IOS indexPathsForVisibleItems原理

通过对UICollectionView的滑动 打印

NSArray *cellIndices = [self.collectionViewindexPathsForVisibleItems];

NSLog(@"%@",cellIndices);

结果：1.

(

    "<NSIndexPath: 0xc000000000000016> {length = 2, path = 0 - 0}"

)

2.

(

    "<NSIndexPath: 0xc000000000000016> {length = 2, path = 0 - 0}",

    "<NSIndexPath: 0xc000000000000056> {length = 2, path = 1 - 0}"

)

3.

(

    "<NSIndexPath: 0xc000000000000096> {length = 2, path = 2 - 0}",

    "<NSIndexPath: 0xc000000000000056> {length = 2, path = 1 - 0}"

)

4.

(

    "<NSIndexPath: 0xc000000000000096> {length = 2, path = 2 - 0}",

    "<NSIndexPath: 0xc0000000000000d6> {length = 2, path = 3 - 0}"

)

5.

(

    "<NSIndexPath: 0xc0000000000000d6> {length = 2, path = 4 - 0}"

    "<NSIndexPath: 0xc0000000000000d6> {length = 2, path = 3 - 0}"

)

6.

(

    "<NSIndexPath: 0xc0000000000000d6> {length = 2, path = 4 - 0}"

    "<NSIndexPath: 0xc0000000000000d6> {length = 2, path = 5 - 0}"

)

......

结论：系统对可见cell的复用原理是替换原先的旧值,这里我们就必须特殊的使用这个复用数组。