objective-c Shaking

gistfile1.m

static BOOL AccelerationIsShaking(UIAcceleration* last, UIAcceleration* current, double threshold) {
	double
	deltaX = fabs(last.x - current.x),
	deltaY = fabs(last.y - current.y),
	deltaZ = fabs(last.z - current.z);
	
	return
	(deltaX > threshold && deltaY > threshold) ||
	(deltaX > threshold && deltaZ > threshold) ||
	(deltaY > threshold && deltaZ > threshold)
	;
}

- (void) accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
	if (self.lastAcceleration) {
		if (AccelerationIsShaking(self.lastAcceleration, acceleration, 0.9)) {
			histeresisExcited = YES;
			/* SHAKE DETECTED. DO HERE WHAT YOU WANT. */
           

			NSLog(@"start");
		} else if (histeresisExcited && !AccelerationIsShaking(self.lastAcceleration, acceleration, 0.03)) {

                   histeresisExcited = NO;
          NSLog(@"end");
		}
	}
	self.lastAcceleration = acceleration;
}