Question

Basically, I want to have an app with only one view that has an image on it. I want to be able to swipe left or right and have the first image go out of the view and the second image to come in. The images are the same and I want it to look like they are connected (like scrolling down a rope where the pattern just repeats, but it looks like a constant scroll). I need it to be able to change the image or restart after a series of swipes. I know that I need to turn pagination ON in the UIScrollView, but I am new to iOS and am having trouble.

Ultimately, I want to have the iPhone vibrate every so-and-so swipes (and restart the pattern).

I’m sure that there are a lot of ways to do this (i.e. a TableView) so feel free to just point me in the direction of some references if the answer is tedious to explain.

Thanks!

FOLLOW UP:

I found an Apple example that did very nearly what I wanted to do. I made a lot of adjustments to it, but I’m banging my head against a wall trying to get the images to cycle. Here is what I think is the offending code, but I’m not sure what the solution is, as the ScrollView is functional, it just doesn’t reset the center to the current view. Any ideas?

    - (void)layoutScrollImages
{
        UIImageView *view = nil;
        NSArray *subviews = [scrollView1 subviews];

    // reposition all image subviews in a horizontal serial fashion
    CGFloat curXLoc = 0;
    for (view in subviews)
    {
        if ([view isKindOfClass:[UIImageView class]] && view.tag > 0)
        {
            CGRect frame = view.frame;
            frame.origin = CGPointMake(curXLoc, 0);
            view.frame = frame;

            curXLoc += (kScrollObjWidth);
        }
    }

    // set the content size so it can be scrollable
    [scrollView1 setContentSize:CGSizeMake((kNumImages * kScrollObjWidth), [scrollView1 bounds].size.height)];

}

Answer 1

I’d just use a UIScrollView. Set the contentWidth to be 3 times the width/height of the view (for 3 pages) and set the contentOffset to be the center ‘page’ (view.bounds.size.width or view.bounds.size.height depending on whether you’re scrolling horizontally/vertically respectively) . You’ll need to setup a delegate for the UIScrollView (probably the view controller) and implement - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView. This will be called when the scroll view has finished decelerating. Once it has finished decelerating, reset the contentOffset back to the center view. This should give the impression of an infinite scroll. You can also set a counter to increment in the scrollViewDidEndDecelerating method to increment the counter or initiate the vibration.

You shouldn’t need to keep repositioning the images. Just set the images once in the scrollView:

//Horizontal arrangement
UIImage *image = [UIImage imageNamed:@"nameOfImage.png"];
UIImageView *imageView1 = [[UIImageView alloc] initWithImage:image];
UIImageView *imageView2 = [[UIImageView alloc] initWithImage:image];
UIImageView *imageView3 = [[UIImageView alloc] initWithImage:image];
NSArray *imageViews = [NSArray arrayWithObjects:imageView1, imageView2, imageView3];
UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
[self.view addSubview: scrollView]; //This code assumes it's in a UIViewController
CGRect cRect = scrollView.bounds;
UIImageView *cView;
for (int i = 0; i < imageViews.count; i++){
    cView = [imageViews objectAtIndex:i];
    cView.frame = cRect;
    [scrollView addSubview:cView];
    cRect.origin.x += cRect.size.width;
}
scrollView.contentSize = CGSizeMake(cRect.origin.x, scrollView.bounds.size.height);
scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0); //should be the center page in a 3 page setup

So the images are setup, you don’t need to mess with them anymore. Just reset the contentOffset when the scroll views stops (note: you need to make sure you’re the delegate of the scroll view or you’ll not receive the message when the scroll view stops):

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
    scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0);
}

Please forgive any typos. I wrote it out by hand.