UIPageControl showing incorrect page - ios

Question

I've got a UIScrollView containing several tables, and a UIPageControl keeping track of which page the user is currently viewing. It works fine UNTIL i start scrolling up on the tableview, at which point the UIPageControl adjusts and says (incorrectly) that we are on the first page.
Here is my code:
- (void)scrollViewDidScroll:(UIScrollView *)_scrollView {
if (pageControlIsChangingPage) {
return;
}
/*
* We switch page at 50% across
*/
CGFloat pageWidth = _scrollView.frame.size.width;
int page = floor((_scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
pageControl.currentPage = page;
}
and then this as well:
- (void)scrollViewDidEndDecelerating:(UIScrollView *)_scrollView {
pageControlIsChangingPage = NO;
}
Not sure what exactly is causing this to happen . . . any ideas? Im stumped :(

Answer 1

I believe the issue was that both the UITableView and the UIScrollView, since they both had the delegates set to self, were calling the same scrollview methods. I added a tag to the main scrollview, and then accounted for it by performing a check on the Tag when adjusting the page, like so
if (_scrollView.tag == 100) {
CGFloat pageWidth = _scrollView.frame.size.width;
int page = floor((_scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
pageControl.currentPage = page;
}
finally

Answer 2

When you scroll the page, does it scrolls correctly?
if (pageControlIsChangingPage)
return;
It seems when you do not change page (i.e. you scroll the tableview instead), return'll not be executed. And so
CGFloat pageWidth = _scrollView.frame.size.width;
int page = floor((_scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
pageControl.currentPage = page;
part will be executed, at this moment, _scrollView.contentOffset.x will less than pageWidth / 2 (even can be 0), as you just scroll up/down, and as a result, the page turn out to be 1.