如何链接淡出动画

Question

我有3个UILabels ，我想在几秒钟后一个接一个地淡出。 我的问题是这些都是一下子发生的。 我试图链接动画，但我不能让它工作。 我尝试了各种各样的建议，但无济于事。 我知道这不可能很难。 我最好想在一个动画方法中将它们捆绑在一起，因为我想在显示所有3个标签后从animationDidStop触发其他功能。 任何帮助或建议？

这是我的代码：

- (void)viewDidLoad
{
    [self fadeAnimation:@"fadeAnimation" finished:YES target:lblReady];
    [self fadeAnimation:@"fadeAnimation" finished:YES target:lblSet];
    [self fadeAnimation:@"fadeAnimation" finished:YES target:lblGo];
}


- (void)fadeAnimation:(NSString *)animationID finished:(BOOL)finished target:(UIView *)target
{
    [UIView beginAnimations:nil context:nil];
    [UIView beginAnimations:animationID context:(__bridge void *)(target)];
    [UIView setAnimationDuration:2];

    [target setAlpha:0.0f];
    [UIView setAnimationDelegate:self];    
    [UIView commitAnimations];
}

Answer 1

使用最新的UIView动画方法会更容易：

[UIView animateWithDuration:2.0 animations:^ {
    lblReady.alpha = 0;
} completion:^(BOOL finished) {
    [UIView animateWithDuration:2.0 animations:^ {
        lblSet.alpha = 0;
    } completion:^(BOOL finished) {
        [UIView animateWithDuration:2.0 animations:^ {
            lblGo.alpha = 0;
        } completion:^(BOOL finished) {
            // Add your final post-animation code here
        }];
    }];
}];

Answer 2

你应该让他们执行performSelector：withObject：afterDelay：而不是。

所以将代码更改为：

- (void)viewDidLoad
{
    [self performSelector:@selector(fadeAnimation:) withObject:lblReady afterDelay:0];
    [self performSelector:@selector(fadeAnimation:) withObject:lblSet afterDelay:2];
    [self performSelector:@selector(fadeAnimation:) withObject:lblGo afterDelay:4];
}

-(void)fadeAnimation:(UIView *)target {
    [self fadeAnimation:@"fadeAnimation finished:YES target:target];
}




- (void)fadeAnimation:(NSString *)animationID finished:(BOOL)finished target:(UIView *)target
{
    [UIView beginAnimations:nil context:nil];
    [UIView beginAnimations:animationID context:(__bridge void *)(target)];
    [UIView setAnimationDuration:2];

    [target setAlpha:0.0f];
    [UIView setAnimationDelegate:self];    
    [UIView commitAnimations];
}

这只是在0,2或4个部分之后调用每个动作代码。 如果更改动画持续时间，则应相应地更改这些数字。

如果您想使用块动画而不是使用旧动画样式，您可以改为：

[UIView animateWithDuration:2 animations ^{
    //put your animations in here
} completion ^(BOOL finished) {
    //put anything that happens after animations are done in here.
    //could be another animation block to chain animations
}];