NoClassDefFoundError for code in an Java library on Android

Question

I am experiencing an error quite often among my users. The app crashes during startup. When the MainActivity is supposed to be loaded the VM apparently cannot find the class

Answer 1

If none of the above works (like it happened to me), and you're using as a library another project in Eclipse.

Do so: Right click project -> Properties -> Android -> Library -> Add

That did it for me! Adding a project as a library (Project Properties)