How do I detect when someone shakes an iPhone?

Question

I want to react when somebody shakes the iPhone. I don\'t particularly care how they shake it, just that it was waved vigorously about for a split second. Does anyone know h

Answer 1

I came across this post looking for a "shaking" implementation. millenomi's answer worked well for me, although i was looking for something that required a bit more "shaking action" to trigger. I've replaced to Boolean value with an int shakeCount. I also reimplemented the L0AccelerationIsShaking() method in Objective-C. You can tweak the ammount of shaking required by tweaking the ammount added to shakeCount. I'm not sure i've found the optimal values yet, but it seems to be working well so far. Hope this helps someone:

- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
    if (self.lastAcceleration) {
        if ([self AccelerationIsShakingLast:self.lastAcceleration current:acceleration threshold:0.7] && shakeCount >= 9) {
            //Shaking here, DO stuff.
            shakeCount = 0;
        } else if ([self AccelerationIsShakingLast:self.lastAcceleration current:acceleration threshold:0.7]) {
            shakeCount = shakeCount + 5;
        }else if (![self AccelerationIsShakingLast:self.lastAcceleration current:acceleration threshold:0.2]) {
            if (shakeCount > 0) {
                shakeCount--;
            }
        }
    }
    self.lastAcceleration = acceleration;
}

- (BOOL) AccelerationIsShakingLast:(UIAcceleration *)last current:(UIAcceleration *)current threshold:(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);
}

PS: I've set the update interval to 1/15th of a second.

[[UIAccelerometer sharedAccelerometer] setUpdateInterval:(1.0 / 15)];