iOS 10 UILabels - > 1 UIView - >使用动画循环播放

Question

我有10个UILabels,也许有些UIImageViews.我希望用1个UIView接一个的平滑FadeOut和FadeIn过渡显示所有这些.

我知道将UIView动画放在for循环中将不起作用,因为动画是异步完成的,并且不会产生适当的效果.所以我通常这样做的方法是将UIView动画链接在一起.即在一个元素动画完成后开始下一个.对于3-4个元素,代码看起来没问题.像这样 -

[UIView animateWithDuration:0.25 
                      delay:0 
                    options:UIViewAnimationCurveEaseInOut 
                 animations:^{ //do something with alpha here - first element } 
                 completion:^(BOOL finished){ 
                     [UIView animateWithDuration:0.25 
                             delay:0 
                             options:UIViewAnimationCurveEaseInOut 
                             animations:^{ //do something with alpha here - 2nd element} 
                                      completion:^(BOOL finished){ ... }

                 }

但对于10多个元素,它会变得非常混乱.怎么会这样做呢？基本上我正在创建一个UIView循环内容,就像一个小部件.

Answer 1

编辑NSTimer而不是循环.

counter 是标题中定义的ivar.

 - (void)viewDidLoad
{
    [super viewDidLoad];
    counter = 0;
    [NSTimer scheduledTimerWithTimeInterval:0.30
                                     target:self
                                   selector:@selector(timerTick:)
                                   userInfo:nil
                                    repeats:YES];
}

- (void) timerTick:(NSTimer *)timer{

    UIView *currentView = [self.view.subviews objectAtIndex:counter];
    [UIView animateWithDuration:0.25 
                          delay:0 
                        options:UIViewAnimationCurveEaseInOut 
                     animations:^{ currentView.alpha = 1.0;}
                     completion:^(BOOL finished){
                         [UIView animateWithDuration:0.25 animations:^{currentView.alpha = 0.0;}];
                     }
    ];
    counter++;
    if (counter >= [self.view.subviews count]) {
        counter = 0;
    }
}