iphone development - UIRotationGestureRecognizer (Clockwise & counter Clockwise detection)?

问题

Is there a way to detect if the rotation done by the user is in clockwise or counter clockwise direct???

I searched for that but couldn't find an answer !

My code looks like this:

 UIGestureRecognizer *recognizer;
 recognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(spin)];
 [self.rotating addGestureRecognizer:recognizer];
 [recognizer release];

回答1:

the rotation property will tell you the rotation in radians. A negative value would indicate the rotation is clockwise, and a positive value indicates counter-clockwise.

Example:

UIGestureRecognizer *recognizer;
recognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(spin:)];  // <-- Note the colon after the method name
[self.rotating addGestureRecognizer:recognizer];
[recognizer release];

- (void)spin:(UIGestureRecognizer *)gestureRecognizer {
    CGFloat rotation = gestureRecognizer.rotation;
    if (rotation < 0) {
        // clockwise
    } else {
        // counter-clockwise
    }
}

回答2:

Swift version - imagine you've connected your UIRotationGestureRecognizer to an IBAction and are passing in the UIRotationGestureRecognizer as argument recognizer. You could very easily test direction with the following:

if recognizer.rotation < 0 {
    print("Negative rotation value means anticlockwise rotation detected")
} else if recognizer.rotation > 0 {
    print("Positive rotation value means clockwise rotation detected")
}

来源：https://stackoverflow.com/questions/6390457/iphone-development-uirotationgesturerecognizer-clockwise-counter-clockwise