I’ve read the official guide about different densities and resolutions, but cannot find how to use different assets for the screens with the same density? For example, 320×480 and 480×800 use the same mdpi, but obviously it would be better not to scale graphics programatically and use pre-scaled assets. Is it possible to force application use different graphics for different resolutions with the same dpi?
Android version 2.2+, normal and large screens
The section of the Developers Guide you should see is Supporting Multiple Screens.
If you want to use different drawables for different-sized screens at the same dpi, then implement layouts and drawables in different size and/or display-width buckets.
The Guide tells you in what order to name the resource-path qualifiers. Or, you can let the XML file creation wizard in Eclipse do it for you.