Qualifier name rules
Here are some rules about using configuration qualifier names:
- You can specify multiple qualifiers for a single set of resources, separated by dashes. For example, drawable-en-rUS-land applies to US-English devices in landscape orientation.
- The qualifiers must be in the order listed in table 2. For example:
- Wrong: drawable-hdpi-port/
- Correct: drawable-port-hdpi/
- Alternative resource directories cannot be nested. For example, you cannot have res/drawable/drawable-en/.
- Values are case-insensitive. The resource compiler converts directory names to lower case before processing to avoid problems on case-insensitive file systems. Any capitalization in the names is only to benefit readability.
- Only one value for each qualifier type is supported. For example, if you want to use the same drawable files for Spain and France, you cannot have a directory named drawable-rES-rFR/. Instead you need two resource directories, such as drawable-rES/ and drawable-rFR/, which contain the appropriate files. However, you aren't required to actually duplicate the same files in both locations. Instead, you can create an alias to a resource.
After you save alternative resources into directories named with these qualifiers, Android automatically applies the resources in your app based on the current device configuration. Each time a resource is requested, Android checks for alternative resource directories that contain the requested resource file, then finds the best-matching resource(discussed below). If there are no alternative resources that match a particular device configuration, then Android uses the corresponding default resources (the set of resources for a particular resource type that doesn't include a configuration qualifier).
Creating alias resources
When you have a resource that you'd like to use for more than one device configuration (but don't want to provide as a default resource), you don't need to put the same resource in more than one alternative resource directory. Instead, you can (in some cases) create an alternative resource that acts as an alias for a resource saved in your default resource directory.
Note: Not all resources offer a mechanism by which you can create an alias to another resource. In particular, animation, menu, raw, and other unspecified resources in the xml/ directory don't offer this feature.
For
example, imagine you have an app iconicon.webp, and need unique version of it for
different locales. However, two locales, English-Canadian and French-Canadian,
need to use the same version. You might assume that you need to copy the same
image into the resource directory for both English-Canadian and
French-Canadian, but it's not true. Instead, you can save the image that's used
for both as icon_ca.webp (any name other than icon.webp). Then create an icon.xml file in res/drawable-en-rCA/ and res/drawable-fr-rCA/that refers to
the icon_ca.webp resource using the <bitmap> element.
This allows you to store just one version of the PNG file and two small XML
files that point to it. (An example XML file is shown below.)
Drawable
To create an alias to an existing drawable, use the <drawable> element. For example:
If you save this file as drawables.xml (in an alternative resource directory, such as res/values-en-rCA/), it is compiled into a resource that you can reference
as R.drawable.icon, but is actually an alias for the R.drawable.icon_ca resource (which is saved in res/drawable/).