如何使用UIPinchGestureRecognizer检测或定义捏合手势的方向？

Question

我正在使用UIPinchGestureRecognizer来检测捏捏手势，例如：

- (void) initPinchRecon {
 UIPinchGestureRecognizer *pinchRecognizer = [[[UIPinchGestureRecognizer alloc] 
              initWithTarget:self
              action:@selector(Perform_Pinch:)] autorelease];
 [self addGestureRecognizer:pinchRecognizer];

 [pinchRecognizer setScale:20.0f];
}

- (void) Perform_Pinch:(UIPinchGestureRecognizer*)sender{
 NSLog(@"PINCH");
} 

并且可以很好地检测简单的捏合手势：可以确定（或定义自己）捏合手势的角度或方向？例如，区分水平捏合手势和垂直捏合手势？

Answer 1

一个非常简单的解决方案是像这样实现手势处理程序：

-(void)handlePinchGesture:(UIPinchGestureRecognizer *)recognizer {
if (recognizer.state != UIGestureRecognizerStateCancelled) {
    if (recognizer.numberOfTouches == 2) {
        CGPoint firstPoint = [recognizer locationOfTouch:0 inView:recognizer.view];
        CGPoint secondPoint = [recognizer locationOfTouch:1 inView:recognizer.view];

        CGFloat angle = atan2(secondPoint.y - firstPoint.y, secondPoint.x - firstPoint.x);

        // handle the gesture based on the angle (in radians)
    }
}