UICollectionView 不遵守 UICollectionViewLayoutAttributes 的 zIndex [英] UICollectionView not obeying zIndex of UICollectionViewLayoutAttributes

问题描述

我想要达到的效果是一种粘性标题单元格.粘性细胞漂浮在其他细胞的顶部对我来说很重要.有点像这样:

The effect I'm trying to achieve is a kind of sticky header cell. It's important to me that the sticky cell floats over the top of the others. Something a bit like this:

┌──────────┐ 
│          │ 
│  Cell 0  │ 
│          ├┐
└┬─────────┘│
 │  Cell 4  │
 │          │
 └──────────┘
 ┌──────────┐
 │          │
 │  Cell 5  │
 │          │
 └──────────┘
 ┌──────────┐
 │          │
 │  Cell 6  │
 │          │
 └──────────┘

单元格 4、5 和 6 通常是可见的，我正在 layoutAttributesForElementsInRect: 期间在我的 UICollectionViewFlowLayout 子类中构建单元格 0 的属性.我所做的就是调用超级实现，确定需要添加的单元格，然后构造UICollectionViewLayoutAttributes(forCellWithIndexPath:).然后我将它的 zIndex 设置为 1(默认为 0).

Cell 4, 5 and 6 would normally viewable and I'm constructing the attributes for cell 0 in my UICollectionViewFlowLayout subclass during layoutAttributesForElementsInRect:. All I do is call the super implementation, determine which cell I need to add in and then construct the UICollectionViewLayoutAttributes(forCellWithIndexPath:). I then set the zIndex for it to 1 (default is 0).

我遇到的问题是 UICollectionView 似乎总是忽略 zIndex

The problem I'm getting is that the UICollectionView seems to always ignore the zIndex

┌──────────┐ 
│          │ 
│  Cell 0  │ 
│┌─────────┴┐
└┤          │
 │  Cell 4  │
 │          │
 └──────────┘
 ┌──────────┐
 │          │
 │  Cell 5  │
 │          │
 └──────────┘
 ┌──────────┐
 │          │
 │  Cell 6  │
 │          │
 └──────────┘

现在我相信可以使用 3d 变换在视觉上对此进行排序，但这对我不起作用，因为我不希望任何点击进入顶部的单元格.因此，在此示例中，我不希望 Cell 4 接收针对 Cell 0 的抽头.

Now I believe it's possible to visually sort this out using a 3d transform, but that doesn't work for me as I don't want any taps going to the cell which is over the top. So in this example I don't want Cell 4 receiving taps intended for Cell 0.

有人有什么想法吗?这是在 iOS 8.4 上.

Does anyone have any ideas? This is on iOS 8.4.

推荐答案

我做了一个独立的项目，以去除我所有的无关代码.在这个过程中，我想我找到了自己的解决方案.

I made a standalone project in order to strip out all my extraneous code. In the process I think I found my own solution.

override func initialLayoutAttributesForAppearingItemAtIndexPath(itemIndexPath: NSIndexPath) ->UICollectionViewLayoutAttributes?
和
override func finalLayoutAttributesForDisappearingItemAtIndexPath(itemIndexPath: NSIndexPath) ->UICollectionViewLayoutAttributes?

也没有应用新的 zIndex 所以我认为这是导致它的原因.

were not also applying the new zIndex so I think this was what was causing it.

只是想我应该发回解决方案，以防在搜索其他人时出现这种情况.

Just thought I should post back the solution in case this comes up in a search for anyone else.

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