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Hi,

I want to detect, what part of screen is touched, when user shakes iPhone.

I do it in the following way:

-(void) accelerometer: (UIAccelerometer*)accelerometer didAccelerate: (UIAcceleration*)acceleration
{
    float shakeStrength = sqrt( acceleration.x * acceleration.x + acceleration.y * acceleration.y + acceleration.z * acceleration.z );

    if (shakeStrength >= 1.5f)
    {
     if (isLeftHandTouches && isRightHandTouches)
     {
      DebugLog(@"both hands shake");
     } else if (isLeftHandTouches)
     {
      DebugLog(@"left hand shake");
     } else if (isRightHandTouches)
     {
      DebugLog(@"right hand shake");
     }
    }
}

-(void) touchesBegan: (NSSet *)touches withEvent: (UIEvent *)event
{
    NSSet *allTouches = [event allTouches];

    for (int i = 0; i < [allTouches count]; i++)
    {
     if ([ [ [allTouches allObjects] objectAtIndex: i] locationInView: [self view] ].x <= 240.0f)
     {
      isLeftHandTouches = YES;
     } else
     {
      isRightHandTouches = YES;
     }
    }
}

-(void) touchesEnded: (NSSet *)touches withEvent: (UIEvent *)event
{
    NSSet *allTouches = [event allTouches];

    for (int i = 0; i < [allTouches count]; i++)
    {
     if ([ [ [allTouches allObjects] objectAtIndex: i] locationInView: [self view] ].x <= 240.0f)
     {
      isLeftHandTouches = NO;
     } else
     {
      isRightHandTouches = NO;
     }
    }
}

Everything works fine if user removes both hands before making another shake, but everything gets messed up if I have both hands on the screen and remove one of them.

i.e. I shake with both hands on the screen and afterwards I want to shake the iPhone with only one hand. In this case the shake won't count - as if there no touches on the screen. I assume that when I remove one hand from the screen, both "touches" are being removed.

What is the problem and how can I fix it?

Thanks.

Answer 1

Why are you enumerating over -allTouches? Just enumerate over the touches set that is passed in. The same goes for both methods.