如何依次链接不同层的核心动画？ [英] How can I chain Core Animations for different Layers one after the other?

问题描述

我有一个启用了页面调度的scrollView和N个页面，它们是UIViews作为scrollView的子视图。

我正在尝试执行以下操作：

用户滚动到第n页。
此时，先前添加到页面编号n
（即，页面[[scrollView子视图] objectAtIndex：n-1] .layer subLayers]）中的7个CALayer淡入，在其他。

但是我不知道如何依次使CALayers淡入。到目前为止，我已经尝试了以下3种方法来实现我的控制器的委托方法： b $ b（假设我对图层有一个数组，并且在创建时将其不透明度设置为0）

 -（无效）scrollViewDidEndDecelerating：（UIScrollView *）scrollView 
 {
 int pageNumber = floor（self.scrollView.contentOffset.x / self.scrollView.frame.size.width）; 
 if（pageNumber ==（n-1））
 {
 int timeOffset = 0; 
 
 [CATransaction开始]; 
 for（CALayer * layerArray的图层）
 {
 CABasicAnimation * a = [CABasicAnimation animationWithKeyPath：@ opacity]; 
 a.duration = 6; 
 a.beginTime = timeOffset ++; 
 a.fromValue = [NSNumber numberWithFloat：0。]； 
 a.toValue = [NSNumber numberWithFloat：1。]； 
 
 [layer addAnimation：a forKey：nil]; 
} 
 [CATransaction commit]; 
} 
} 
 
-（void）scrollViewDidEndDecelerating：（UIScrollView *）scrollView 
 {
 int pageNumber = floor（self.scrollView.contentOffset.x / self.scrollView.frame.size.width）; 
 if（pageNumber ==（n-1））
 {
 int timeOffset = 0; 
 
 [CATransaction开始]; 
 for（CALayer * layerArray的图层）
 {
 CABasicAnimation * a = [CABasicAnimation animation]; 
 a.duration = 6; 
 a.beginTime = timeOffset ++; 
 [layer addAnimation：a forKey：@ opacity]； 
 [layer setOpacity：1]; 
} 
 [CATransaction commit]; 
} 
} 
 
 
-（void）scrollViewDidEndDecelerating：（UIScrollView *）scrollView 
 {
 int pageNumber = floor（self.scrollView .contentOffset.x / self.scrollView.frame.size.width）; 
 if（pageNumber ==（n-1））
 {
 int timeOffset = 0; 
 
 
 for（CALayer * layerArray中的图层）
 {
 [CATransaction begin]; 
 CABasicAnimation * a = [CABasicAnimation动画]; 
 a.duration = 6; 
 a.beginTime = timeOffset ++; 
 [layer addAnimation：a forKey：@ opacity]； 
 [layer setOpacity：1]; 
} 
 
 for（CALayer * layerArray中的图层）
 [CATransaction commit]; 
} 
} 
  

但似乎都不起作用。当用户滚动到正确的页面时，所有层都立即可见，没有太多的褪色，而且绝对没有任何顺序。

有什么想法吗？

解决方案

实际上，事实证明，关键是根据参考系获取当前时间，并向该当前时间添加任何时间偏移量时间。

例如，这段代码中的某些内容将导致n层（假定存储在某个数组中）依次淡入淡出。

  CGFloat timeOffset = 0; 
 
 [CATransaction开始]; 
 
 for（CALayer * layers in layer）{
 CABasicAnimation * a = [CABasicAnimation animationWithKeyPath：@ opacity]; 
 
 a.fromValue = @（0）; 
 a.toValue = @（1）; 
 a.fillMode = kCAFillModeForwards; 
 a.beginTime = [layerLayerTime：CACurrentMediaTime（）fromLayer：nil] + timeOffset; 
 a.duration = 0.8; 
 a.removedOnCompletion =否； 
 
 [layer addAnimation：a forKey：nil]; 
 
 timeOffset + = a.duration; 
} 
 
 [CATransaction commit]; 
  

在上述情况下，参照系只是调用发生的当前时间。 / p>

I have a scrollView with paging enabled and a number N of pages, which are UIViews as subviews of the scrollView.

I'm trying to do the following:

User scrolls to page number n. At that point, 7 CALayers which were previously added to page number n (that is, to page [[scrollView subviews] objectAtIndex:n-1].layer subLayers]) fade in, one after the other.

But I can't figure out how to make the CALayers fadeIn sequentially.So far, I've tried the following 3 approaches from my controller's delegate method: (assume I have an array to the layers and that their opacity was set to 0 upon creation)

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
  int pageNumber = floor(self.scrollView.contentOffset.x / self.scrollView.frame.size.width);
  if(pageNumber == (n-1))
  {
    int timeOffset = 0;

    [CATransaction begin];
    for(CALayer *layer in layerArray)
    {
      CABasicAnimation *a = [CABasicAnimation animationWithKeyPath:@"opacity"];
      a.duration = 6;
      a.beginTime = timeOffset++;
      a.fromValue = [NSNumber numberWithFloat:0.];
      a.toValue = [NSNumber numberWithFloat:1.];

      [layer addAnimation:a forKey:nil];
    }
    [CATransaction commit];
  }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
  int pageNumber = floor(self.scrollView.contentOffset.x / self.scrollView.frame.size.width);
  if(pageNumber == (n-1))
  {
    int timeOffset = 0;

    [CATransaction begin];
    for(CALayer *layer in layerArray)
    {
      CABasicAnimation *a = [CABasicAnimation animation];
      a.duration = 6;
      a.beginTime = timeOffset++;
      [layer addAnimation:a forKey:@"opacity"];
      [layer setOpacity:1];
    }
    [CATransaction commit];
  }
}


- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
  int pageNumber = floor(self.scrollView.contentOffset.x / self.scrollView.frame.size.width);
  if(pageNumber == (n-1))
  {
    int timeOffset = 0;


    for(CALayer *layer in layerArray)
    {
      [CATransaction begin];
      CABasicAnimation *a = [CABasicAnimation animation];
      a.duration = 6;
      a.beginTime = timeOffset++;
      [layer addAnimation:a forKey:@"opacity"];
      [layer setOpacity:1];
    }

    for(CALayer *layer in layerArray)
      [CATransaction commit];
  }
}

But neither seems to work. When the user scrolls to the right page, all layers become visible at once, without much of a fade and definitely not in any sequential order.

Any ideas?

解决方案

Actually, it turns out that the key is getting the current time in terms of a frame of reference and adding any time offset to that current time. This works also for non-grouped animations.

For instance, something along the lines of this code would cause n layers (assumed to be stored in some array) to sequentially fade in one after the other, each taking .8 secs.:

CGFloat timeOffset = 0;

[CATransaction begin];

for (CALayer *layer in layers) {
    CABasicAnimation *a = [CABasicAnimation animationWithKeyPath:@"opacity"];

    a.fromValue = @(0);
    a.toValue = @(1);
    a.fillMode = kCAFillModeForwards;
    a.beginTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil] + timeOffset;
    a.duration = 0.8;
    a.removedOnCompletion = NO;

    [layer addAnimation:a forKey:nil];

    timeOffset += a.duration;
}

[CATransaction commit];

In the above case, the frame of reference is simply the current time when the invocations take place.

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