How to add external java library to custom Android framework?

Question

Can someone enlighten me on how to include an external java framework to android framework and compile it as a part of the custom android framework?

The idea is to make this external framework a part of my custom android framework and expose it as android service for other processes to use.

In essence what I did is -

1. checked for android port of the java framework
2. Copied the src dir (including all the external jar files) from the ported framework to framework/base/core/java/android/
3. Edited ActivityManager in the framework to call the copied library
4. run make

Is this the right approach to edit Android framework? Since, I am including the java files and associated external jars of the external project inside the Android framework I suspect make fails while converting the jars to dex.

Can somebody point me towards any available resources dealing with Android Framework internals and on how to edit Android framework?

I checked the Tutorial: Android Internals - Building a Custom ROM, Pt. 2 of 2 on youtube from this year's Marko Gargenta presentation in Beijing, China. But he didn't make it (i.e. adding external framework or jars) clear either.

Answer 1

First: I'm not very experienced in the Android build process, so there might be a better solution, but this one should work (at least for Android 2.2).

I assume, that you use Eclipse for the source code modification and already executed a successful make -j4...

• Create a new source folder: external/<your-library>/src
• Copy all Java source files into this folder.
• Open the following make file: <android>/frameworks/base/Android.mk

• Search for # Build ext.jar and add your library as follows:

  [...]
  ext_dirs := \
      ../../external/apache-http/src \
      ../../external/<your-library>/src \
      ../../external/gdata/src \
      ../../external/protobuf/src \
      ../../external/tagsoup/src
  [...]
  

• Now you should be able to access these libraries from the Android framework...
• Finally execute make -j4 ext to build only the external module,
• Or make -j4 to build all changed files (if a previous build exists in /out/).

Answer 2

README.txt from git repo in https://android.googlesource.com/platform/vendor/sample is a good example howto do it. It's good to clone it to see the examples.

Basically you need to create jar file and add it in filesystem, add xml configuration into /system/etc/permissions/ and declare <uses-library> in apk's AndroidManifest.xml.

In my case I had problem with adding <uses-library> on a wrong place (not in <application>).

So it's good to check the result with:

$ aapt dump badging Foo.apk | grep uses-library
uses-library:'android.foo'