I am using Eclipse. I am facing this issue Right after GOOGLE IO 2013 when i updated my ADT plugin, Android SDK tools to Revision 22 and Android SDK platform-tools to revision 17
All of my projects that previously worked have started throwing ClassNotFoundException after this update for no reason. I have searched stackoverflow but none of the answers seem to solve my problem.
i have Solved this issue and i thought of sharing it with everyone.
I have noticed that there is a new Android Package named as Android Private Libraries and after hours of trying i found a way to fix this.
Right Click on your Project then
Goto Build Path-> Configure Build Path -> Order and Export
when you are there you should check the Android Private Libraries and then click OK button.
if you still face the problem delete all the files inside your bin folder and rebuilt you project.
Hope this helps others who are facing the same problem as me
Faced the same problem when i updated the adt try this
In Eclipse go to:
"Project" -> "Properties" -> "Java Build Properties"
On the "Order and Export" tab I checked "Android Private Libraries" on my project. I also did this for the library project it references. This fixed my class not found errors following upgrading to SDK 22.
来源：https://stackoverflow.com/questions/16642868/classnotfoundexception-is-thrown-by-all-android-projects-that-used-some-sort-of