In Chapter 1, you downloaded the Java SE, Eclipse, and Android SDK packages you need to build an environment for creating Android applications. In Chapter 3, you'll learn how to set up the tools you'll use throughout the rest of the book. You'll do this by creating, step by step, from scratch, the very latest Android IDE out there—right on your very own development workstation.

Note that part of this process must be done while online, so be sure to have your Internet connection active and firing on all cylinders. We'll be connecting in real time, via Google's Android Developers web site, to the latest Android application development tools, plug-ins, drivers, and documentation.

Although it might seem that the setup of Java SE, Eclipse IDE, Android's SDK, and an Android Virtual Device (an emulator that mimics the behavior of a real Android smartphone) is a topic too trivial for an entire chapter, that task is actually one of the most critical in this book. If your IDE does not work 100% perfectly, your code will not work 100% perfectly. In fact, without a robust and properly configured IDE, you may not be able to develop any code at all!

The Eclipse IDE is a sophisticated programming environment that features code highlighting, device emulation, logic tracing, debugging, and a plethora of other features. Figure 2-1 shows an example of working in Eclipse, and Figure 2-2 shows an Android Virtual Device in action.

Figure 2.1. The Eclipse IDE

Figure 2.2. An Android Virtual Device (AVD) in action

In Chapter 3, you will learn how to customize the Eclipse IDE with Android plug-ins, which will morph the tool into one tailored to the particular needs of an Android developer like you. As you will see, setting up this IDE for your specific development goals is not a trivial undertaking.

As you'll learn in Chapter 4, an Android application is "stratified." Its functionality is spelled out in Java code, XML markup, and the Android manifest in a way that is truly unique. This adds a great deal of extensibility, or development flexibility, to applications. Android makes heavy use of an XML-based markup language to define the basic components of an application, especially its visual components. Markup is not technically code, but rather consists of tags, similar to the HTML tags web developers use to format their online documents. XML is used in Android to define everything from UIs to data access, and even programmatic constructs like Java object definitions and configurations.

XML markup tags are easier for beginners to comprehend than a complex programming language like Java. For this reason, you'll use XML throughout this book whenever possible, as Google recommends. Here, you'll get a basic beginning knowledge of Android application development, yet this will still give you the ability to make your apps look very elegant and professional. I call it getting the maximum return on your investment, and XML makes this possible.

By the time you reach Chapter 5, you'll have built a rock-solid integrated Android software development environment and acquired a basic understanding of the components that make up an application development project (images, text, layout, buttons, code, audio, video, animation, XML, and so on).

In Chapter 5, you'll learn the unique lingo of Android application design—that is, what the various components of an Android application are called.

I'll outline how Java programming code and XML, along with any new media resources, are compiled, compressed, and bundled into Android's signature .apk file type (APK stands for Android PacKage), and how logical Android components talk to each other in an application.

The chapter also provides an overview of Android activities, which define the user experience on the screen, and explains how they operate. You'll learn about Android services as well, which run in the background, separate from the application's activities, and provide the user with advanced functions through the UI.

You'll also take an initial look at broadcast receivers, which alert an Android application to events of interest, such as the activation of a camera on an Android device or an incoming phone call. In fact, your app can even send out its own broadcasts, if there is some reason to let other applications know of a change in state in one of your application's data constructs.

The chapter finishes up with a look at content providers, which are often databases filled with information, such as a contact list, that applications may want to access to provide functionality of their own. Android ships with a number of preconfigured content providers, and you can also write your own.

By Chapter 6, you will have a better idea of how the Android operating system works internally, and how it wants to see applications put together. You'll be ready to design graphics, UIs, and even user experiences for your applications.

You'll do all of this using screen constructs called views and view groups (grouped views) and flexible layout containers, which can all be nested within each other to create the UI your application needs.

Chapter 6 explains how the display screen—the way most users interact with an Android application—is handled in Android with a mixture of Java code and XML markup that controls the hierarchy of View and ViewGroup objects and Layout containers. You can also extend these classes to create your own custom View objects and Layout containers when you need a more complex design. These containers ultimately hold the other visual and UI content in your application in its proper place, and thus are the foundation of your application design. You'll want to learn these screen view and layout concepts thoroughly, as they are core to implementing everything else that Android can do.

You'll revisit XML yet again in this chapter, and learn how it allows you to define complex screen layouts and UI designs without writing a single line of Java code. You'll learn about the different types of layout containers, and how each can be useful in different UI design scenarios, and even code a really cool application that is written almost completely with XML.

In Chapter 7, we'll start building usable UI designs, using the XML foundation of the previous chapters, via your screen layout and view control.

We'll cover the three main screen resolutions that you can design UIs for under Android and which options you have for providing high-, medium-, and low-resolution graphics to allow Android to fit your application to each major screen size. We'll also cover the creation of standardized Android icons for use in your UI designs.

