Getting Started with Android

All you need to start writing your own Android applications is a copy of the Android SDK and the Java development kit. Unless you’re a masochist, you’ll probably want a Java IDE — Eclipse is particularly well supported — to make development a little easier.

Versions of the SDK, Java, and Eclipse are available for Windows, Mac OS, and Linux, so you can explore Android from the comfort of whatever OS you favor. The SDK includes an emulator for all three OS environments, and because Android applications are run on a virtual machine, there’s no advantage to developing from any particular operating system.

Android code is written using Java syntax, and the core Android libraries include most of the features from the core Java APIs. Before they can be run, though, your projects are first translated into Dalvik byte code. As a result, you get the benefits of using Java, while your applications have the advantage of running on a virtual machine optimized for Android devices.

The SDK download includes all the Android libraries, full documentation, and excellent sample applications. It also includes tools to help you write and debug your applications, like the Android Emulator to run your projects and the Dalvik Debug Monitoring Service (DDMS) to help debug them.

By the end of this chapter, you’ll have downloaded the Android SDK, set up your development environment, completed two new applications, and run and debugged them using the emulator and DDMS.

If you’ve developed for mobile devices before, you already know that their small-form factor, limited power, and restricted memory create some unique design challenges. Even if you’re new to the game, it’s obvious that some of the things you can take for granted on the desktop or the Web aren’t going to work on a mobile.

As well as the hardware limitations, the user environment brings its own challenges. Mobile devices are used on the move and are often a distraction rather than the focus of attention, so your applications need to be fast, responsive, and easy to use.

The Android SDK includes all the tools and APIs you need to write compelling and powerful mobile applications. The biggest challenge with Android, as with any new development toolkit, is learning the features and limitations of its APIs.

If you have experience in Java development, you’ll find that the techniques, syntax, and grammar you’ve been using will translate directly into Android, although some of the specific optimization techniques may seem counterintuitive.

If you don’t have experience with Java but have used other object-oriented languages (such as C#), you should find the transition straightforward. The power of Android comes from its APIs, not from Java, so being unfamiliar with all the Java specific classes won’t be a big disadvantage.

Because Android applications run within the Dalvik virtual machine, you can write them on any platform that supports the developer tools. This currently includes the following:

To get started, you’ll need to download and install the following:

You can download the latest JDK from Sun at

http://java.sun.com/javase/downloads/index.jsp

The SDK is presented as a ZIP fi le containing the API libraries, developer tools, documentation, and several sample applications and API demos that highlight the use of particular API features. Install it by unzipping the SDK into a new folder. (Take note of this location, as you’ll need it later.)

The examples and step-by-step instructions provided are targeted at developers using Eclipse with the Android Developer Tool (ADT) plug-in. Neither is required, though — you can use any text editor or Java IDE you’re comfortable with and use the developer tools in the SDK to compile, test, and debug the code snippets and sample applications.

Using Eclipse with the ADT plug-in for your Android development offers some significant advantages.

Eclipse is an open source IDE (integrated development environment) particularly popular for Java development. It’s available to download for each of the development platforms supported by Android (Windows, Mac OS, and Linux) from the Eclipse foundation homepage:

www.eclipse.org/downloads/

There are many variations available when selecting your Eclipse download; the following is the recommended configuration for Android:

WST and the JDT plug-in are included in most Eclipse IDE packages.

Installing Eclipse consists of uncompressing the download into a new folder. When that’s done, run the Eclipse executable. When it starts for the first time, create a new workspace for your Android development.

The ADT plug-in for Eclipse simplifies your Android development by integrating the developer tools, including the emulator and .class-to-.dex converter, directly into the IDE. While you don’t have to use the ADT plug-in, it does make creating, testing, and debugging your applications faster and easier.

The ADT plug-in integrates the following into Eclipse:

Figure 2-1 shows the DDMS perspective within Eclipse with the ADT plug-in installed.

Install the developer tools plug-in by the following steps:

As the Android SDK matures, there are likely to be frequent updates to the ADT plug-in. In most cases, to update your plug-in, you simply: