Also, you should clear the displayed content and show "Retrieving" on the screen before attempting to download the next set of content, otherwise, the existing content will show on the screen while you are retrieving the new content and that is confusing to the user.
Another suggestion is to keep the content you downloaded in an array, so that you don't have to hit your server every time the user browses to another category on the filter banner, this will improve the user experience for your channel. Typically, you would have a flag set for each category in the banner so that you could track whether the content has been downloaded already, so you don't do it twice.
- Joel