Getting the UITouch objects for a UIGestureRecognizer

Question

Is there a way to get the UITouch objects associated with a gesture? UIGestureRecognizer doesn't seem to have any methods for this.

Answer 1

Jay's right... you'll want a subclass. Try this one for size, it's from one of my projects. In DragGestureRecognizer.h:

@interface DragGestureRecognizer : UILongPressGestureRecognizer {

}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;

@end

@protocol DragGestureRecognizerDelegate <UIGestureRecognizerDelegate>
- (void) gestureRecognizer:(UIGestureRecognizer *)gr movedWithTouches:(NSSet*)touches andEvent:(UIEvent *)event;
@end

And in DragGestureRecognizer.m:

#import "DragGestureRecognizer.h"


@implementation DragGestureRecognizer

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    [super touchesMoved:touches withEvent:event];

    if ([self.delegate respondsToSelector:@selector(gestureRecognizer:movedWithTouches:andEvent:)]) {
        [(id)self.delegate gestureRecognizer:self movedWithTouches:touches andEvent:event];
    }

}

@end 

Of course, you'll need to implement the

- (void) gestureRecognizer:(UIGestureRecognizer *)gr movedWithTouches:(NSSet*)touches andEvent:(UIEvent *)event; 

method in your delegate -- for example:

DragGestureRecognizer * gr = [[DragGestureRecognizer alloc] initWithTarget:self action:@selector(pressed:)];
gr.minimumPressDuration = 0.15;
gr.delegate = self;
[self.view addGestureRecognizer:gr];
[gr release];



- (void) gestureRecognizer:(UIGestureRecognizer *)gr movedWithTouches:(NSSet*)touches andEvent:(UIEvent *)event{

    UITouch * touch = [touches anyObject];
    self.mTouchPoint = [touch locationInView:self.view];
    self.mFingerCount = [touches count];

}

Answer 2

If it is just the location you are interested in, you do not have to subclass, you will be notified of location changes of the tap from the UIGestureRecognizer.

Initialize with target:

self.longPressGestureRecognizer = [[[UILongPressGestureRecognizer alloc] initWithTarget: self action: @selector(handleGesture:)] autorelease];
[self.tableView addGestureRecognizer: longPressGestureRecognizer];

Handle UIGestureRecognizerStateChanged to get location changes:

- (void)handleGesture: (UIGestureRecognizer *)theGestureRecognizer {
    switch (theGestureRecognizer.state) {
        case UIGestureRecognizerStateBegan:
        case UIGestureRecognizerStateChanged:
        {
            CGPoint location = [theGestureRecognizer locationInView: self.tableView];

            [self infoForLocation: location];

            break;
        }

        case UIGestureRecognizerStateEnded:
        {
            NSLog(@"Ended");

            break;
        }

        default:
            break;
    }
}

Answer 3

If you only need to find out the location of the gesture, you can call either locationInView: or locationOfTouch:inView: on the UIGestureRecognizer object. However if you want to do anything else, then you'll need to subclass.

Answer 4

If you're writing your own UIGestureRecognizer you can get the touch objects overriding:

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

or the equivalent moved, ended or canceled

The Apple docs has lots of info on subclassing

Answer 5

Here is a method to get a long press added to an arbitrary UIView.

This lets you run longpress on any number of UIViews. In this example I restrict access to the UIView method through tags but you could use isKindOfClass as well.

(From what I found you have to use touchesMoved for LongPress because touchesBegan fires before the LongPress becomes active)

subclass - .h

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

            @interface MyLongPressGestureRecognizer : UILongPressGestureRecognizer

            - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;

            @property (nonatomic) CGPoint touchPoint;
            @property (strong, nonatomic) UIView* touchView;

            @end

subclass - .m

            #import "MyLongPress.h"

            @implementation MyLongPressGestureRecognizer

            - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
            {
                UITouch * touch = [touches anyObject];
                self.touchPoint = [touch locationInView:self.view];
                self.touchView  = [self.view hitTest:[touch locationInView:self.view] withEvent:event];
            }

            #pragma mark - Setters

            -(void) setTouchPoint:(CGPoint)touchPoint
            {
                _touchPoint =touchPoint;
            }

            -(void) setTouchView:(UIView*)touchView
            {
                _touchView=touchView;
            }
            @end

viewcontroller - .h

                           //nothing special here

viewcontroller - .m

            #import "ViewController.h"
            //LOAD
            #import "MyLongPress.h"

            @interface ViewController ()

            //lOAD
            @property (strong, nonatomic) MyLongPressGestureRecognizer* longPressGesture;

            @end

            @implementation PDViewController

            - (void)viewDidLoad
            {
                [super viewDidLoad];

                //LOAD
                self.longPressGesture =[[MyLongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressHandler:)];
                self.longPressGesture.minimumPressDuration = 1.2;
                [[self view] addGestureRecognizer:self.longPressGesture];
            }               

            //LOAD
            -(void) setLongPressGesture:(MyLongPressGestureRecognizer *)longPressGesture {
                _longPressGesture = longPressGesture;
            }

            - (void)longPressHandler:(MyLongPressGestureRecognizer *)recognizer {
                    if (self.longPressGesture.touchView.tag >= 100) /* arbitrary method for limiting tap */
                    {
                        //code goes here
                    }
            }

Answer 6

Simple and fast:

NSArray *touches = [recognizer valueForKey:@"touches"];

Where recognizer is your UIGestureRecognizer