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.
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
Even though there are three separate layout files here, they all generate only one layout ID in R.java.
This ID looks as follows:
When you retrieve the layout corresponding to this layout ID, you get the appropriate layout suitable for that device layout.
The directory extensions
-land are called configuration
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.
Most of the available configuration qualifiers are listed as follows. New qualifiers may be added with newer APIs.
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
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.