Android Development Intro

Applications

Android applications are software programs that can run on the Android operating system. Most Android-powered devices are purchased with a selection of basic apps already installed. Users can then download any number of additional apps. The Android Market divides applications into a number of categories, including games, reference, business, entertainment, communication, media, shopping and productivity among many others. Developers can therefore design applications for a wide variety of functions.

Development Process

The Android development process results in the production of an APK file, which is an Android Package File. An APK file represents the final exported version of an app, which users can access through the Market. To create a functioning APK file, developers use the Eclipse IDE (Integrated Development Environment) in conjunction with the Android SDK (Software Development Kit) and ADT (Android Developer Tools) plugin. These tools allow developers to code, compile, test and finally export Android apps. Developers can see their apps running on virtual devices using the AVD (Android Virtual Device) Manager.

Technologies

Android applications can involve multiple technologies, but in most cases they are mainly built using Java and XML coding. The XML for an application can model data and visual items such as user interface designs. Android developers use XML to define the layouts users see when they launch an application. The Java code for an Android app defines the logic and processing within it. Using Java classes, developers can define each application element with properties and behavior delivering the app's functionality. Developers who are learning Android but are not already familiar with the Java language often have to educate themselves about basic aspects of the technology, including objects and inheritance.

Releasing

When a developer finishes building and testing an Android application and is ready to release it through the Android Market, they need to go through a series of steps. The Android Market requires applications to be signed and versioned according to specific guidelines. Developers therefore need to secure their APK files using an encryption process, using the same key for each version of an app. The application manifest file allows developers to indicate versions with incrementing version numbers for each release. Developers can decide whether to charge a fee for their apps or whether to release them for free. Some developers release both free and paid versions of their apps, with the free versions sometimes supported by advertising.