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Friday, 31 May 2013

Architecture of Android

Architecture of Android

Architecture of Android

In order to understand how Android works, take a look at below  Figure  , which shows the various layers that make up the Android operating system (OS).

The Android OS is roughly divided into five sections in four main layers:

➤➤ Linux kernel — This is the kernel on which Android is based. This layer contains all the lowlevel device drivers for the various hardware components of an Android device.

➤➤ Libraries — These contain all the code that provides the main features of an Android OS. For example, the SQLite library provides database support so that an application can use it for data storage. The WebKit library provides functionalities for web browsing.

➤➤  Android runtime — At the same layer as the libraries, the Android runtime provides a set of core libraries that enable developers to write Android apps using the Java programming language. The Android runtime also includes the Dalvik virtual machine, which enables every Android application to run in its own process, with its own instance of the Dalvik virtual machine (Android applications are compiled into the Dalvik executables). Dalvik is a specialized virtual machine designed specifically for Android and optimized for battery-powered mobile devices with limited memory and CPU.

➤➤ Application framework — Exposes the various capabilities of the Android OS to application developers so that they can make use of them in their applications.

➤➤ Applications — At this top layer, you will find applications that ship with the Android device (such as Phone, Contacts, Browser, etc.), as well as applications that you download and install from the Android Market. Any applications that you write are located at this layer.

Android Devices in the Market

 Android devices come in all shapes and sizes. As of late November 2010, the Android OS can be seen powering the following types of devices:
➤➤ Smartphones
➤➤ Tablets
➤➤ E-reader devices
➤➤ Netbooks
➤➤ MP4 players
➤➤ Internet TVs

Chances are good that you own at least one of the preceding devices. Above Figure  shows (clockwise) the Samsung Galaxy S, the HTC Desire HD, and the LG Optimus One smartphones.

Another popular category of devices that manufacturers are rushing out is the tablet. Tablet sizes typically start at seven inches, measured diagonally. Figure 1-3 shows the
Samsung Galaxy Tab and the Dell Streak, which is a fiveinch phone tablet.

In addition to these popular mobile devices, Android is also slowly finding its way into your living room. People of Lava, a Swedish company, has developed an Android-based TV, call the Scandinavia Android TV (see below Figure).
Google has also ventured into a proprietary smart TV platform based on Android and co-developed with companies such as Intel, Sony, and Logitech. Figure 1-6 shows Sony’s Google TV.

The Android market

As mentioned earlier, one of the main factors determining the success of a smartphone platform is the applications that support it. It is clear from the success of the iPhone that applications play a very vital role in determining whether a new platform swims or sinks. In addition, making these applications accessible to the general user is extremely important. As such, in August 2008, Google announced the Android Market, an online application store for Android devices, and made it available to users in October 2008. Using the Market application that is preinstalled on their Android device, users can simply download third-party applications directly onto their devices. Both paid and free applications are supported on the Android Market, though paid applications are available only to users in certain countries due to legal issues.

Similarly, in some countries, users can buy paid applications from the Android Market, but developers cannot sell in that country. As an example, at the time of writing, users in India can buy apps from the Android Market, but developers in India cannot sell apps on the Android Market. The reverse may also be true; for example, users in South Korea cannot buy apps, but developers in South Korea can sell apps on the Android Market.

Obtaining the required tools Now that you know what Android is and its feature set, you are probably anxious to get your hands dirty and start writing some applications! Before you write your fi rst app, however, you need to download the required tools and SDKs.

For Android development, you can use a Mac, a Windows PC, or a Linux machine. All the tools needed are free and can be downloaded from the Web. Most of the examples provided in this book should work fine with the Android emulator, with the exception of a few examples that require access to the hardware.

 Let's using a Windows 7 computer to demonstrate all the code samples. If you are using a Mac or Linux computer, the screenshots should look similar; some minor differences may be present, but you should be able to follow along without problems.
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Monday, 20 May 2013

Most Features of Android

Features of Android

As Android is open source and freely available to manufacturers for customization, there are no fixed hardware and software configurations. However, Android itself supports the following features:

➤➤ Storage — Uses SQLite, a lightweight relational database, for data storage. Chapter 6 discusses data storage in more detail.

➤➤ Connectivity — Supports GSM/EDGE, IDEN, CDMA, EV-DO, UMTS, Bluetooth (includes A2DP and AVRCP), WiFi, LTE, and WiMAX. Chapter 8 discusses networking in more detail.

➤➤ Messaging — Supports both SMS and MMS. Chapter 8 discusses messaging in more detail.

➤➤ Web browser — Based on the open-source WebKit, together with Chrome’s V8 JavaScript engine

➤➤ Media support — Includes support for the following media: H.263, H.264 (in 3GP or MP4 container), MPEG-4 SP, AMR, AMR-WB (in 3GP container), AAC, HE-AAC (in MP4 or
3GP container), MP3, MIDI, Ogg Vorbis, WAV, JPEG, PNG, GIF, and BMP

➤➤ Hardware support — Accelerometer Sensor, Camera, Digital Compass, Proximity Sensor, and GPS

➤➤ Multi-touch — Supports multi-touch screens

➤➤ Multi-tasking — Supports multi-tasking applications

➤➤ Flash support — Android 2.3 supports Flash 10.1.

➤➤ Tethering — Supports sharing of Internet connections as a wired/wireless hotspot
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getting Started with Android Programming

getting ,Started ,with
Android, Programming

What Is Android?

Android is a mobile operating system that is based on a modified version of Linux. It was originally developed by a startup of the same name, Android, Inc. In 2005, as part of its strategy to enter the mobile space, Google purchased Android and took over its development work (as well as its development team). 

Google wanted Android to be open and free; hence, most of the Android code was released under the open-source Apache License, which means that anyone who wants to use Android can do so by downloading the full Android source code. Moreover, vendors (typically hardware manufacturers) can add their own proprietary extensions to Android and customize Android to differentiate their products from others. This simple development model makes Android very attractive and has thus piqued the interest of many vendors. This has been especially true for companies affected by the phenomenon of Apple’s iPhone, a hugely successful product that revolutionized the smartphone industry.

Such companies include Motorola and Sony Ericsson, which for many years have been developing their own mobile operating systems. When the iPhone was launched, many of these manufacturers had to scramble to find new ways of revitalizing their products. These manufacturers see Android as a solution — they will continue to design their own hardware and use Android as the operating system that powers it.

The main advantage of adopting Android is that it offers a unified approach to application development. Developers need only develop for Android, and their applications should be able to run on numerous different devices, as long as the devices are powered using Android. In the world of smartphones, applications are the most important part of the success chain. Device manufacturers therefore see Android as their best hope to challenge the onslaught of the iPhone, which already commands a large base of applications.
Android Versions Android has gone through quite a number of updates since its first release.  

Android Version
Release Date
9 February 2009

30 April 2009
15 September 2009
26 October 2009
May 2010
6 December 2010

Unconfirmed at the time of writing

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