Install JDK7
// For Ubuntu sudo apt-get install openjdk-7-jre
Download dex2jar from https://sourceforge.net/projects/dex2jar/files/
Extract dex2jar-version.zip to a folder. for example /home/panxiaobo/, _C:_
// For Linux unzip -x dex2jar-version.zip -d /home/panxiaobo
use dex2jar to generate .jar file. dex2jar will generate a file named someApk-dex2jar.jar in the working folder.
// For Linux, Mac OSX, Cygwin sh /home/panxiaobo/dex2jar-version/d2j-dex2jar.sh /home/panxiaobo/someApk.apk // For Windows C:\dex2jar-version\d2j-dex2jar.bat someApk.apk
use a decompiler to view the source.
that's it