Question

I’m using the code from this tutorial to create a UIScrollView which allows scrolling through pages. Put in another way, the user can drag the screen to switch from one UIView to another. The code basically looks like this:

- (void)loadView {
[super loadView];
self.view.backgroundColor = [UIColor redColor];
UIScrollView *scroll = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
scroll.pagingEnabled = YES;
NSInteger numberOfViews = 3;
for (int i = 0; i < numberOfViews; i++) {
CGFloat yOrigin = i * self.view.frame.size.width;
UIView *awesomeView = [[UIView alloc] initWithFrame:CGRectMake(yOrigin, 0, self.view.frame.size.width, self.view.frame.size.height)];
awesomeView.backgroundColor = [UIColor colorWithRed:0.5/i green:0.5 blue:0.5 alpha:1];
[scroll addSubview:awesomeView];
[awesomeView release];
}
scroll.contentSize = CGSizeMake(self.view.frame.size.width * numberOfViews, self.view.frame.size.height);
[self.view addSubview:scroll];
[scroll release];
}

My question is how can I detect which page the user is on? Like logging “1” for page 1, “2” for page 2, etc.

Thanks!

Answer 1

You can get the current page number by using the scroll view’s content offset and its width.

int currentPage = (scrollView.contentOffset.x / scrollView.frame.width) + 1;
NSLog(@"current page: %d", currentPage);

You should take y offset into account if the scrolling is done vertically.