为什么带有UICollectionViewFlowLayout的UICollectionView不显示单元格，而是要求尺寸？

Question

为什么带有流布局的collectionview有时不显示单元格，而是委托人询问大小，并且节项目计数和响应者提供正确的信息。

这里的例子，麻烦6节

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

如您在numberOfItemsInSection（ASKED，RETUR）中所见，在6节中返回了1个项目

2015-04-08 04：43：59.044报废部分：6项目：1

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

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

但是然后collectionview询问单元格，而不是第6节

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

Answer 1

我找到了解决方案！

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

如果您看到必须看到的细胞消失了，请检查您的尺寸！

如果边框大小中的任何一个为零，则表示它无法正常工作CollectionViewFlowLayout。