“Conversion to Dalvik format failed with error 1” on external JAR

Question

In my Android application in Eclipse I get the following error.

UNEXPECTED TOP-LEVEL EXCEPTION:
java.lang.IllegalArgumentException: already add

Answer 1

My own and only solution that I found today after four hours of testing all the solutions, is a combination of many solutions provided here:

• Delete project from Eclipse
• Delete files in \bin and \gen from project folder
• Remove references to libraries into .classpath file in root project folder
• Restart Eclipse with command line : eclipse -clean
• Import project
• Right click on project - select Properties > Java Build Path > Libraries and remove everything else than Android XX.Y
• Finally clean project, wait for automatic Building or Build it
• Launch and now it works! At least for me...

I tried every step at a time and many combinations, but only the succession of all steps at once made it! I hope I won't face this again...