Best method to get text to blink in iPhone OS?

Question

I want my text box to blink (like the old LCD clocks) and right now I'm calling a myriad of NSTimers and selectors that wait, change the alpha, wait, then change it back. Even with this it looks really bad, and I'm thinking I have to put an NSTimer to gradually change the alpha, but from what I hear they are not meant for things of that precision.

My thoughts are there must be a way to do this a lot better than how I am currently implementing it. It just feels like hax, you know.

Answer 1

NSTimers and changing the alpha is a perfectly acceptable way of doing it - that's certainly what I do. If you are having problems, perhaps a code sample might help us see where the issue is?

Answer 2

Using an animation delegate might make it less "hacky":

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];
[myLabel setAlpha:0.0];
[UIView commitAnimations];

And then you can have your didStopSelector restart the animation:

- (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {
    [self displayLabel];
}

Depending on the animationID, you could take different actions, etc. Using UIView's setAnimationDelay might come in handy as well.

UIView also has a setDuration call for animations:

[UIView setAnimationDuration:0.1];

If you are building for iOS4, check the documentation since you should be using block-based animation calls rather than these delegate based ones.

Answer 3

I would use an NSTimer, but instead of messing with alpha channels i would either not draw the text (if that's even possible with Apple's very attribute-limited SDK), or if that's not possible you could always draw something on top of it (like a rectangle).

Using this approach of drawing something over your text would yield better performance. Though some (okay most) would consider this a ugly hack, let me just say this, "If it looks right, it is right."