Question

I’m trying to animate (fade in/out) a UILabel and I’m using the following code:

float newAlpha = 0.0;

//TODO:Check if the previous animation has finished

if(answer.alpha==0.0) {
    newAlpha = 1.0;
} else if(answer.alpha==1.0) {
    newAlpha = 0.0;
}
[UIView animateWithDuration:1.0 animations:^{
    answer.alpha = newAlpha;
}];

Where the TODO comment is, I want to check if the previous animation has finished and if it hasn’t, exit the method. Is there some way of doing this?

Answer 1

UPDATE #1:

you need a variable in your class:

BOOL _animationFinished;

and then you can use the following way for the animation:

float newAlpha = 0.0;

//TODO:Check if the previous animation has finished
if (_animationFinished == false) return;

if(answer.alpha==0.0) {
    newAlpha = 1.0;
} else if(answer.alpha==1.0) {
    newAlpha = 0.0;
}

[UIView animateWithDuration:1.0f animations:^{ answer.alpha = newAlpha; _animationFinished = false; } completion:^(BOOL finished){ _animationFinished = true; }];

it must be work.

---

ORIGINAL

I’m always checking the subject of the animation in this case, like this:

float newAlpha = 0.0;

//TODO:Check if the previous animation has finished
if (answer.alpha > 0.f || answer.alpha < 1.f) return; // it is always good enough for me
// ...or with AND it will cause the same effect:
// if (answer.alpha > 0.f && answer.alpha < 1.f) return;

if(answer.alpha==0.0) {
    newAlpha = 1.0;
} else if(answer.alpha==1.0) {
    newAlpha = 0.0;
}
[UIView animateWithDuration:1.0 animations:^{
    answer.alpha = newAlpha;
}];