WHAT IS ANDROID:
Android is an open source and Linux-based operating system for mobile devices such as smartphones and tablet computers. Android was developed by the Open Handset Alliance, led by Google, and other companies. Android offers a unified approach to application development for mobile devices which means developers need only develop for Android, and their applications should be able to run on different devices powered by Android.
The first beta version of the Android Software Development Kit (SDK) was released by Google in 2007 where as the first commercial version, Android 1.0, was released in September 2008.
On June 27, 2012, at the Google I/O conference, Google announced the next Android version, 4.1 Jelly Bean. Jelly Bean is an incremental update, with the primary aim of improving the user interface, both in terms of functionality and performance.
The source code for Android is available under free and open source software licenses. Google publishes most of the code under the Apache License version 2.0 and the rest, Linux kernel changes, under the GNU General Public License Version 2
Why Android
History of Embedded device programming:
An embedded system is a combination of computer hardware and software, either fixed in capability or programmable, designed for a specific function or functions within a larger system. Industrial machines, agricultural and process industry devices, automobiles, medical equipment, cameras, household appliances, airplanes, vending machines and toys, as well as mobile devices, are possible locations for an embedded system.
Embedded systems are computing systems, but they can range from having no user interface ( UI ) -- for example, on devices in which the system is designed to perform a single task -- to complex graphical user interfaces ( GUIs ), such as in mobile devices. User interfaces can include buttons, LEDs, touchscreen sensing and more. Some systems use remote user interfaces as well.
History of embedded systems
Embedded systems date back to the 1960s. Charles Stark Draper developed an integrated circuit ( IC ) in 1961 to reduce the size and weight of the Apollo Guidance Computer, the digital system installed on the Apollo Command Module and Lunar Module. The first computer to use ICs, it helped astronauts collect real-time flight data.
In 1965, Autonetics, now a part of Boeing, developed the D-17B, the computer used in the Minuteman I missile guidance system. It is widely recognized as the first mass-produced embedded system. When the Minuteman II went into production in 1966, the D-17B was replaced with the NS-17 missile guidance system, known for its high-volume use of integrated circuits. In 1968, the first embedded system for a vehicle was released; the Volkswagen 1600 used a  microprocessor  to control its electronic fuel injection system.
By the late 1960s and early 1970s, the price of integrated circuits dropped and usage surged. The first microcontrollerwas developed by Texas Instruments in 1971. The TMS 1000 series, which became commercially available in 1974, contained a 4-bit processor, read-only memory (ROM) and random-access memory ( RAM ), and cost around $2 apiece in bulk orders.
Also in 1971, Intel released what is widely recognized as the first commercially available processor, the 4004. The 4-bit microprocessor was designed for use in calculators and small electronics, though it required eternal memory and support chips. The 8-bit Intel 8008, released in 1972 had 16 KB of memory; the Intel 8080 followed in 1974 with 64 KB of memory. The 8080's successor, x86 series, was released in 1978 and is still largely in use today.
In 1987, the first embedded operating system, the real-time VxWorks, was released by Wind River, followed by Microsoft's Windows Embedded CE in 1996. By the late 1990s, the first embedded  Linux  products began to appear. Today, Linux is used in almost all embedded devices.
Embedded system hardware (microprocessor-based, microcontroller-based)
Embedded system hardware can be microprocessor- or microcontroller-based. In either case, an integrated circuit is at the heart of the product that is generally designed to carry out computation for real-time operations. Microprocessors are visually indistinguishable from microcontrollers, but while the microprocessor only implements a central processing unit (CPU) and, thus, requires the addition of other components such as memory chips, microcontrollers are designed as self-contained systems.
Microcontrollers include not only a CPU, but also memory and peripherals such as  flash memory , RAM or serial communication ports. Because microcontrollers tend to implement full (if relatively low computer power) systems, they are frequently put to use on more complex tasks. For example, microcontrollers are used in the operations of vehicles, robots, medical devices and home appliances, among others. At the higher end of microcontroller capability, the term system on a chip (SoC) is often used, although there's no exact delineation in terms of RAM, clock speed and so on.
The embedded market was estimated to be in excess of $140 billion in 2013, with many analysts projecting a market larger than $20 billion by 2020. Manufacturers of chips for embedded systems include many mainstays of the computer world, such as Apple, IBM, Intel and Texas Instruments, as well as numerous other companies less familiar to those outside the field. Arm has been a highly influential vendor in this space. The company began as an outgrowth of Acorn, a U.K. maker of early PCs. Arm chips, produced under license by other companies, are based on the reduced instruction set computer ( RISC ) architecture and are often used in mobile phones; they remain the most widely deployed SoC in the embedded world, with billions of units fielded.
