UICollectionView的多选和取消

多选

首先要设置collectionView可以多选，默认是关闭的
collectionView.allowsMultipleSelection = YES;

设置选中item的状态(具体显示):

可以复写cell的setSelected方法

- (void)setSelected:(BOOL)selected {
    if (selected) {
         // your code
    } else {
        // your code
    }
}

也可以在

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];
    //your code
}

获取到选中cell，然后设置cell选中的样式

取消选中

通过 [collectionView indexPathsForSelectedItems]获取当前选中item数组，在- (BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath方法中判断选中数组是否包含indexPath：如果包含,进行取消选中操作

- (BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    if ([[collectionView indexPathsForSelectedItems] containsObject:indexPath]) {
        //取消选中 返回NO，这样collectionView就不会再调用didSelectItemAtIndexPath方法
        [collectionView deselectItemAtIndexPath:indexPath animated:YES];
        return NO;
    }
    return YES;
}