Why isn't my UIPageControl updating when the ScrollView scrolls? - ios

Question

I'm trying to make a table whose cells have UIPageControls with ScrollViews in them. The ScrollViews work and the PageControls are there, but the PageControl does not update when scrolling happens except for on the bottom cell. Here is my code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath: (NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell"];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
cell.contentView.backgroundColor = [UIColor blueColor];
UIColor *color = [colorsArray objectAtIndex:indexPath.row];
scrollView = [[UIScrollView alloc] init];
[scrollView setDelegate:self];
CGRect screen = [[UIScreen mainScreen] bounds];
CGFloat width = CGRectGetWidth(screen);
CGFloat height = tableView.rowHeight;
scrollView.frame = CGRectMake(0, 0, width, height/1.25);
scrollView.contentSize=CGSizeMake(width*3,height/1.25);
scrollView.pagingEnabled = YES;
[scrollView setBackgroundColor:color];
[scrollView setShowsHorizontalScrollIndicator:NO];
scrollView.clipsToBounds = YES;
NSUInteger i;
int xCoord=width/25;
int yCoord=width/25;
int buttonWidth=width/8;
int buttonHeight=width/8;
int buffer = width;
for (i = 1; i <= 4; i++)
{
UIButton *aButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
aButton.backgroundColor = [UIColor blackColor];
aButton.frame = CGRectMake(xCoord, yCoord,buttonWidth,buttonHeight );
[aButton addTarget:self action:#selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
aButton.tag = i;
UIImage *buttonImage = [picsArray objectAtIndex:indexPath.row];
[aButton setBackgroundImage:buttonImage forState:UIControlStateNormal];
[scrollView addSubview:aButton];
xCoord += buttonHeight + buffer;
}
[cell addSubview:scrollView];
pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(0, height/1.25, width, height/4)];
pageControl.numberOfPages = 3;
pageControl.currentPage = 0;
pageControl.userInteractionEnabled =YES;
[pageControl addTarget:self action:#selector(pageAction:) forControlEvents:UIControlEventValueChanged];
[cell addSubview:pageControl];
return cell;
}
- (void)scrollViewDidScroll:(UIScrollView *)sender {
// Update the page when more than 50% of the previous/next page is visible
CGFloat pageWidth = scrollView.frame.size.width;
int page = floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
pageControl.currentPage = page;
}
- (void)pageAction:(UIPageControl *)sender {
// update the scroll view to the appropriate page
CGRect frame;
frame.origin.x = scrollView.frame.size.width * pageControl.currentPage;
frame.origin.y = 0;
frame.size = scrollView.frame.size;
[ scrollView scrollRectToVisible:frame animated:YES];
}

Answer 1

That is because you have reference only to scroll view and page control generated for the last cell:
// this references are redefined every time new cell is generated
scrollView = [[UIScrollView alloc] init];
pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(0, height/1.25, width, height/4)];
You could try to use sender in your UIScrollView delegate method:
- (void)scrollViewDidScroll:(UIScrollView *)sender {
// Update the page when more than 50% of the previous/next page is visible
CGFloat pageWidth = sender.frame.size.width;
int page = floor((sender.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
// !!! but here is another problem. You should find reference to appropriate pageControl
pageControl.currentPage = page;
}
But there will be one more problem: you should get reference to the appropriate UIPageControl object. You could use tags, array or anything else for that purpose.