Question

I am trying to add a page control to my scroll view, and have followed numerous web tutorials, the majority which use the same code as this tutorial. However, once I place the code into my project, even with me making changes to the code to try to make it work, it just doesn’t. I have managed to make the code work for when the page control is pressed, however it just won’t work for the page scrolling. My issue is similar to this, although the answers are of no help. Here is my code:

MainViewController.h

@interface MainViewController : UIViewController
{
UIScrollView *svCollegeMain;
UIScrollView *svCollegePage;
UIPageControl *pcCollege;
UIView *viewP1;
}

@property (nonatomic, retain) IBOutlet UIScrollView* svCollegeMain;
@property (nonatomic, retain) IBOutlet UIScrollView* svCollegePage;
@property (nonatomic, retain) IBOutlet UIPageControl * pcCollege;
- (IBAction)changePage;

@end

and MainViewController.m

@implementation MainViewController

@synthesize svCollegeMain, svCollegePage, pcCollege;

- (void)viewDidLoad 
{
[super viewDidLoad];
self.svCollegeMain.contentSize = CGSizeMake(960, 332);
self.svCollegePage.contentSize = CGSizeMake(320, 500);
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
    // Custom initialization
}
return self;
}

- (void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];

// Release any cached data, images, etc that aren't in use.
}

- (void)scrollViewDidScroll:(UIScrollView *)sender
{
CGFloat pageWidth = 320;
int page = floor((svCollegeMain.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
pcCollege.currentPage = page;
}

- (IBAction)changePage 
{
CGRect frame;
frame.origin.x = self.svCollegeMain.frame.size.width * self.pcCollege.currentPage;
frame.origin.y = 0;
frame.size = self.svCollegeMain.frame.size;
[self.svCollegeMain scrollRectToVisible:frame animated:YES];
}

#pragma mark - View lifecycle

- (void)viewDidUnload
{
[super viewDidUnload];
self.svCollegeMain = nil;
self.svCollegePage = nil;
self.pcCollege = nil;
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

Just incase this makes any difference, my view is set out with a view, then a main scroll view and page control within this view, another view and scroll view (next to each other) within the main scroll view, and finally a final view in the second scroll view (all in IB, did not want too much code), and everything is linked up in IB.

Answer 1

I notice that your MainViewController doesn’t declare itself as implementing UIScrollViewDelegate, so I also assume that you’ve forgotten to set it up as the delegate for the scroll view in IB (otherwise it wouldn’t compile).

Since it has no delegate defined, the scroll view won’t be calling your scrollViewDidScroll function.

Tim