Added in API level 1
android
Contains resource classes used by applications included in the platform and defines application permissions for system features.
You can use some resources directly from these R classes in your own
applications, but you should generally use only resources that you've provided directly in your
application, in order to provide a cohesive application package that has no external dependencies.
In particular, you should not use drawable resources from the android package, because they
may change between platform versions, causing unforeseen conflicts with your design. Typically,
styles are the only resources you should use directly from these
resources.
For information about using resources, see the Application Resources developer guide.