ANDROID APPLICATION DEVELOPMENT
Whether youāre an experienced mobile engineer, a desktop or web developer, or a complete programming novice, Android represents an exciting opportunity to write applications for an audience of over two billion Android device users.
Youāre probably already familiar with Android, the most common software powering mobile phones. If not, and you purchased this book in the hope that Android development would help you create an unstoppable army of emotionless robot warriors on a relentless quest to cleanse the earth of the scourge of humanity, you should reconsider this book purchase (and your life choices.)
When announcing Android at its launch in 2007, Andy Rubin described it as follows:
Since then, Android has expanded beyond mobile phones to provide a development platform for an increasingly wide range of hardware, including tablets, televisions, watches, cars, and Internet-of-Things (IoT) devices.
Android is an open source software stack that includes an operating system, middleware, and key applications for mobile and embedded devices.
Critically, for us as developers, it also includes a rich set of API libraries that make it possible to write applications that can shape the look, feel, and function of the Android devices on which they run.
In Android, system, bundled, and all third-party applications are written with the same APIs and executed on the same run time. These APIs feature hardware access, video recording, location-based services, support for background services, maps, notifications, sensors, relational databases, inter-application communication, Bluetooth, NFC, and 2D and 3D graphics.
This book describes how to use these APIs to create your own Android applications. In this chapter you learn some guidelines for mobile and embedded hardware development, and are introduced to some of the platform features available to Android developers.
Android has powerful APIs, a huge and diverse ecosystem of users, excellent documentation, a thriving developer community, and has no required costs for development or distribution. As the Android device ecosystem continues to grow, you have the opportunity to create innovative applications for users, no matter what your development experience.
A LITTLE BACKGROUND
In the days before Instagram, Snapchat, and PokĆ©mon Go, when Google was still a twinkle in its foundersā eyes and dinosaurs roamed the earth, mobile phones were just thatāportable phones small enough to fit inside a briefcase, featuring batteries that could last up to several hours. They did, however, offer the freedom to make calls without being physically connected to a landline.
In the 10 years since the first Android device was launched, smart phones have become ubiquitous and indispensable. Hardware advancements have made devices more powerful, featuring bigger, brighter screens and featuring advanced hardware including accelerometers, fingerprint scanners, and ultra-high-resolution cameras.
These same advances have more recently resulted in a proliferation of additional form factors for Android devices, including a large variety of smart-phones, tablets, watches, and televisions.
These hardware innovations offer fertile ground for software development, providing many opportunities to create innovative new applications.
The Not-So-Distant Past
In the early days of native phone application development, developers, generally coding in low-level C or C++, needed to understand the specific hardware they were coding for, typically a single device or possibly a range of devices from a single manufacturer. The complexity inherent in this approach meant the applications written for these devices often lagged behind their hardware counterparts. As hardware technology and mobile Internet access have advanced, this closed approach has become outmoded.
The next significant advancement in mobile phone application development was the introduction of Java-hosted MIDlets. MIDlets were executed on a Java virtual machine (JVM), a process that abstracted the underlying hardware and let developers create applications that ran on many devices that supported the Java run time.
Unfortunately, this convenience came at the price of more heavily restricted access to the device hardware. Similarly, it was considered normal for third-party applications to receive different hardware access and execution rights from those given to native applications written by the phone manufacturers, with MIDlets often receiving few of either.
The introduction of Java MIDlets expanded developersā audiences, but the lack of low-level hardware access and sandboxed execution meant that most mobile applications were regular desktop programs or websites designed to render on a smaller screen, and didnāt take advantage of the inherent mobility of the handheld platform.
Living in the Future
At its introduction, Android was part of a new wave of modern mobile operating systems designed specifically to support application development on increasingly powerful mobile hardware.
Android offers an open development platform built on an open source Linux kernel. Hardware access is available to all applications through a series of API libraries, and application interaction, while carefully controlled, is fully supported.
In Android, all applications have equal standing. Third-party and native Android applications are written with the same APIs and are executed on the same run time. Users can replace most system application with a third-party developerās alternative; indeed, even the dialer and home screens can be replaced.
