UIScrollView with page control - iphone

Question

Have three different page view controllers using as views in uiscrollview. UIScrollView with pagecontrol is displaying only third page as current page but not displaying two other pages. Pagecontrol is also not visible.
- (void)viewDidLoad
{
[super viewDidLoad];
PageOne *pageOne = [[PageOne alloc] init];
pageOne.view.frame = CGRectMake(0, 0, 320, 420);
PageTwo *pageTwo = [[PageTwo alloc]init];
pageTwo.view.frame = CGRectMake(0, 0, 320, 420);
PageThree *pageThree = [[PageThree alloc] init];
pageThree.view.frame = CGRectMake(0, 0, 320, 420);
scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
[scrollView setContentSize:CGSizeMake(self.view.frame.size.width * 3, self.view.frame.size.height)];
[scrollView setDelegate:self];
[scrollView setPagingEnabled:YES];
[scrollView setShowsHorizontalScrollIndicator:YES];
[scrollView addSubview:pageOne.view];
[scrollView addSubview:pageTwo.view];
[scrollView addSubview:pageThree.view];
[self.view addSubview:scrollView];
_pageControl = [[UIPageControl alloc] init];
[_pageControl setCurrentPage:0];
[_pageControl setNumberOfPages:3];
[_pageControl sizeToFit];
[_pageControl setFrame:CGRectMake((scrollView.frame.size.width / 2) - (_pageControl.frame.size.width / 2), scrollView.frame.size.height - _pageControl.frame.size.height, _pageControl.frame.size.width, _pageControl.frame.size.height)];
[self.view addSubview:self.pageControl];
[super viewDidLoad];
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
_pageControl.currentPage = lround(scrollView.contentOffset.x / scrollView.frame.size.width);
}
Right now it is displaying only pageThree. Why not displaying pageOne and pageTwo.
Why not displaying PageOne, pageTwo and then pageThree in series.
Thanks for help.

Answer 1

You are dividing your contentOffset by the full width of the scroll view instead of the width of each page (which I would have thought would result in page1 always showing not page3). The result is that the offset for page2 is 320, the width of the scrollView is 960, and 320/960 is 0.333
Also, because you have paging enabled you should implement
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
And set the currentPage of the pageControl there, that way you will only be calling it exactly at the edges of each page and not every point in between(no need for rounding).
try commenting out your scrollViewDidScroll method and instead use
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
[pageControl setCurrentPage:scrollView.contentOffset.x/320];
}
this has always worked for me in the past.

Answer 2

My first answer addressed the wrong thing...You can only see page 3 because all three pages are added on top of each other. Try:
page1 CGRectMake(0,0,320,420)
page2 CGRectMake(320,0,320,420)
page3 CGRectMake(640,0,320,420)
then they will be in the scroll view next to each other instead of on top of each other.