Embedded system software
A typical industrial microcontroller is unsophisticated compared to the typical enterprise desktop computer and generally depends on a simpler, less-memory-intensive program environment. The simplest devices run on  bare metal  and are programmed directly using the chip CPU's machine code language.
Often, embedded systems use operating systems or language platforms tailored to embedded use, particularly where real-time operating environments must be served. At higher levels of chip capability, such as those found in SoCs, designers have increasingly decided the systems are generally fast enough and the tasks tolerant of slight variations in reaction time that near-real-time approaches are suitable. In these instances, stripped-down versions of the Linux operating system are commonly deployed, although other operating systems have been pared down to run on embedded systems, including  Embedded Java and Windows IoT (formerly  Windows Embedded ).
Generally, storage of programs and operating systems on embedded devices make use of either flash or rewritable flash memory.
Embedded firmware
The firmware on embedded systems, referred to as  embedded firmware , is specific software written into the memory of a device that serves the purpose of ROM, but can be updated more easily. Firmware can be stored in non-volatile memory devices including ROM,  programmable ROM ,  erasable PROM  or flash memory. Embedded firmware is used to control various device and system functions, for example, telling the device how to communicate with other devices, perform specific functions and provide input and output functionality.
The delineation between the terms embedded firmware and embedded software are blurring, but embedded software often refers to the only code running on a piece of hardware, while firmware can also refer to the chip that houses a device's basic input/output system ( BIOS ) or Unified Extensible Firmware Interface ( UEFI ), which connect software and a system's operating system.
Embedded systems vs. VLSI
Very-large-scale integration, or  VLSI , is a term that describes the complexity of an integrated circuit. VLSI is the process of embedding hundreds of thousands of transistors into a chip, whereas LSI (large-scale integration) microchips contain thousands of transistors, MSI (medium-scale integration) contain hundreds of transistors, and SSI (small-scale integration) contain tens of transistors. ULSI, or ultra-large-scale integration, refers to placing millions of transistors on a chip.
VLSI circuits are common features of embedded systems. Many ICs in embedded systems are VLSI, and the use of the VLSI acronym has largely fallen out of favor.
Debugging embedded systems
One area where embedded systems part ways with the operating systems and development environments of other, larger-scale computers is in the area of  debugging . While programmers working with desktop computer environments have systems that can run both the code being developed and separate debugger applications that monitor the actions of the development code as it is executed, embedded system programmers generally cannot.
Some programming languages run on microcontrollers with enough efficiency that rudimentary interactive debugging is available directly on the chip. Additionally, processors often have CPU debuggers that can be controlled -- and, thus, control program execution -- via a JTAG or similar debugging port.
In many instances, however, programmers of embedded systems need tools that attach a separate debugging system to the target system via a serial or other port. In this scenario, the programmer can see the source code on the screen of a conventional personal computer just as would be the case in the debugging of software on a desktop computer. A separate, frequently used approach is to run software on a PC that emulates the physical chip in software, thus making it possible to debug the performance of the software as if it were running on an actual, physical chip.
Broadly speaking, embedded systems have received more attention to testing and debugging because a great number of devices using embedded controls are designed for use in situations where safety and reliability are top priorities.
The internet of things builds on an embedded systems base
While some embedded systems can be relatively simple, a growing number either supplant human decision-making or offer capabilities beyond what a human could provide. For instance, some aviation systems, including those used in  drones , are able to integrate  sensor data  and act upon that information faster than a human could, permitting new kinds of operating features.
The embedded system is expected to continue rapidly growing, driven in large part by the internet of things (IoT). Expanding IoT applications such as wearables, drones,  smart homes , smart buildings, video surveillance,  3D printers  and smart transportation are expected to add to fuel embedded system growth.
Open Handset Alliance and Android:
The Open Handset Alliance (OHA) is a business alliance that was created for the purpose of developing open mobile device standards. The OHA has approximately 80 member companies, including HTC, Dell, Intel, Motorola, Qualcomm and Google. The OHA's main product is the Android platform - the world's most popular smartphone platform.
OHA members are primarily mobile operators, handset manufacturers, software development firms, semiconductor companies and commercialization companies. Members share a commitment to expanding the commercial viability of open platform development. OHA member companies back the open platform concept for a number of reasons, as follows:
· Lower overall handset costs: Opens up resources, which facilitates the focus on creating innovative applications, solutions and services.
· Developer-friendly environment: In the open-source community, developers share notes to expedite application development.
· Post-development: Provides an ideal channel for application marketing and distribution.
Introduction to Android:
Android is a Linux based operating system it is designed primarily for touch screen mobile devices such as smart phones and tablet computers. The operating system have developed a lot in last 15 years starting from black and white phones to recent smart phones or mini computers. One of the most widely used mobile OS   these days is android.  The android is software that was founded in Palo Alto of California in 2003.
