Android
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The document discusses the architecture and benefits of the Android mobile operating system. It explains that Android addresses the growing needs of mobile users and developers by providing an open platform with built-in services, automatic application management, and portability across devices. The key components of the Android architecture include the Linux kernel, native libraries, Dalvik virtual machine, application framework, and applications/widgets layer. Android benefits developers by being free, open source, and not locked to any single vendor.
Android
- 1. Introduction The mobile development is becoming the standard of the industry application. Mobile users demand more choice, more opportunities to customize their phones and tablets with more functionality. Mobile Service Providers and operators want to provide value-added content to their subscribers in a manageable and lucrative way. Mobile developers want the freedom to develop the powerful mobile applications users demand with minimal roadblocks to success. Finally, handset manufacturers want a stable, secure, and affordable platform to power their devices. Android is one of the potential game changer for the mobile development and is addressing the growing needs of the mobile marketplace. This chapter explains the architecture of Android OS and its benefits. Objectives At the end of this module, the students will be able to: 1.1. Explain the benefits of Android OS 1.2. Analyze the architecture of Android 1.1 Android OS and its benefits Google’s Android mobile phone software platform is the next big opportunity for application software developers. Google announced the Open Handset Alliance and the Android platform in November of 2007, releasing the first beta version of the Android Software Development Kit (SDK) at the same time. As per the statistics of Google more than 1 million people had downloaded the versions of the SDK.lso Android, by providing a standard mobile phone application environment, it has also provided a market (Google Play) for mobile applications—and the opportunity for applications developers to profit from those applications. Proprietary Software Stacks Most of the existing smart phones and tablets use proprietary, relatively closed software stacks, such as Nokia’s Series with the Symbian operating system as well as with Windows Operating System and Apple IOS. Modifications to these stacks (adding a driver, for example) have to be done either by the stack owner or by the handset manufacturer. The stacks are not open source, so changing anything in the stack is difficult at best
- 2. Closed networks Mobile operators often lock the handsets so applications cannot be added. The operators claim this is needed to preserve the integrity of their mobile networks, making sure that viruses and spam are not inadvertently installed by end users. The Open Handset Alliance Google and 33 other companies announced the formation of the Open Handset Alliance on November 5, 2007. For us as mobile application developers, that means we are free to develop whatever creative mobile applications we can think of, free to market them (or give them, at our option) to Android mobile phone owners, and free to profit from that effort any way we can. Each member of the Open Handset Alliance has its own reasons for participating and contributing its intellectual property, and we are free to benefit. The Alliance releases software through Google’s developer website (http://developer.android.com). Features of Android There are already many mobile platforms on the market today, including Symbian, iPhone, Windows Mobile, BlackBerry, Java Mobile Edition, Linux Mobile (LiMo), and more but Android is the first environment that combines the following: • A truly open, free development platform based on Linux and open source: Handset makers like it because they can use and customize the platform without paying a royalty. Developers like it because it is not locked into any one vendor that may go under or be acquired. • Tons of built-in services out of the box: Location-based services use GPS or cell tower triangulation. A full-powered SQL database lets the power of local storage for occasionally connected computing and synchronization. Browser and map views can be embedded directly in the applications. All these built-in capabilities helps in lowering the development costs. • Automatic management of the application life cycle: Programs are isolated from each other by multiple layers of security, which will provide a level of system stability not seen before in smart phones. The end user will no longer have to worry about what applications are active or close some programs so that others can run. Android is optimized for low-power, low-memory devices
- 3. in a fundamental way that no previous platform has attempted. • High-quality graphics and sound: Smooth 2D vector graphics and animation inspired by Flash are melded with 3D accelerated OpenGL graphics to enable new kinds of games and business applications. Codecs for the most common industry standard audio and video formats are built right in, including H.264 (AVC), MP3, and AAC. • Portability across a wide range of current and future hardware: All the programs are written in Java and executed by Android’s Dalvik virtual machine, so the code will be portable across ARM, x86, and other architectures. Support for a variety of input methods is included such as keyboard, touch, and trackball. User interfaces can be customized for any screen resolution and orientation. Android Platform Android is an operating system and a software platform upon which applications are developed. A core set of applications for everyday tasks, such as web browsing and email, are included on Android handsets. The Android platform is designed to be more fault-tolerant than many of its predecessors. The handset runs a Linux operating system upon which Android applications are executed in a secure fashion. Each Android application runs in its own virtual machine. Android applications are managed code; therefore, they are much less likely to cause the phone to crash, leading to fewer instances of device corruption (also called “bricking” the phone, or rendering it useless). Android is open source software stack. The components and key layers of Android Platform are described in Figure 1.1 Linux Kernel Android is built on top of a solid and proven foundation: the Linux kernel. Android uses Linux for its memory management, process management, networking, and other operating system services.
