Shake visual effect on iPhone (NOT shaking the device)

Question

On login failure, I\'d prefer to avoid showing an alert, it\'s too fleeting. Showing the alert and then showing the text somewhere on the login screen seems like duplication

Answer 1

I had seen some wobble animation and changed it to shake a view t pixels upright and downleft:

- (void)earthquake:(UIView*)itemView
{
    CGFloat t = 2.0;

    CGAffineTransform leftQuake  = CGAffineTransformTranslate(CGAffineTransformIdentity, t, -t);
    CGAffineTransform rightQuake = CGAffineTransformTranslate(CGAffineTransformIdentity, -t, t);

    itemView.transform = leftQuake;  // starting point

    [UIView beginAnimations:@"earthquake" context:itemView];
    [UIView setAnimationRepeatAutoreverses:YES]; // important
    [UIView setAnimationRepeatCount:5];
    [UIView setAnimationDuration:0.07];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDidStopSelector:@selector(earthquakeEnded:finished:context:)];

    itemView.transform = rightQuake; // end here & auto-reverse

    [UIView commitAnimations];
}

- (void)earthquakeEnded:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context 
{
    if ([finished boolValue]) 
    {
        UIView* item = (UIView *)context;
        item.transform = CGAffineTransformIdentity;
    }
}