The android is a powerful operating system and it supports large number of applications in Smartphones. These applications are more comfortable and advanced for the users. The hardware that supports android software is based on ARM architecture platform. The android is an open source operating system means that it’s free and any one can use it. The android has got millions of apps available that can help you managing your life one or other way and it is available low cost in market at that reasons android is very popular.
Android Architecture:
Linux kernel:
The android uses the powerful Linux kernel and it supports wide range of hardware drivers. The kernel is the heart of the operating system that manages input and output requests from software. This provides basic system functionalities like process management, memory management, device management like camera, keypad, display etc the kernel handles all the things. The Linux is really good at networking and it is not necessary to interface it to the peripheral hardware. The kernel itself does not interact directly with the user but rather interacts with the shell and other programs as well as with the hard ware devices on the system.
Libraries:
The on top of a Linux kennel there is a set of libraries including open source web browser such as webkit, library libc. These libraries are used to play and record audio and video. The SQLite is a data base which is useful for storage and sharing of application data. The SSL libraries are responsible for internet security etc.
Android Runtime:
X
The android runtime provides a key component called Dalvik Virtual Machine which is a kind of java virtual machine. It is specially designed and optimized for android. The Dalvik VM is the process virtual machine in the android operating system. It is a software that runs apps on android devices.
The Dalvik VM makes use of Linux core features like memory management and multithreading which is in a java language. The Dalvik VM enables every android application to run it own process. The Dalvik VM  executes the files in the .dex format.
Application frame work:
The application frame work layer provides many higher level services to applications such as windows manager, view system, package manager, resource manager etc. The application developers are allowed to make use of these services in their application.
Applications and Features:
You will find all  the android applications  at the top layer and you will write your application and install on this layer. Example of such applications are contacts, books, browsers, services etc. Each application perform a different role in the over all applications.
Features:
· Connectivity: GSM/EDGE, IDEN, CDMA, Bluetooth, WI-FI, EDGE,3G,NFC, LTE,GPS.
· Messaging: SMS, MMS, C2DM (could to device messaging), GCM (Google could messaging)
· Multilanguage support
· Multi touch
· Video calling
· Screen capture
· External storage
Downloading and installing eclipse:
The list of software required to setup android for eclipse IDE manually.
1. Install the JDK
2. Download and install the Eclipse for developing android application
3. Download and Install the android SDK
4. Intall the ADT plugin for eclipse
5. Configure the ADT plugin
6. Create the AVD
1. Start Android Studio.
2. To open SDK Manager, do any of the these: On Android Studio landing page, select Configure > SDK Manager. ...
3. In the Default Settings dialog box, click these tabs to install Android SDKplatform packages and developer tools. SDK Platforms: Select the latest Android SDK package. ...
4. Click Apply.
5. Click OK.
Exploring the Android SDK
Both tools are accessible through the graphical interface of Google's own Android development environment, Android Studio, as shown in Figure 1 or through the command line. If you are not familiar with it, you can check out the reference section at the end of this article or our previous tutorial, " Using Android Studio ". The goal of this tutorial is to at least point out the most common usage popular among developers and explain some different options.
Figure 1: Tools on Android Studio
Managing Packages from the SDK Manager
You can start SDK Manager from Android Studio's menu by choosing "Tools -> Android -> SDK Manager" or by clicking the toolbar icon. You should see the main dialog, as shown in Figure 2. The first thing you can verify is whether the SDK location is indeed correct. In my case, it is under "C:\android-root\sdk\" as shown. There are three tabs below that allow you to choose your installation options from Platforms, Tools, or Update Sites. Furthermore, there is a checkbox for "Show Package Details" on the lower right corner; I strongly recommend that you enable it as well. That way, you clearly can see what packages are actually installed on the machine.
Some of the system images take up several gigabytes of your storage space, but you probably will never have a need to use some of them. For example, you perhaps will not do apps for TV or smart watches, so you can feel free to uncheck those system images. And, if you are specific about apps targeting at specific CPU types—for example ARM—you can remove those Intel 32-bit or 64-bit system images. If you plan to work only on apps for the most recent devices with newer API levels, say Android 7.0 Nougat or later, any APIs before that version can be unchecked. Checkboxes on the items can be used to install, uninstall, or update. Once you confirm your selections and click the "Apply" button, the component installer will start as in Figure 3, responding to your request.
