Android File Structure

This post will take a look at the Android file structure. We will figure out what goes where, and how to make the best of keeping track of all our files.


Android Studio uses Gradle build scripts. Gradle build scripts are a project automation tool wrtten as a DSL. This is where we define our target and minimal SDK. We also use this file to define the versionName and versionCode of our app.

We actually have two build.gradle scripts, a top-level build file and build files for each module. It is also where we identify the minimal and taret SDK for our app.

This file is where we have our dependancy declarations. If we want to add an external library such as UniversalImageLoader, we make it avaialbe by adding:

dependencies {
compile ''
compile 'com.nostral13.univeralimageloader:universal-image-loader:1.9.3'


Files under the /generated directory are auto generated files.


The file is our resources file. It contains all the resource IDs for all the resources in our res/ directory.

public static final class string {
    public static final int abc_action_bar_home_description=0x7f060000;
    public static final int abc_action_bar_home_description_format=0x7f060001;
    public static final int abc_action_bar_home_subtitle_description_format=0x7f060002;
    public static final int abc_action_bar_up_description=0x7f060003;

We access a resource in two ways, in code using R.string.hello and in XML using @string/hello


External library files will be placed in this folder. If you want any external library in your project, place the library jar inside this folder and it will be added to the classpath automatically.


This file contains metadata that describes our application ot the OS. File is always named AndroidManifest.xml and lives in the root directory of our project.

When creating new activities, we need to add it to our AndroidManifest file so our OS can access it. The dot at the start of this attribute’s value tells the OS that this activity’s class is in the package specified in the package attribute in the manifest element at the top of the file.

<manifest xmlns:android=""
          package="net.shawnklein.carpk.testapp" >
        <activity android:name=".MainActivity"
                  android:label="@string/app_name" />
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>

This file also tells the OS which Activity is the launcher activity, that is the activity that first starts when the OS calls on the application. The manifest declaration specifies this with intent-filter element.


These files hold the code that preforms the functionality we need our app to accomplish.


This directory is home to our xml and png resources.

Resources are images, audio, and XML files that live in the res/ diretory. We use the resource ID R.layout.activity_main to access these files. This ID returns an int set from class layout in, this looks something like public static final int activity_main=0x7f04001a;.


References to a string will begin with @string/ and refrences for a drawable will begin with @drawable/. Drawable resorces have differant files for different dpi screens. See the section below for an undestanding of which each file is used for. This folder is initally empty, but you can upload an image by right clicking res folder and selecting new image asset. Android Studio will create the appropriate resolutions from the uploaded image you provide.


These files hold the images for your app/launcher icons. The launcher icon is used at different resolutions from the device's current density.

  • mdpi medium density screens(~160dpi)
  • hdpi high density screens(~240dpi)
  • xhdpi extra high density screens(~320dpi)
  • xxhdpi extra extra high density screens(~480dpi)
  • xxxhdpi extra extra extra high density screens(~640dpi)

They are refrenced as android:icon="@mipmap/ic_launcher".


These files hold widgets that interprept what our activities will look like. If no 'layout-landorlayout-portdirectory is available, Android will default to this directory and use thexml` files located here.


Android keeps all the strings all in one place, the strings.xml file. References to a string value will begin with @string/ followed by the resource name.

// strings.xml
  <string name="hello_toast">Hi there!</string>