如何依次链接不同层的核心动画？

本文介绍了如何依次链接不同层的核心动画？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 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.