iOS Motion Detection: Motion Detection Sensitivity Levels

Question

I have a simple question. I'm trying to detect when a user shakes the iPhone. I have the standard code in place to detect the motion and this works no problem. However, in testing this on my actual phone, I've realized that you have to shake the device quite hard to get the motion detection to trigger. I would like to know if there is a way to implement a level of sensitivity checking. For example, a way to detect if a user lightly shakes the device or somewhere between light and hard shake. This will be targeted towards iOS 7 so any tips or advice that is not deprecated from older iOS version would be greatly appreciated. I've done my googling but have yet to find any good solutions to this problem (If there are any.)

Thanks!

-(void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event
{
    if(motion == UIEventSubtypeMotionShake)
    {
       //Detected motion, do something about it 
       //at this point.
    }
}

-(BOOL)canBecomeFirstResponder
{
    return YES;
}

-(void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    [self becomeFirstResponder];
}

-(void)viewWillDisappear:(BOOL)animated
{
    [self resignFirstResponder];
    [super viewWillDisappear:animated];
}

Answer 1

Here is the solution I found. This works well but you do have to play with the deviceMotionUpdateInterval time value as well as the accelerationThreshold which can be tricky to get a fine balancing act for a actual "light shake" vs "picking up the phone and moving it closer to your face etc..." There might be better ways but here is one to start. Inside of my view didLoad I did something like this:

#import <CoreMotion/CoreMotion.h> //do not forget to link the CoreMotion framework to your project
#define accelerationThreshold  0.30 // or whatever is appropriate - play around with different values

-(void)viewDidLoad
{
      CMMotionManager *motionManager; 

      motionManager = [[CMMotionManager alloc] init];
      motionManager.deviceMotionUpdateInterval = 1;

      [motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue]  withHandler:^(CMDeviceMotion *motion, NSError *error)
             {
                [self motionMethod:motion];
             }];
}

-(void)motionMethod:(CMDeviceMotion *)deviceMotion
{
    CMAcceleration userAcceleration = deviceMotion.userAcceleration;
    if (fabs(userAcceleration.x) > accelerationThreshold
        || fabs(userAcceleration.y) > accelerationThreshold
        || fabs(userAcceleration.z) > accelerationThreshold)
        {
           //Motion detected, handle it with method calls or additional
           //logic here.
           [self foo];
        }
}