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

Simply changing the X coordinate of the center property of your view might do the trick. If you haven't done any core animation before it's pretty straight-forward.

First, start an animation right, then listen for it to finish, and then move back to the left, and so on. Getting the timing down so it "feels right" might take a while.

- (void)animationFinishCallback:(NSString *)animationID finished:(BOOL)finished context:(void *)context
{
  if ([animationID isEqualToString:@"MoveRight"]) {
    [UIView beginAnimations:@"MoveLeft" context:NULL];
    [UIView setAnimationDuration:1.0];
    [UIView setAnimationDelay: UIViewAnimationCurveEaseIn];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDidStopSelector:@selector(animationFinishCallback:finished:context:)];

    myView.center = CGRectMake(newX, newY);
    [UIView commitAnimations];
  }
}