Hacking android app (Basic)

Search and download the apk file, you can use following links to search your apk if you don't have one

http://www.androiddownloadz.com/
http://www.freeandroidware.com/
http://www.freewarelovers.com/android

convert extension of the file from .apk to .zip and extract this zip, now you get the resources and other files, to get the classes decompile the file classes.dex to jar with an app from this link http://code.google.com/p/dex2jar/downloads/list

Step 1 extract the contents of dex2jar.*.*.zip file
Step 2 copy your .dex file to the extracted directory
Step 3 execute dex2jar.bat <.dex filename> on windows, or ./dex2jar.sh <.dex filename> on linux

then you can use jd-gui, the source code is quite readable as dex2jar makes some optimizations.

Frequently used Android Intents

Useful and commonly used Android Intents for frequently used tasks like managing apps, making call, sending SMS, eMail etc