从可见的行列表中提取部分: NSArray *indexPathsForVisibleRows = [tableView indexPathsForVisibleRows];
NSMutableIndexSet *indexSet = [NSMutableIndexSet indexSet];
for ( NSIndexPath *indexPath in indexPathsForVisibleRows ) {
[indexSet addIndex:indexPath.section];
}
NSLog(@"indexSet %@",indexSet);
// indexSet