error in libs folder - android

Question

I was working on my app, editing and coding some xml and layouts when suddenly I got an error on my libs folder. It's very weird because I haven't actually modified or changed any base classes or something. Moreover, I just noticed I lost also my R.java file and all of the references are gone.

What possibly can be the problem? I tried to clean+build the project but it didn't work. Here is a screenshot of my eclipse: http://i.gyazo.com/959040321d1fd6d00ee0b9a90133aa9c.png

Answer 1

Place the jar in the root folder of your project. Then you can add it to your classpath . (you cannot place a jar and access it using android.R) You can add the jars to your build path by right clicking on your project->properties and going to Build Path. Then you can add an external jar