This is the closest that you can get:
Step #1: Create a regular Android library project, and get it working.
Step #2: Copy that Android library project into another directory.
Step #3: Create a JAR from the compiled Java classes from the original Android library project, and put that JAR in the libs/
directory of the copy you made in Step #2. You should be able to run ProGuard on this JAR manually, though I haven't tried that.
Step #4: Remove everything inside the src/
directory of the copied library project, leaving behind and empty src/
directory.
Step #5: ZIP up or otherwise distribute the copied Android library project.
This will give you an Android library project like the Play Services one, where the resources are available, but the source code is not.
UPDATE: An even better approach nowadays is to package your library project as an AAR, which is Android's native way of creating a reusable artifact from your compiled code plus required resources. At the present time (July 2014), Gradle for Android, Android Studio, and the android-maven-plugin
can create and consume AARs.
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