Question

Has anyone managed to get the gesture recognition working in cocos-2d?

I have read a post here that claimed to have achieved it, here: http://www.cocos2d-iphone.org/forum/topic/8929

I patched from the git hub here: https://github.com/xemus/cocos2d-GestureRecognizers/blob/master/README

I made a subclass of CCSprite (which is a subclass of CCNode):

-(id) initWithTexture:(CCTexture2D*)texture rect:(CGRect)rect {
if( (self=[super initWithTexture:texture rect:rect]) )
{
    CCGestureRecognizer* recognizer;
    recognizer = [CCGestureRecognizer 
        CCRecognizerWithRecognizerTargetAction:[[[UITapGestureRecognizer alloc]init] autorelease] 
                  target:self 
                  action:@selector(tap:node:)];
    [self addGestureRecognizer:recognizer];
}
return self;
}

Delegate method:

- (void) swipe:(UIGestureRecognizer*)recognizer node:(CCNode*)node
{
NSLog(@" I never get called :( ");
}

My tap event never gets called.

Has anyone got this working? How difficult is it to do gesture recognition manually for swipe detection?

Answer 1

You need to attach the gesture recognizer to something “up the chain”. Don’t attach them to the individual nodes; attach them to the UIView (i.e., [[CCDirector sharedDirector] openGLView]).

Here’s what I did:

- (UIPanGestureRecognizer *)watchForPan:(SEL)selector number:(int)tapsRequired {
    UIPanGestureRecognizer *recognizer = [[[UIPanGestureRecognizer alloc] initWithTarget:self action:selector] autorelease];
    recognizer.minimumNumberOfTouches = tapsRequired;
    [[[CCDirector sharedDirector] openGLView] addGestureRecognizer:recognizer];
    return recognizer;
}

- (void)unwatch:(UIGestureRecognizer *)gr {
    [[[CCDirector sharedDirector] openGLView] removeGestureRecognizer:gr];
}

This particular code is used in a superclass for scene controllers, so the target for the selector is hard-coded to “self”, but you could easily abstract that to a passed-in object. Also, you could extrapolate the above to easily create gesture recognizers for taps, pinches, etc.

In the subclass for the controller, then, I just do this:

- (MyController *)init {
    if ((self = [super init])) {
        [self watchForPan:@selector(panning:) number:1];
    }
    return self;
}

- (void)panning:(UIPanGestureRecognizer *)recognizer {

    CGPoint p;
    CGPoint v;

    switch( recognizer.state ) {
        case UIGestureRecognizerStatePossible:
        case UIGestureRecognizerStateBegan:
            p = [recognizer locationInView:[CCDirector sharedDirector].openGLView];
            (do something when the pan begins)
            break;
        case UIGestureRecognizerStateChanged:
            p = [recognizer locationInView:[CCDirector sharedDirector].openGLView];
            (do something while the pan is in progress)
            break;
        case UIGestureRecognizerStateFailed:
            break;
        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateCancelled:
            (do something when the pan ends)
            (the below gets the velocity; good for letting player "fling" things)
            v = [recognizer velocityInView:[CCDirector sharedDirector].openGLView];
            break;
    }

}