7 inch Android tablets will get Honeycomb, thanks to new layout system in 3.2

Since 2009, Android supported three general screen size categories: small, medium, and large. But the introduction of tablet-specific Android Honeycomb in early 2011 brought support for the extra large screen size category and drove a wedge between Android phones and Android tablets.

You see, Honeycomb was created to specifically take advantage of the increased screen real estate of tablets, and the "extra large" screen category was born. But tablets with 7" screens like the original Samsung Galaxy Tab, the Dell Streak 7, and the Archos Home Tablet have awkward screen dimensions which make them fit into the "large" category, but really only when viewed in the landscape orientation. Because of this strange screen quality, 7" tablets didn't even support the version of Android built for tablets.

Today in the Android Developer blog, Dianne Hackborn revealed that Android 3.2, the latest version of Honeycomb, will support tablets with 7" screens. Of course, this is no surprise, since Huawei announced in June that its 7" MediaPad would be running Android 3.2.

Hackborn explained that this is possible because Android 3.2 no longer shoehorns Android into simple screen size "buckets," but instead uses a dynamic layout selection model based on a device's "dp" units. Dp, or "Density Independent Pixels" is an abstract unit of measurement that Android uses instead of dpi and px which is the equivalent to one physical pixel on a 160 dpi screen.

"At runtime, the system transparently handles any scaling of the dp units, as necessary, based on the actual density of the screen in use," Android's developer guide says. "The conversion of dp units to screen pixels is simple: px = dp * (dpi / 160). For example, on a 240 dpi screen, 1 dp equals 1.5 physical pixels. You should always use dp units when defining your application's UI, to ensure proper display of your UI on screens with different densities."

Now, "Smallest width dp" is used instead of the screen size "bucket," and it provides a continuous range of numbers giving the most effective size for the interface.

"This number is based on width because that is fairly universally the driving factor in designing a layout," Hackborn said. "A UI will often scroll vertically, but have fairly hard constraints on the minimum space it needs horizontally; the available width is also the key factor in determining whether to use a phone-style one-pane layout or tablet-style multi-pane layout."