Handling Multiple ScreenSizes
For the first year or so since Android 1.0 was released, all production Android devices had the same screen resolution (HVGA, 320 by 480) and size (around 3.5 inches, or 9 centimeters). Starting in the fall of 2009, though, devices have been arriving with widely disparate screen sizes and resolutions, from tiny QVGA (240 by 320) screens to much larger WVGA (480 by 800) screens.
Of course, users will be expecting your application to be functional on all of these screens, and perhaps take advantage of larger screen sizes to add greater value. To that end, Android 1.6 added new capabilities to help better support these different screen sizes and resolutions.
The Android documentation has extensive coverage ...