UITapGestureRecognizer - make it work on touch down, not touch up?
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");
}
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
}
}
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.
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];
}
}
This is another solution. Create subclass of UIControl. You can use it like UIView even in Storyboard because UIControl is subclass of UIView.
class TouchHandlingView: UIControl {
}
And addTarget to it:
@IBOutlet weak var mainView: TouchHandlingView!
...
mainView.addTarget(self, action: "startAction:", forControlEvents: .TouchDown)
...
Then the designated action will be called like UIButton:
func startAction(sender: AnyObject) {
print("start")
}
Swift (without subclassing)
Here is a Swift version similar to Rob Caraway's Objective-C answer.
The idea is to use a long press gesture recognizer with the minimumPressDuration
set to zero rather than using a tap gesture recognizer. This is because the long press gesture recognizer reports touch began events while the tap gesture does not.
import UIKit
class ViewController: UIViewController {
@IBOutlet weak var myView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
// Add "long" press gesture recognizer
let tap = UILongPressGestureRecognizer(target: self, action: #selector(tapHandler))
tap.minimumPressDuration = 0
myView.addGestureRecognizer(tap)
}
// called by gesture recognizer
@objc func tapHandler(gesture: UITapGestureRecognizer) {
// handle touch down and touch up events separately
if gesture.state == .began {
// do something...
print("tap down")
} else if gesture.state == .ended { // optional for touch up event catching
// do something else...
print("tap up")
}
}
}