Animating UILabel Fade In/Out

Question

I am going to end up with an array of RSS feeds, and would like a label or some such to display them at the bottom of the view. I would like to animate through each feed in the array.

This is what i have so far to animate, which, works for the fade, but only animates the last item of the array.

feed = [[UILabel alloc] initWithFrame:CGRectMake(0,380,320,43)];
[self.view addSubview:feed];

feed.alpha=1;

NSArray *feeds = [NSArray arrayWithObjects:[NSString stringWithFormat:@"1234567"],[NSString stringWithFormat:@"qwerty"],[NSString stringWithFormat:@"asdfgh"],nil];

for (NSString* f in feeds){

    feed.text=f;

    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
    [UIView setAnimationDuration:2.0f];
    feed.alpha=0;
    [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];
    [UIView commitAnimations];

}

Im sure its simple.

Thanks

Answer 1

First off you should really consider a better naming convention. Calling a UILabel a feed isn't very helpful for the future when you have to come back and look at your code. I would name it feedLabel. Then when you iterate through your list of feeds, you can just for (NSString *feed in feeds) and it will make more sense. And so will feedLabel.text = feed;.

Anyhow, the issue I see with your code is that your are repeatedly setting the alpha to zero in your loop, but you never set it back to one. In other words, you're not making a change to the alpha value. It stays the same in every iteration.

So maybe you could clarify what you're trying to do. If you want to fade the text between changes in the text, you'll need a different animation and methodology. Instead of a loop, chain your animations such that when your didStopSelector, you set the text and start the next one. Something like:

- (void)performAnimation;
{
  [UIView beginAnimations:nil context:NULL];
  [UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
  [UIView setAnimationDuration:2.0f];
  feed.alpha=0;
  [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:)];
  [UIView commitAnimations];
}

- (void)animationDidStop:(CAAnimation *)theAnimation finished:(BOOL)flag
{
  feed.alpha = 1.0;
  NSString *nextFeed = [self getNextFeed]; // Need to implement getNextFeed
  if (nextFeed)
  {
    // Only continue if there is a next feed.
    [feed setText:nextFeed];
    [self performAnimation];
  }
}

Answer 2

i tried your code, it fades out on first feed, but it doesn't enter the animationDidStop event. thats why it cant call performAnimation again. is there any set for animation (delegate or protocol etc..)