My Life with Android
Introduction Android Componets UserInterface Advanced UI Data Storage Advanced Concepts Others New Studio

Project Structure

Once your project is created successfully, you will have following project screen.


Folder, File Description
src This contains the .java source files for your project. By default, it includes an MainActivity.java source file having an activity class that runs when your app is launched using the app icon.
gen This contains the .R file, a compiler-generated file that references all the resources found in your project. You should not modify this file.
bin This folder contains the Android package files .apk built by the ADT during the build process and everything else needed to run an Android application.
res/drawable-hdpi This is a directory for drawable objects that are designed for high-density screens.
res/layout This is a directory for files that define your app's user interface.
res/values This is a directory for other various XML files that contain a collection of resources, such as strings and colours definitions.
AndroidManifest.xml This is the manifest file which describes the fundamental characteristics of the app and defines each of its components.

Android Manifest

Whatever component you develop as a part of your application, you must declare all its components in a manifest.xml which resides at the root of the application project directory. This file works as an interface between Android OS and your application, so if you do not declare your component in this file, then it will not be considered by the OS. 
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.helloworld"
   android:versionCode="1"
   android:versionName="1.0" >
   
   <uses-sdk
      android:minSdkVersion="8"
      android:targetSdkVersion="22" />
   
   <application
       android:icon="@drawable/ic_launcher"
       android:label="@string/app_name"
       android:theme="@style/AppTheme" >
       
       <activity
          android:name=".MainActivity"
          android:label="@string/title_activity_main" >
       
          <intent-filter>
             <action android:name="android.intent.action.MAIN" />
             <category android:name="android.intent.category.LAUNCHER"/>
          </intent-filter>
       
       </activity>
       
   </application>
</manifest>
  • Here <application>...</application> tags enclosed the components related to the application.
  • Attribute android:icon will point to the application icon available under res/drawable-hdpi. The application uses the image named ic_launcher.png located in the drawable folders.
  • The <activity> tag is used to specify an activity and android:name attribute specifies the fully qualified class name of the Activity subclass.
  • The android:label attributes specifies a string to use as the label for the activity.
  • Note:You can specify multiple activities using <activity> tags.
  • The action for the intent filter is named android.intent.action.MAIN to indicate that this activity serves as the entry point for the application. The category for the intent-filter is named android.intent.category.LAUNCHER to indicate that the application can be launched from the device's launcher icon.

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