How can I solve this? I had tried many things in here, and nothing seems to work for me. I had tried importing and cleaning, buildings and restarting eclipse, and nothing seems to work.
I finally found the solution.
This error happens when I added a library that is the same I am using in my project, so, I need to exclude the library from my main project and let just the one that comes with the library I imported to my main project.
So, 1. Go to bould path -> Order and Export 2. Uncheck the jar that is the same that the imported library uses. Click ok.
Now, you are ready to continue developing!