Android has a large number of UI elements, such as buttons, text fields, radio buttons, check boxes, menus, alert dialogs, and all of those familiar controls that allow users to interface with application software. These items can be implemented both in Java and in XML.

In Chapter 7, we'll design and code a usable application. We'll design views, layouts, and UI elements, as well as attach their XML design elements to Java code that performs some simple functions when the UI elements are used by the application's users.

We'll look at the differences between option menus and context-sensitive menus, as well as submenus for both of these types of menu constructs. We'll also review different types of dialog boxes, such as alert dialogs, progress dialogs, and dialogs for picking dates and times.

In Chapter 8, we'll start adding application media elements through images, video, and animation. These elements are key to making your application look great across all Android phones.

The Android smartphone Active-Matrix Organic Light-Emitting Diode (AMOLED) half-size video graphics array (HVGA) and wide video graphics array (WVGA) screens on current products are impressive enough these days to allow some amazing experiences to be created, so this is where it starts to get interesting as far as the visuals are concerned.

In Chapter 8, we'll explore the following:

In Chapter 9, we'll talk about adding interactivity to applications, so that they respond to user input and actually do something. You do this by handling UI events. We'll look at the most efficient way of handing events that are triggered by your users using the UI elements that are attached to the views and layouts defined in your XML files.

The following topics are covered:

In Chapter 10, we'll be ready to get into the complexity of accessing data structures and Android content providers. These content providers allow you to access databases of system information that are available through the Android operating system, as well as your own databases of information.

Content providers are the only method Android provides for sharing data across applications, which is why they are important enough to merit their own chapter. We'll take a close look at the features of Android that allow you to query data from items common to the Android platform, such as images, video, audio, and contacts.

Additionally, you can create your own content providers or add data to one. You'll see how to create a content resolver so that you can interface with whatever content providers you choose (and have permissions to access).

You'll learn about how content providers expose their data via data models similar to databases, and how to use cursors to traverse the database in various ways.

Finally, we'll investigate URI objects and how to use them to identify and access data sets. Each set of data in the database will have its own Uniform Resource Identifier (URI), which is similar to an HTTP URL.

In Chapter 11, we are going to tackle one of the more complex concepts in the Android environment: intents. Intents are asynchronous messages (members of the Intents class) that travel between Android's activities, services, and broadcast receiver components. Asynchronous means not synchronized; that is, messages can be sent and received independently (not in sync, but without pattern or reason) from each other.

Using intents allows you to take your current Android applications to an entirely new level of complexity. Prior to this chapter, you'll have added functionality to your application by accessing the cool functions that Android provides. But all easy things must come to an end, so they say.

Armed with intents (no pun intended), you can create advanced programming logic of your own that ties together everything you have learned in the previous chapters. This allows for far more powerful and useful programming constructs, and takes you from beginner to intermediate.

You'll learn how to spawn Intent objects that can carry highly customized messages back and forth between your Android UI (activities) and your programming logic (services) for instance, as well as to and from broadcast receiver components.

We'll also look at intent resolution and intent filters. These allow you to filter out events that your apps do not need to be concerned with, allowing you to optimize the progress of internal communications.

In the final chapter, I will expose you to all of those fascinating areas within the Android development environment that we did not have the bandwidth to cover in this book. There may be a lot of unfamiliar names and acronyms in this description, but that's the nature of the future of Android.

The 3D engine inside Android is called OpenGL ES 1.2. You'll see how it allows you to create real-time rendered 3D games and applications. And I'll give you some great resources to find out more about this powerful 3D engine.

The SQLite database exists inside the Android operating system. We'll uncover the power it offers in allowing client-side databases to be created and used as content providers.

Smartphone hardware such as the high-definition camera, GPS, accelerometer, and microphone can be used to capture and digitize real-world events around us as images, audio, and gestures, and turn them into data that can be used in your applications. Computer programming has never been so powerful and innovation-oriented.

Inter-Android communication is another hot area, especially since Android devices can be used as wireless hubs, giving access to many. We will look at Android's integrated Bluetooth APIs, which allow Android applications to wirelessly connect with any Bluetooth device, and even provide for multiple connections.

We'll cover the concept of creating app widgets, or miniature applications that can be embedded in other applications (think: the Android home screen) and receive real-time updates (for things like clocks, radios, and weather stations).

Finally, we'll consider the popular area of locations and maps using the Android location package and Google Maps as an external data library. These tools are valuable for Android application development, due to the mobile nature of the smartphone and the fact that it has a built-in GPS.

As you can see from this chapter, this book will take you on a wild journey through the various parts and components of the Android operating environment—from UI design, to new media assets, to database access, to more complicated background services and interapplication messaging. We'll be dealing with adding some pretty cool elements to Android applications, mainly by leveraging the power of "design via XML" and some of Android's built-in features.

In the next chapter, you'll build an Eclipse-based Android IDE using the software that you downloaded at the end of Chapter 1. After that, you'll learn about how the Android development environment is modularized and how to set it up to create applications using this diverse mobile operating system.