Figure 2: SDK Manager
Using SDK Manager from the Command Line
Although it is convenient and simple enough to interact with the SDK Manager through a graphical interface, we still sometimes need to accomplish similar goals in a programmatic mode; for example, keeping a target platform up to date for a specific device in a fully-automated setup. To locate the executable, we first go to the Android SDK installed root folder. In my case, it is at "c:\android-root\sdk\". From there, continue to look under the subfolder "tools\bin\". We can test the command "sdkmanager --list" to take an inventory of what packages are currently installed on the machine and what are available from the remote server, as in Figure 4. To install available packages, you specify the quoted names separated by spaces and provide each of their folder names separated by semicolons, as in the following code example. It tries to install the platforms for both API levels 21 and 24. Similarly, the "--uninstall" and "--update" options follow the same rules.
sdkmanager "platforms;android-21" "platforms;android-24"
What is the Android SDK:
The Android SDK (software development kit) is a set of development tools used to develop applications for Android platform. The Android SDK includes the following:
· Required libraries
· Sample source code
· Tutorials for the Android OS
· Every time Google releases a new version of Android, a corresponding SDK is also released. To be able to write programs with the latest features, developers must download and install each version’s SDK for the particular phone.
· The development platforms that are compatible with SDK include operating systems like Windows (XP or later), Linux (any recent Linux distribution) and Mac OS X (10.4.9 or later). The components of Android SDK can be downloaded separately. Third party add-ons are also available for download.
· Although the SDK can be used to write Android programs in the command prompt, the most common method is by using an integrated development environment (IDE). The recommended IDE is Eclipse with the Android Development Tools (ADT) plug-in. However, other IDEs, such as NetBeans or IntelliJ, will also work. Most of these IDEs provide a graphical interface enabling developers to perform development tasks faster. Since Android applications are written in Java code, a user should have the Java Development Kit (JDK) installed.
Overview of Android Lifecycles:
A general overview of the lifecycle of an application is shown in the following figure, which is taken from the documentation for  Activity .
Application : Hello world
Creating your first Android
The first step is to create a simple Android Application using Android studio. When you click on Android studio icon, it will show screen as shown below
You can start your application development by calling start a new android studio project. in a new installation frame should ask Application name, package information and location of the project.−
After entered application name, it going to be called select the form factors your application runs on, here need to specify Minimum SDK, in our tutorial, I have declared as API23: Android 6.0(Mashmallow) −
The next level of installation should contain selecting the activity to mobile, it specifies the default layout for Applications.
At the final stage it going to be open development tool to write the application code.
Anatomy of Android Application
Before you run your app, you should be aware of a few directories and files in the Android project −
The Main Activity File
The main activity code is a Java file MainActivity.java. This is the actual application file which ultimately gets converted to a Dalvik executable and runs your application. Following is the default code generated by the application wizard for Hello World! application −
package com.example.helloworld;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
@Override
}
}
Here, R.layout.activity_main refers to the activity_main.xml file located in the res/layout folder. The onCreate() method is one of many methods that are figured when an activity is loaded.
The Manifest File
Whatever component you develop as a part of your application, you must declare all its components in a manifest.xml which resides at the root of the application project directory. This file works as an interface between Android OS and your application, so if you do not declare your component in this file, then it will not be considered by the OS. For example, a default manifest file will look like as following file −
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
Here <application>...</application> tags enclosed the components related to the application. Attribute android:icon will point to the application icon available under res/drawable-hdpi. The application uses the image named ic_launcher.png located in the drawable folders
The <activity> tag is used to specify an activity and android:name attribute specifies the fully qualified class name of the Activity subclass and the android:label attributes specifies a string to use as the label for the activity. You can specify multiple activities using <activity> tags.
The action for the intent filter is named android.intent.action.MAIN to indicate that this activity serves as the entry point for the application. The categoryfor the intent-filter is named android.intent.category.LAUNCHER to indicate that the application can be launched from the device's launcher icon.
The @string refers to the strings.xml file explained below. Hence, @string/app_name refers to the app_name string defined in the strings.xml file, which is "HelloWorld". Similar way, other strings get populated in the application.
Following is the list of tags which you will use in your manifest file to specify different Android application components −
· <activity>elements for activities
· <service> elements for services
The Strings File
The strings.xml file is located in the res/values folder and it contains all the text that your application uses. For example, the names of buttons, labels, default text, and similar types of strings go into this file. This file is responsible for their textual content. For example, a default strings file will look like as following file −
<resources>
</resources>
The Layout File
The activity_main.xml is a layout file available in res/layout directory, that is referenced by your application when building its interface. You will modify this file very frequently to change the layout of your application. For your "Hello World!" application, this file will have following content related to default layout −
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
</RelativeLayout>
This is an example of simple RelativeLayout which we will study in a separate chapter. The TextView is an Android control used to build the GUI and it have various attributes like android:layout_width, android:layout_height etc which are being used to set its width and height etc.. The @string refers to the strings.xml file located in the res/values folder. Hence, @string/hello_world refers to the hello string defined in the strings.xml file, which is "Hello World!".
Running the Application
Let's try to run our Hello World! application we just created. I assume you had created your AVD while doing environment set-up. To run the app from Android studio, open one of your project's activity files and click Run