Android Tutorial - Android Resources and Configuration








Android resources generalize configuration idea to any configuration of the device. Language is one configuration choice.

Android allows you to pick different sets of layouts based on layout mode for the same resource ID.

Android does this by using different directories for each configuration.

Example

When using the smart phone we can use it vertically or horizontally. The vertical mode is called the portrait mode and the horizontal mode the landscape mode.

The following three main_layout.xml files are all for layout. Android will load the corresponding files. 

\res\layout\main_layout.xml
\res\layout-port\main_layout.xml
\res\layout-land\main_layout.xml




Note

Even though there are three separate layout files here, they all generate only one layout ID in R.java.

This ID looks as follows: 

R.layout.main_layout

When you retrieve the layout corresponding to this layout ID, you get the appropriate layout suitable for that device layout.

The directory extensions -port and -land are called configuration qualifiers.

These qualifiers are case insensitive and separated from the resource directory name with a hyphen (-).

Resources in these configuration qualifier directories are called alternate resources.

The resources in resource directories without the configuration qualifiers are called default resources.

Resource configuration qualifiers

Most of the available configuration qualifiers are listed as follows. New qualifiers may be added with newer APIs.

  • car, desk: Type of docking.
  • en-rUS: Language and region.
  • keysexposed, keyssoft, keyshidden: Kind of keyboard.
  • ldpi, mdpi, hdpi, xhdpi, nodpi, tvdpi: Screen density.
  • long, notlong: Screen type.
  • mccAAA: AAA is the mobile country code.
  • mncAAA: AAA is the carrier/network code.
  • navexposed, navhidden: Navigation keys hidden or exposed.
  • night, notnight: Night or day.
  • nokeys, qwerty, 12key: Number of keys.
  • nonav, dpad, trackball, wheel: Type of navigation device.
  • notouch, stylus, finger: Kind of screen.
  • port, land: Portrait or landscape.
  • small, normal, large, xlarge: Screen size.
  • sw<N>dp, w<N>dp, h<N>dp: Smallest width, available width, available height.
  • v3, v4, v7: API level.

With qualifiers, you can have resource directories shown in the following code. 

\res\layout-mcc312-mnc222-en-rUS
\res\layout-ldpi
\res\layout-hdpi
\res\layout-car




Qualifiers precedence order

Consider the directories as follows. 

\res\layout\main_layout.xml
\res\layout-port\main_layout.xml
\res\layout-en\main_layout.xml

The layout file main_layout.xml is available in two additional variations: for the language or for the layout mode.

Even in portrait mode, Android picks the layout from the layout-en directory, because the language variation comes before the orientation variation.

Please note that string resources are based on individual IDs, whereas layout resources are file-based.