If you want to create DPS folios for Android devices, you should understand a few things about the platform before making design decisions. It’s important to consider the different device sizes and dimensions and how DPS folios are displayed on these devices. I would usually provide a quick summary of what you should consider, but in this particular case, I think it’s better to ask you to sit down, grab a juice box, and spend 10 minutes trying to understand the intricacies of working with DPS on Android. No shortcuts.
Note: If you’re creating a Single Edition app, ignore this article. See this one instead.
(This article was written in October 2012. As the Android platform evolves, I’ll try to update this article.)
Update: New Scaling Up Feature in v28
With the v28 release, the Android viewers now scale up the selected rendition when the folio is smaller than the device dimensions. That’s a game changer that can dramatically simplify your approach to creating folios for the numerous different Android devices. For example, if you create a single folio, such as 1024×768 or 1280×800, the viewer will scale that folio up or down on any device on the market. The Android viewer scales up folios as long as they’re no more than three times smaller than the device’s dimensions.
If you’re using renditions, note that this new scale-up logic doesn’t affect the way renditions are picked. The viewer continues to select the smaller rendition instead of the larger rendition if the larger rendition requires scaling—even a minimal amount of scaling.
[When I get a chance, I'll change my guidance below to account for the new v28 scaling feature. I need to do some testing first...]
Differences Between Android and iOS Devices
You should be aware of a few key differences between how folios are displayed on iOS and Android.
In iOS viewers, content is scaled up to fit in the screen. For example, a 1024×768 folio is scaled up to fit in the 2048×1536 iPad HD screen. However, on Android, viewers never scale up the content. A 1024×600 folio is displayed on a 1280×800 device with big black bars on all sides. Furthermore, on iPad viewers, only folios with a 4:3 aspect ratio will appear. On Android, any folio of practically any size will appear.
In this example, a 1024×600 folio is displayed on a 1280×800 Nexus. Instead of scaling up the content, the viewer adds black bars. (Click to enlarge.)
Although viewers can scale down content on Android devices, it’s a good idea to avoid it for performance reasons.