“Hello World” Android Application Source Code Description

Hello World Source Code Description

At last, Now it is time to start coding!  You need to know details about source code description for your “Hello World” android application. We will learn about auto eclipse generated code for your application. Go to the “src” folder. In this folder, you will find the package folder, open the HelloWorld.java file. You will see the default code for an Android Activity:

Execution Control Flow of an Android Application

As a beginner we need to know the complete execution control flow of an Android application. To understand the basic execution flow of an Android application, Lets take the  HelloWorld example for detailed explanation.

When we create a new Android project using eclipse, We can see some folders such as “src” ,”gen” , “Android 2.2″ , “assets” and “res” etc.

Directory Structure of an Android Application

Before going to discuss “HelloWorld” application from code prospective, We need to know directory structure of an android application. When we create a new android project from eclipse editor, we can see there are lots of directories created for android applications. Let’s us understand these directories. Let’s start from the top most directory is src directory.

Hello World Program Application in Android Using Eclipse

Hello World Program Application in Android Using Eclipse

Hello world program application in Android using eclipse. It is the first step when we develop any application in any language. Before we create an Android Hello World Project, we need to make Virtual Device. It means after we create the android application, where we will run and test our application? For this we have 2 options. One is a real android device and second option is a Virtual device (Device Emulator, which android provides by default), To setup the virtual device, we need to follow the below steps.

Android Fundamentals and Components

Android Fundamentals and Components

Before going to start development, we need to know about Android Fundamentals and Components, which we will use frequently while developing our android applications. From a developer’s perspective, some important building blocks / components of android are as bellow. Just have a look at them for now, we will discuss them in details latter on.

Android Architecture

Android System Architecture

Lets have a look at the below image, which represents the overall android architecture. This image will give you some basic idea about android OS design. Basically you will learn the overall control flow between different android layers. The below image gives us some idea how the entire android OS communicate through different layers.