Android Project Structure

Every Android Project has a specific directory structure. The Android build tools do a few extra things to prepare the actual application that will run on the device or emulator.

Basic Structure

When you create a new Android project ( via Command Line android create project), you gets the following in the project's root directory:

• AndroidManifest.xml: An XML file that describes the application being built and what components (activities, services, etc) are being supported by the application.
• ant.properties:  customizable properties for the build system. You can edit this file to override default build settings used by Ant.
• assets/: Directory holds other static files that you want packaged with application for deployment on tho the device.
• bin/: The directory that holds the application once it is compiled.
• build.xml: Used as part of the Apache Ant based command line build process.
• gen/: Directory in which Android's build tools place source code that they generate.
• jni/:  Contains native code sources developed using the Android NDK.
• libs/: Directory holds any third-party JARs your application requires.
• progurd.cfg: Used for integration with ProGuard to obfuscate your Android Code.
• res/: Directory holds resources ( icon, GUI layout etc).
• src/: Directory holds the Source Code.

Details of bin/ directory

• bin/classes/: Holds the compiled Java Classes
• bin/classes.dex: Holds the executable created from those compiled Java Classes.
• bin/yourapp.ap_: Holds your application resources, packaged as a ZIP file.
• bin/yourapp-*.apk: The actual Android Application (where * varies).

 Details of res/ directory

• res/drawable/: For images 
• res/layout/: For XML-based UI layout specifications
• res/menu/: For XML-based menu specifications
• res/raw/: For general purpose files 
• res/values/: For strings, dimensions, etc
• res/xml/: For other general purpose XML files