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:
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.
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.
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 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.