Loading dynamical images to UIScrollVIew - iphone

Question

what I would like to do is to build a UIScrollView which contains a lots of images, the problem is that I don't want to load all the images to the scroll view at once for performance issues, so if someone can suggest and help me to build a UIScrollView which can add images on runtime, for example when I scroll left I get image and the next image is allocated when needed, paging on.

Answer 1

Use this delegate method for add new image.
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate;
// called on finger up if user dragged. decelerate is true if it will continue moving afterwards

Answer 2

You can implement UIScrollViewDelegate and use its methods like
- (void)scrollViewDidScroll:(UIScrollView *)scrollView;
which tells you about any offset changes in the Scroll View, and then you can load whichever image should appear at that offset at run-time. For that, you would have to keep track of the current offset and the page of your scroll view.

Answer 3

Look into the Apple's PageControl Sample Code
This could be a good starting point

Answer 4

- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
float currPos = scroll.contentOffset.x;
BOOL movingRight = ( currPos / scroll.frame.size.width ) > 1 ? YES : NO ;
if (movingRight) {
NSLog(#"RIGHT");
[photo2 setImage:[UIImage imageNamed:#"22.jpg"]];
photo2.frame = CGRectMake(scroll.frame.size.width * 2, 0, scroll.frame.size.width, scroll.frame.size.height);
}else{
NSLog(#"LEFT");
[photo2 setImage:[UIImage imageNamed:#"33.jpg"]];
photo2.frame = CGRectMake(0, 0, scroll.frame.size.width, scroll.frame.size.height);
}
//NSLog(#"%f",currPos);
}
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
UIImage *img = [photo1 getImage];
[photo1 setImage:[photo2 getImage]];
[self.scroll scrollRectToVisible:CGRectMake(self.scroll.frame.size.width, 0, self.scroll.frame.size.width, self.scroll.frame.size.height) animated:NO];
[photo2 setImage:img];
}