为什么带有 UICollectionViewFlowLayout 的 UICollectionView 不显示单元格，而是询问大小? [英] Why UICollectionView with UICollectionViewFlowLayout not show cells, but ask for size?

问题描述

为什么带有流布局的 collectionview 有时不显示单元格，但委托要求大小，部分项目计数和响应者提供正确的信息.

Why collectionview with flow layout sometimes not showing cells, but delegate ask for size, and section items count and responder give correct information.

这里的例子，6节有问题

Here example, trouble with 6 section

2015-04-08 04:43:59.020 ASKED SECTION:0 ITEMS:0
2015-04-08 04:43:59.023 RETUR SECTION:0 ITEMS:1
2015-04-08 04:43:59.023 ASKED SECTION:1 ITEMS:0
2015-04-08 04:43:59.024 RETUR SECTION:1 ITEMS:1
2015-04-08 04:43:59.024 ASKED SECTION:2 ITEMS:0
2015-04-08 04:43:59.024 RETUR SECTION:2 ITEMS:1
2015-04-08 04:43:59.024 ASKED SECTION:3 ITEMS:0
2015-04-08 04:43:59.024 RETUR SECTION:3 ITEMS:1
2015-04-08 04:43:59.025 ASKED SECTION:4 ITEMS:0
2015-04-08 04:43:59.043 RETUR SECTION:4 ITEMS:0
2015-04-08 04:43:59.043 ASKED SECTION:5 ITEMS:0
2015-04-08 04:43:59.043 RETUR SECTION:5 ITEMS:0
**2015-04-08 04:43:59.043 ASKED SECTION:6 ITEMS:0**
**2015-04-08 04:43:59.044 RETUR SECTION:6 ITEMS:1**
2015-04-08 04:43:59.044 ASKED SECTION:7 ITEMS:0
2015-04-08 04:43:59.044 RETUR SECTION:7 ITEMS:8
2015-04-08 04:43:59.045 ASKED SECTION:8 ITEMS:0
2015-04-08 04:43:59.046 RETUR SECTION:8 ITEMS:0
2015-04-08 04:43:59.046 ASKED SECTION:9 ITEMS:0
2015-04-08 04:43:59.046 RETUR SECTION:9 ITEMS:2
2015-04-08 04:43:59.049 SIZE_ SECTION:0 ITEM:0 SIZE:320x70
2015-04-08 04:43:59.052 SIZE_ SECTION:1 ITEM:0 SIZE:320x70
2015-04-08 04:43:59.053 SIZE_ SECTION:2 ITEM:0 SIZE:320x0
2015-04-08 04:43:59.053 SIZE_ SECTION:3 ITEM:0 SIZE:320x246.1538
**2015-04-08 04:43:59.053 SIZE_ SECTION:6 ITEM:0 SIZE:320x80**
2015-04-08 04:43:59.055 SIZE_ SECTION:7 ITEM:0 SIZE:320x139
2015-04-08 04:43:59.057 SIZE_ SECTION:7 ITEM:1 SIZE:320x139
2015-04-08 04:43:59.062 SIZE_ SECTION:7 ITEM:2 SIZE:320x79
2015-04-08 04:43:59.066 SIZE_ SECTION:7 ITEM:3 SIZE:320x79
2015-04-08 04:43:59.069 SIZE_ SECTION:7 ITEM:4 SIZE:320x79
2015-04-08 04:43:59.072 SIZE_ SECTION:7 ITEM:5 SIZE:320x79
2015-04-08 04:43:59.075 SIZE_ SECTION:7 ITEM:6 SIZE:320x79
2015-04-08 04:43:59.079 SIZE_ SECTION:7 ITEM:7 SIZE:320x79
2015-04-08 04:43:59.079 SIZE_ SECTION:9 ITEM:0 SIZE:139x139
2015-04-08 04:43:59.080 SIZE_ SECTION:9 ITEM:1 SIZE:139x139
2015-04-08 04:43:59.082 CELL_ SECTION:0 ITEMS:0
2015-04-08 04:43:59.087 CELL_ SECTION:1 ITEMS:0

正如您在 numberOfItemsInSection (ASKED, RETUR) 中看到的，在 6 部分中返回了 1 个项目

As u can see in numberOfItemsInSection (ASKED, RETUR) returned 1 item in 6 section

2015-04-08 04:43:59.044 返回部分:6 项:1

之后在 sizeForItemAtIndexPath 中为 6 部分中的 0 个项目返回大小

After that in sizeForItemAtIndexPath for 0 item in 6 section returned size

2015-04-08 04:43:59.053 SIZE_SECTION:6 ITEM:0 SIZE:320x80

然后 collectionview 要求单元格，而不是第 6 节调用

But then collectionview ask for cell, not called for section 6

2015-04-08 04:43:59.082 CELL_ SECTION:0 ITEMS:0
2015-04-08 04:43:59.087 CELL_ SECTION:1 ITEMS:0

推荐答案

我找到了解决方案！

2015-04-08 04:43:59.053 SIZE_ SECTION:2 ITEM:0 SIZE:320x0

如果您看到您的单元格消失在它们必须可见的地方，请检查您的尺寸！

If u see what yours cell disappears where they must be visible, check your sizes!

如果有任何边框大小为零，则说明 CollectionViewFlowLayout 无法正常工作.

If any of border size will be a zero, it's broke correct working CollectionViewFlowLayout.

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