Question

So I have a UIScrollview that scrolls horizontally with paging through a bunch of different UIImageViews containing user avatars. But, I want to only load the avatars from their URL IFF they are actually showing on the screen (4 are showing at a time, but I can scroll through like 30 or more or less). Is there a way of detecting which UIImageView/ which page it is on? Or does anyone have any general recommendations or ideas for how I should go about this problem? Thank you in advance.

Answer 1

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
        CPoint offset = scrollView.contentOffset;
        int index = offset.x / pageWidth;
        switch (index) {
            case 0:
                //first ImageView
                break;
            case 1:
                //second ImageView
                break;
            default:
                break;
        }
    }

Or If you tag your imageViews (starting at 1) you can retrieve them via:

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
    CPoint offset = scrollView.contentOffset;
    int index = offset.x / pageWidth;
    UIImageView *visibileImageView = (id)[scrollView viewWithTag:index+1];
}

You can use scrollViewDidScroll to detect the position at any point if you use the modulus:

int index = (offset.x - offset.x % pageWidth)/pageWidth;