I find the solution to decompile a file dex to jar from this link http://code.google.com/p/dex2jar/downloads/list but i don\'t understand how to use it.
If anyone is still looking for an easy way to decompile an APK (with resource decompiling), have a look at the tools I have created: https://github.com/dirkvranckaert/AndroidDecompiler
Just checkout the project locally and run the script as documented and you'll get all the resources and sources decompiled.