Detect when second tableview cell comes into view - then perform an action

I've got a UITableView in a UIViewController, as well as a filter button. I hide the filter button when the user starts to scroll down the list. I want to then show the filter button when the second cell (index 1) is visible. However, I can't get this desired effect, I can only get it to appear when it reaches the top. Here is my code for when it reaches the top (I then show the filter button again).

//determines when the tableview was scrolled
-(void) scrollViewDidScroll:(UIScrollView *)scrollView
{
    CGPoint currentOffset = scrollView.contentOffset;
     //tableview is scrolled down
    if (currentOffset.y > self.lastContentOffset.y)
      {

    //if the showFilter button is visible i.e alpha is greater than 0
        if (self.showFilter.alpha==1.0) {

            [UIView animateWithDuration:1 animations:^{

                //hide show filter button
                self.showFilter.alpha=0.0;
                //I also adjust the frames of a tableview here
            }];

        }


    }


    //determines if it is scrolled back to the top
    if (self.showFilter.alpha==0.0 && currentOffset.y==0) {
        [UIView animateWithDuration:0.3 animations:^{
            //show filter button
            self.showFilter.alpha=1.0;

          //i also adjust the frames of the tableview here
        }];
    }

    self.lastContentOffset = currentOffset;
}

I have also tried:

if (self.showFilter.alpha==0.0 && currentOffset.y<160)

But it doesn't work to the desired effect as the tableview jumps off the screen. Is there another way to get this desired effect?