Adding UiImageView to UiScrollView one at a time... but how?

Question

My problem is that my 300 images are being added to UiScrollView and shows up after it's done finishing with addsubview: calls.

How do I set it up so that it adds a subview, who's up on the Screen .. and continue adding ?

Answer 1

You could add to UIScrollView only first couple of pictures that fit the screen and then add others on request, when user scrolls you have to check bounds and add new image if it would be displayed.

I'm not sure about the code details though.

I know for a sure that UIScrollView with 3 images are shown in demo in the lecture 8 (including source code) at Stanford's CS193P course about iPhone development, the presenter (a guy from Apple) mentioned in the video (on iTunesU) that you could load up on demand other images - he just gave general pointers not the actual solution.

But if you need to display screen full of icon size images (kind of like iphone image library) maybe it would be better to try UITableView (I haven't used it for that purpose yet but give it a try).

Answer 2

stefanB's answer is a good one. For the code details, I'd suggest you take a look at - [UIView drawRect:]. Given the size of each of your rows, you can easily calculate when the passed rect represents a new cell being brought into view due to a scroll, and then update with the new image accordingly.

Have you thought about putting your images not in a UIScrollView, but in a UITableView and having that handle all the caching and lazy loading for you? It sounds more specialized to handle what you'd like to do.