滚动UITableview改变UIbutton的图片

有一个UITableView，然后添加了一个自定义视图作为UIButton。每个button都有一个tag，在动作方法中获取tag，当点击按钮时，会改变选中和取消按钮的图片，问题是，等到我滚动它时，又回复了正常状态。

这是索引方法中cell的行。

static NSString *CellIdentifier = @"Cell4";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
    cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];
}
followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
[followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];
[followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
[cell.contentView addSubview:followingButton];
NSLog(@"row--%d",indexPath.row);
followingButton.tag=indexPath.row;
NSLog(@"followingButton.tag--%d",followingButton.tag);
[self configureCellFollowing:cell forIndexPath:indexPath];
return cell;
}

==================

//Here is the action method

-(void)followingButtonpressed:(id)sender
{
    NSLog(@"sender tag --%d",[sender tag]);
    UIButton *btnPly = (UIButton *)sender;
    if([btnPly isSelected])
    {
        [btnPly setSelected:NO];
        [btnPly setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
    }
    else
    {
        [btnPly setSelected:YES];
        [btnPly setImage:[UIImage imageNamed:@"following_off12.png"] forState:UIControlStateNormal];
    }
}