doSomething];    } } 

Answer 2

Create your custom TouchDownGestureRecognizer subclass and implement gesture in touchesBegan:

TouchDownGestureRecognizer.h

#import <UIKit/UIKit.h>  @interface TouchDownGestureRecognizer : UIGestureRecognizer  @end 

TouchDownGestureRecognizer.m

#import "TouchDownGestureRecognizer.h" #import <UIKit/UIGestureRecognizerSubclass.h>  @implementation TouchDownGestureRecognizer -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{     if (self.state == UIGestureRecognizerStatePossible) {         self.state = UIGestureRecognizerStateRecognized;     } }  -(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{     self.state = UIGestureRecognizerStateFailed; }  -(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{     self.state = UIGestureRecognizerStateFailed; }   @end 

implementation:

#import "TouchDownGestureRecognizer.h"     TouchDownGestureRecognizer *touchDown = [[TouchDownGestureRecognizer alloc] initWithTarget:self action:@selector(handleTouchDown:)];     [yourView addGestureRecognizer:touchDown];  -(void)handleTouchDown:(TouchDownGestureRecognizer *)touchDown{     NSLog(@"Down"); } 

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Swift implementation:

import UIKit import UIKit.UIGestureRecognizerSubclass  class TouchDownGestureRecognizer: UIGestureRecognizer {     override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent)     {         if self.state == .Possible         {             self.state = .Recognized         }     }      override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent)     {         self.state = .Failed     }      override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent)     {         self.state = .Failed     } } 

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Here is the Swift syntax for 2017 to paste:

import UIKit.UIGestureRecognizerSubclass  class SingleTouchDownGestureRecognizer: UIGestureRecognizer {     override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {         if self.state == .possible {             self.state = .recognized         }     }     override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {         self.state = .failed     }     override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent) {         self.state = .failed     } } 

Note that this is a drop-in replacement for UITap. So in code like...

func add(tap v:UIView, _ action:Selector) {     let t = UITapGestureRecognizer(target: self, action: action)     v.addGestureRecognizer(t) } 

you can safely swap to....

func add(hairtriggerTap v:UIView, _ action:Selector) {     let t = SingleTouchDownGestureRecognizer(target: self, action: action)     v.addGestureRecognizer(t) } 

Testing shows it will not be called more than once. It works as a drop-in replacement; you can just swap between the two calls.