层是什么有益的？添加图层怎么办？为什么要考虑图层？ [英] What are Layers good for? What could I do with adding an Layer, and why should I think about Layers?

问题描述

我想知道是什么让Layers与Views不同，当每个View都带有它自己的Layer时。也许我错了。但那么：这些图层有什么用呢？

I am wondering what makes Layers different from Views, when every View comes along with it's own Layer. Maybe I am wrong with that. But then: What are these Layers good for?

就像我理解的那样，我会使用UIView在GUI中对元素进行分组。我也可以使用UIView来定位其他东西。那么Layers到底在哪里？

Like I understand it, I would use an UIView to group elements in my GUI. I could also use that UIView to position things over other things. So where come Layers into place here?

我是否应该像在HTML / CSS中那样将它们视为z-index？它们对核心动画的东西有用吗？

Should I think of them just as the z-index like in HTML / CSS? Are they just interesting for Core Animation stuff?

推荐答案

与UIVIews相比，CALayers

Compared to UIVIews, CALayers are

• 轻量级


• 充满了动画的时间信息


• 有些东西比文字更难画（尤其是unicode）。

如果你的数量少于20个，那可能无关紧要。如果您有复杂的动画需求，或只需要绘制大量图层，您可能会因使用CALayers而受益。

If you have less than 20 or so of them, it probably doesn't matter. If you have complicated animation needs, or just a ton of layers to draw, you may benefit from using CALayers instead.

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