- 4. Figure 1.1: Android System Architecture Native Libraries The next layer above the kernel contains the Android native libraries. These shared libraries are all written in C or C++, compiled for the particular hardware architecture used by the phone, and preinstalled by the phone vendor. Some of the most important native libraries include the following: • Surface Manager: Android uses a compositing window manager. It is simple, instead of drawing directly to the screen buffer, your drawing commands go into off screen bitmaps that are then combined with other bitmaps to form the display the user sees. This lets the system create all sorts of interesting effects such as see-through windows and fancy transitions. • 2D and 3D graphics: Two- and three-dimensional elements can be combined
- 5. in a single user interface with Android. The library will use 3D hardware if the device has it or a fast software renderer if it doesn’t have it. • Media codecs: Android can play video and record and play back audio in a variety of formats including AAC, AVC (H.264), H.263, MP3, and MPEG-4. • SQL database: Android includes the lightweight SQLite database engine, the same database used in Firefox and the Apple iPhone. You can use this for persistent storage in your application • Browser engine: For the fast display of HTML content, Android uses the WebKit library. This is the same engine used in the Google Chrome browser, Apple’s Safari browser, the Apple iPhone, and Nokia platform. These libraries are not applications that stand by themselves. They exist only to be called by higher level programs. Starting in Android 1.5, you can write and deploy your own native libraries using the Native Development Toolkit (NDK). Android Runtime Also sitting on top of the kernel is the Android runtime, including the Dalvik virtual machine and the core Java libraries. The Dalvik VM is Google’s implementation of Java, optimized for mobile devices. All the code you write for Android will be written in Java and run within the VM. Dalvik differs from traditional Java in two important ways: • The Dalvik VM runs .dex files, which are converted at compile time from standard .class and .jar files. .dex files are more compact and efficient than class files, an important consideration for the limited memory and battery- powered devices that Android targets. • The core Java libraries that come with Android are different from both the Java Standard Edition (Java SE) libraries and the Java Mobile Edition (Java ME) libraries. Application Framework Sitting above the native libraries and runtime is the Application Framework layer. This layer provides the high-level building blocks that are used to create the applications.
- 6. The framework comes preinstalled with Android, but can also be extended it with custom components as needed. The most important parts of the framework are as follows: • Activity manager: This controls the life cycle of applications and maintains a common “backstack” for user navigation. • Content providers: These objects encapsulate data that needs to be shared between applications, such as contacts. • Resource manager: Resources are anything that goes with the program that is not code. • Location manager: An Android phone always knows where it is. • Notification manager: Events such as arriving messages, appointments, proximity alerts, alien invasions, and more can be presented in an unobtrusive fashion to the user. Applications and Widgets The highest layer in the Android architecture diagram is the Applications and Widgets layer. End users will see only these programs Applications are programs that can take over the whole screen and interact with the user. On the other hand, Widgets (sometimes called gadgets), only operate in a small rectangle of the Home screen application. When someone buys an Android phone, it will come prepackaged with a number of standard system applications, including the following: • Phone dialer • Email • Contacts • Web browser • Android Market Using the Android Market, the user will be able to download new programs to run on their phone. Chapter Summary Mobile software development has evolved over time. Android has emerged as a new mobile development platform, building on past successes and avoiding past failures of other platforms. Android was designed to empower the developer to write innovative
- 7. applications. The platform is open source, with no up-front fees, and developers enjoy many benefits over other competing platforms. In the next chapter we will the installation procedures for Android and how to write programs.