Infinite List
From MobileDesign
Gmail Java app, for both inboxes and message display, will fetch more in the list when you scroll down far enough. It also removes from cache items "far away" from current focus, thus maintaining good memory management.
Twitterific has to display a news stream, with items being added to top of list. When the app is launched, the news stream is displayed, with focus on the same entry as before. Pictures and new items are loaded, but reading can happen immediately. There is also an option for a "More' link in order to view previous posts. An ad, with image right-aligned, is placed at the top of the old items and below the new ones.
[edit] Scrolling Recommendations
- Limit markup size to what the device can comfortably handle
This sounds obvious, but the “comfortably” bit is important, too. We’ve seen web sites that would render on a Motorola RAZR, but were so heavy that the device didn’t have any capacity to spare for moving the cursor in a timely fashion.
- Ensure users have a reason to scroll
Make the top part of your page/screen compelling. Avoid closure, false bottoms. Create expectations that more is below by adding a link to click on. This is especially important on landing pages.
- Use just-in-time fetching for infinite lists
For applications and browsers that support Javascript, don’t fetch a new page at all; instead add items at the bottom of the list as the user nears it. You can remove items at the top if you run out of memory. The Gmail Java ME application does this very well.
- Provide accelerators for certain lists
Opera Mini uses left and right to page-scroll up and down in some modes. Openwave browsers support volume up and down for page scrolling. The iPhone Address Book provides letter shortcuts and handles the problem of the letter being too small by only using it to scroll to a spot, rather than filter. Some sites have within-page navigation.
- Reduce page length by
Using only key navigation links (maybe just Home) rather than a full set on every page. Providing the first few items of a topic area, like the first 5 comments, and linking to a full list of comments Only putting the spacing needed for touch users on touch devices
