I included a jar file in my Android project as explained in How can I use external JARs in an Android project?. With both methods described by MannyNS and Vinayak B. in this
I think that the problem is that you try to add jar that contains Android code. You cannot do this. To include Android code you should create Android library. Simply create an Android project and in the project-properties Android section set that this is library project. After that you'll be able to add this library to your projects. For more about Android libraries you can read here.
Update: I've tried your code now. It works in my case. The only difference that I've made is during export of Jar I've checked Export Java source files and resources. Hope this will help you. Try it!