Android Project Folder Structure

Android Tutorials - Herong's Tutorial Examples

∟Android Project Folder Structure

This section describes the Android project folder structure, which has a source folder, a resource folder, a generated-code folder, and a binary folder.

In this tutorial, let's look at the Android application project folder structure using the HelloAndroid application as an example. If you have not created the project yet, run the following command now:

C:\herong>\local\android-sdk-windows\tools\android create project \
   -k com.herongyang -a HelloAndroid -t 2 -p .\HelloAndroid

Now open the project folder \herong\HelloAndroid using the "dir /s \herong\HelloAndroid" command. You will see the following folder structure:

C:\herong\HelloAndroid
   AndroidManifest.xml
   ant.properties
   bin - Binary folder to hold build output
      build.prop
      classes - Binary class files
         com
            herongyang
               BuildConfig.class
               HelloAndroid.class
               R$attr.class
               R$drawable.class
               R$layout.class - Layout resource file
               R$string.class
               R.class
      classes.dex
      classes.dex.d
      HelloAndroid-debug-unaligned.apk
      HelloAndroid-debug-unaligned.apk.d
      HelloAndroid-debug.apk
      HelloAndroid.ap_
      HelloAndroid.ap_.d
      jarlist.cache
      res
         drawable-hdpi - High resolution icon
             ic_launcher.png
         drawable-ldpi - Low resolution icon
            ic_launcher.png
         drawable-mdpi - Medium resolution icon
            ic_launcher.png
   build.xml
   gen
      com
         herongyang
            BuildConfig.java
            R.java
   libs - Empty folder
   local.properties
   proguard-project.txt
   project.properties
   res
      drawable-hdpi - High resolution icon
          ic_launcher.png
      drawable-ldpi - Low resolution icon
         ic_launcher.png
      drawable-mdpi - Medium resolution icon
         ic_launcher.png
      layout - Layout resource files
         main.xml
      values
         strings.xml - String resource file
   src
      com
         herongyang
            HelloAndroid.java

Some detailed explanations of key folders and files in an Android project folder structure based on the Android document:

.\src\ - The source folder which contains your stub Activity file, which is stored at src/your/package/namespace/ActivityName.java. All other source code files (such as .java or .aidl files) go here as well.
.\bin\ - The binary folder which contains output files of the build process. This is where you can find the final .apk file and other compiled resources.
.\jni\ - The JNI (Java Native Interface) folder which contains native code sources developed using the Android NDK (Native Development Kit). You will not have this folder, if you don't have any native code.
.\gen\ - The generated-code folder which contains Java source files generated by ADT (Android Developer Tools), such as your R.java file and interfaces created from AIDL files.
.\assets\ - The asset folder which constrain raw asset files. Files that you save here are compiled into an .apk file as-is, and the original filename is preserved. You can navigate this directory in the same way as a typical file system using URIs and read files as a stream of bytes using the the AssetManager. For example, this is a good location for textures and game data.
.\res\ - The resource folder which contains application resources, such as drawable files, layout files, and string values.
.\res\anim\ - The animation resource folder which contains resource XML files that are compiled into animation objects.
.\res\color\ - The color resource folder which contains resource XML files that describe colors.
.\res\drawable\ - The drawable resource folder which contains bitmap files (PNG, JPEG, or GIF), 9-Patch image files, and XML files that describe Drawable shapes or a Drawable objects that contain multiple states (normal, pressed, or focused).
.\res\layout\ - The layout resource folder which contains XML files that are compiled into screen layouts (or part of a screen).
.\res\menu\ - The menu resource folder which contains XML files that define application menus.
.\res\raw\ - The raw resource folder which contains arbitrary raw asset files. Saving asset files here instead of in the assets/ directory only differs in the way that you access them. These files are processed by aapt and must be referenced from the application using a resource identifier in the R class. For example, this is a good place for media, such as MP3 or Ogg files.
.\res\values\ - The value resource folder that contains XML files that are compiled into many kinds of resource. Unlike other resources in the res/ directory, resources written to XML files in this folder are not referenced by the file name. Instead, the XML element type controls how the resources is defined within them are placed into the R class.
.\res\xml\ - The XML resource folder which contains miscellaneous XML files that configure application components. For example, an XML file that defines a PreferenceScreen, AppWidgetProviderInfo, or Searchability Metadata.
.\libs\ - The library folder which contains private external libraries.
.\AndroidManifest.xml - The project manifest file that describes the nature of the application and each of its components. For instance, it describes: certain qualities about the activities, services, intent receivers, and content providers; what permissions are requested; what external libraries are needed; what device features are required, what API Levels are supported or required; and others.
.\project.properties - The project properties files which contains project settings, such as the build target. This file is integral to the project, so maintain it in a source revision control system. To edit project properties in Eclipse, right-click the project folder and select Properties.
.\local.properties - The local properties file which contains customizable computer-specific properties for the build system. If you use Ant to build the project, this contains the path to the SDK installation. Because the content of the file is specific to the local installation of the SDK, the local.properties should not be maintained in a source revision control system. If you use Eclipse, this file is not used.
.\ant.properties - The Ant properties file which contains customizable properties for the build system. You can edit this file to override default build settings used by Ant and also provide the location of your keystore and key alias so that the build tools can sign your application when building in release mode. This file is integral to the project, so maintain it in a source revision control system. If you use Eclipse, this file is not used.
.\build.xml - The Ant build file for your project. This is only applicable for projects that you build with Ant.