Question

I cannot figure out what is wrong. Below is my code, and it calls the delegate methods once then stops.

What should I do? I haven;t been able to find the sample code that uses these delegate methods. All I’ve found were gesture recognizers for swipes and taps, using different delegates.

Code so far:

-(void)initTouchesRecognizer{

    DLog(@"");

    recognizer = [[UIGestureRecognizer alloc] init];

    [self addGestureRecognizer:recognizer];

}


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


    DLog(@"");


    NSSet *allTouches = [event allTouches];
    for (UITouch *touch in allTouches)
    {


    }

}




-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event allTouches] anyObject];
    CGPoint location = [touch locationInView:touch.view];

}




- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
       DLog(@"");

}



- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    [self touchesEnded:touches withEvent:event];
}

I call initTouchesRecognizer from initwithrect for my image view.

What am i doing fundamentally wrong?

Answer 1

UIGestureRecognizer is an abstract class, you’re not supposed to add it directly to your view. You need to use a concrete subclass that inherits from UIGestureRecognizer, like UITapGestureRecognizer or UIPanGestureRecognizer for example. You could also make your own concrete subclass but that usually isn’t necessary.

Here is an example of adding a UIPanGestureRecognizer to your view (in your view class code, often the gesture is added to the view from the controller):

UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(mySelector:)];
[self addGestureRecognizer:panGesture];

In this case, the selector will be called when ever the user pans in this view. If you added a UITapGestureRecognizer, the selector would be called when the user tapped.

You can check out the apple docs for more info:
http://developer.apple.com/library/ios/#documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/GestureRecognizer_basics/GestureRecognizer_basics.html#//apple_ref/doc/uid/TP40009541-CH2-SW2

Also, I find Paul Hagerty’s Stanford lectures to be great, here’s one on gesture recognizers:
https://itunes.apple.com/ca/course/6.-views-gestures-january/id593208016?i=132123597&mt=2

You should also understand that none of the methods that you posted are delegate methods, and none of them have anything to do with the UIGestureRecognizer that you added in your code. Those are instance methods of UIResponder (a class that UIView inherits from) that you’re overriding. The abstract UIGestureRecognizer also has instance methods with those same names, but it is not the UIGestureRecognizer methods that are getting called in your class.