Now you will be creating your first Android Activity here.Here examines the application-building process from start to finish. I will show you how to create an Android project in Eclipse, add code to the initial files, and run the finished application in the Android Emulator. The resulting application will be a fully functioning program running in an Android environment.
Actually, as you move through this excercise, you will be creating more than one Android Activity. Computer programming tradition dictates that your first application be the typical Hello World! application, so in the first section you will create a standard Hello World! application with just a blank background and the “Hello World!” text. Then, for the sake of enabling you to get to know the language better, the next section explains in detail the files automatically created by Android for your Hello World! application. You will create two iterations of this Activity, each using different techniques for displaying information to the screen. You will also create two different versions of a Hello World! application that will display an image that delivers the “Hello World!” message. This will give you a good introduction to the controls and inner workings
of Android.
NOTE
You will often see “application” and “Activity” used interchangeably. The difference between the two is that an application can be composed of multiple Activities, but one application must have at least one Activity. Each “window” or screen of your application is a separate Activity. Therefore, if you create a fairly simple application with only one screen of data (like the Hello World! application in previous Posts), that will be one Activity. In future Posts you will create applications with multiple Activities.
To make sure that you get a good overall look at programming in Android, create both of these applications in the Android SDK command-line environment for Microsoft Windows and Linux. In other words, this here covers the creation process in Eclipse, and we covers the creation process using the command-line tools. Therefore, before continuing, you should check that your Eclipse environment is correctly configured. Review the steps in post for setting the PAT statement for the Android SDK. You should also ensure that the JRE is correctly in you PATH statement.
TIP
If you have configuration-related issues while attempting to work with any of the command-line examples, try referring to the configuration steps in before ; and look at the Android SDK documentation.
