How to obfuscate an Android library (.jar file) using Proguard in Eclipse

Question

I have seen many posts about how to obfuscate an Android application (.apk file) using ProGuard in Eclipse. Also see http://developer.android.com/guide/developing/tools/proguard.html:

"When you build your application in release mode, either by running ant release or by using the Export Wizard in Eclipse, the build system automatically checks to see if the proguard.config property is set. If it is, ProGuard automatically processes the application's bytecode before packaging everything into an .apk file."

But in case of exporting an Android project in a .jar file using Eclipse Export Wizard, following the described steps (of creating a file proguard.cfg, configuring proguard.config property to proguard.cfg in the file default.properties, using Export Wizard etc.) does not seem to work - I see no obfuscation of class names, etc. in the resulting jar file. I also have the following settings in my proguard.cfg file, but I don't see any output files in my project directory or in the proguard directory (that directory is not even created).

-dump class_files.txt 
-printseeds seeds.txt 
-printusage unused.txt 
-printmapping mapping.txt

I have even created a file project.properties in my project directory with the following line but that did not seem to entice ProGuard into action:

proguard.config=proguard.cfg

There are no activities defined in this project. I am using Android 2.3.1 and Eclipse Galileo 3.5.2 on Windows. Same results with Android 3.0. Seems like the obfuscation step has to be somehow interjected explicitly in the Eclipse Export Wizard. I will appreciate any help or insight. Thanks.

Answer 1

as suggested in the comments to one of the answers above (but which i didn't notice at first because it was buried amongst one of the "additional comments") …

we simply run progruard on the command line (see the first block below) on the library outside of eclipse with the parameters in the second block below in our our proguard.cfg file (and definitely do not use -dontpreverify, or projects that use your project as an android library won't be able to properly be obfuscated due to StackMapTable problems from your project.jar).

command line:

$ java -jar $ANDROID_SDK/tools/proguard/lib/proguard.jar 
  -libraryjars $ANDROID_SDK/platforms/android-18/android.jar @proguard.cfg
  -outjars /tmp/project.jar -verbose

proguard.cfg:

-optimizationpasses 5
-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-dontwarn our.company.project.R*
-injars bin/project.jar
-verbose
-optimizations !code/simplification/arithmetic,!field/*,!class/merging/*

-keep class org.apache.3rdparty.stuff.**
-keep public class our.company.project.ProjectAPI
-keep public class * extends android.app.Activity
-keep public class * extends android.app.Application
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider
-keep public class * extends android.app.backup.BackupAgentHelper
-keep public class * extends android.preference.Preference

-keepclassmembers public class our.company.project.ProjectAPI {
    public static <fields>;
}

-keepclasseswithmembernames class * {
    native <methods>;
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet);
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet, int);
}

-keepclassmembers class * extends android.app.Activity {
    public void *(android.view.View);
}

-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keep class * implements android.os.Parcelable {
    public static final android.os.Parcelable$Creator *;
}

it's possible not all of the parameters and -keep items are strictly necessary (other than not using -dontpreverify as previously mentioned), but most of these make sense to me as items that need to be there if you have an Activity class extension in the library you are exporting.