How smart is Eclipse / ADT when it comes to Android Library Projects?

Question

So, I've got a handful of "Utility" style classes in some of my projects. I'm curious if I can move them to an Android Library Project that contains all or most of my non-app specific glue code (wrappers and interfaces, mostly).

So, my question is what happens to the files I don't need in that library. I know Android Library Projects basically just copy their code into the other project, so if I say use 25% of the code in my "general purpose" library, will my app actually contain the bytecode for all 100%, or does it properly strip it down to only the stuff I need.

I had some issues with unused classes in Proguard in the past, so I'm just once-bitten, twice shy with the ADT now...

Answer 1

Unfortunately, all your projects will grow when the library is getting bigger - even if most contents of that library are not used. I tested it myself by creating an app A and a library L. If L is a library used in A, the classes.dex file (and therefore the A.apk file) is growing if I add more classes - even if they are not used.

To sum up: Right now I would create a basic library for certain things that are small and that may be used by many projects, and create a new library for every new component that is going to be larger and only is used by some projects. A good candidate for a new library would be a new UI component with multiple images defined in the resources. A good candidate for the base library are commonly-used methods and things like file caches, for example. Compiled code is compressed quite heavily for Dalvik, which you can see here. (The whole presentation is actually fun to watch :-)

Edit: If ProGuard is activated, it will also remove unused code for you. The default proguard.cfg is sufficient. It will not run on the (default) debug built, but when the final .apk is compiled. So it actually is possible!

Answer 2

I have used 3 level deep Android library projects successfully though it is kind of a pain. The primary use-case is when there are a set of resources and classes that you want to share across a few projects. Since I use a version control system, I would rather not use symlinks.