Once you use the dex2jar tool, see above note, you can go ahead and use JD-GUI 

JD-GUI is a tool that will help decompile some code that is very similar to the original source code.

The sequence would be 

./dj2-dex2jar.sh <apkname.apk> -o <output-file.jar>

Then

Run JD-Gui - SELECT the File Menu and select the <output-file.jar> as seen above

This will show a hierarchial view of the contents on the left hand side.