objective-c - 淡入淡出动画到uilabel

Question

我有一个要淡入然后淡出的标签。这是我的代码：

-(void) fadein
{
    scoreLabel.alpha = 0;
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
    [UIView setAnimationDuration:2];
    scoreLabel.alpha = 1;
    [UIView commitAnimations];
    [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];
}



-(void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished    context:(void *)context {
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:2];
 scoreLabel.alpha = 0;
[UIView commitAnimations];
}

从这段代码中我得到了这种情况：我的标签淡入，然后我看不到淡出动画。我该如何解决？

Answer 1

-(void) fadein
{
    scoreLabel.alpha = 0;
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseIn];

    //don't forget to add delegate.....
    [UIView setAnimationDelegate:self];

    [UIView setAnimationDuration:2];
    scoreLabel.alpha = 1;

    //also call this before commit animations......
    [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];
    [UIView commitAnimations];
}



-(void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished    context:(void *)context {
{
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:2];
    scoreLabel.alpha = 0;
    [UIView commitAnimations];
}

Answer 2

调用setAnimationDidStopSelector应该在提交动画之前：

[UIView beginAnimations:nil context:nil];
[UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
[UIView setAnimationDuration:2];
[UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];

scoreLabel.alpha = 1;

[UIView commitAnimations];