Android is an open source operating system used for mobile devices like smartphones and tablets. It was developed by the Open Handset Alliance led by Google. Android allows developers to create applications that run on multiple devices by developing for the Android platform. The first commercial version of Android was released in 2008. Key features of Android include a beautiful user interface, connectivity, storage, media support, messaging, web browsing, and multi-touch capabilities. Applications are usually developed in Java using the Android SDK and can be distributed through app stores.

1. Introduction to 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.
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2. Application Development
• 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.
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3. First Version of 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.
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4. Why Android?
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5. Features of Android
Sr.No. Feature & Description
1 Beautiful UI
Android OS basic screen provides a beautiful and intuitive user interface.
2 Connectivity
GSM/EDGE, IDEN, CDMA, EV-DO, UMTS, Bluetooth, Wi-Fi, LTE, NFC and WiMAX.
3 Storage
SQLite, a lightweight relational database, is used for data storage purposes.
4 Media support
H.263, H.264, MPEG-4 SP, AMR, AMR-WB, AAC, HE-AAC, AAC 5.1, MP3, MIDI, Ogg
Vorbis, WAV, JPEG, PNG, GIF, and BMP.
5 Messaging
SMS and MMS
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6. Features of Android
6 Web browser
Based on the open-source WebKit layout engine, coupled with Chrome's V8 JavaScript engine
supporting HTML5 and CSS3.
7 Multi-touch
Android has native support for multi-touch which was initially made available in handsets such as
the HTC Hero.
8 Multi-tasking
User can jump from one task to another and same time various application can run
simultaneously.
9 Resizable widgets
Widgets are resizable, so users can expand them to show more content or shrink them to save
space.
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7. Features of Android
10 Multi-Language
Supports single direction and bi-directional text.
11 GCM
Google Cloud Messaging (GCM) is a service that lets developers send short message data to their users
on Android devices, without needing a proprietary sync solution.
12 Wi-Fi Direct
A technology that lets apps discover and pair directly, over a high-bandwidth peer-to-peer connection.
13 Android Beam
A popular NFC-based technology that lets users instantly share, just by touching two NFC-enabled
phones together.
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8. Android Applications
• Android applications are usually developed in the Java language
using the Android Software Development Kit.
• Once developed, Android applications can be packaged easily
and sold out either through a store such as Google
Play, SlideME, Opera Mobile Store, Mobango, F-droid and
the Amazon Appstore.
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9. Power of Android
• Android powers hundreds of millions of mobile devices in more
than 190 countries around the world. It's the largest installed
base of any mobile platform and growing fast. Every day more
than 1 million new Android devices are activated worldwide.
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10. Categories of Android applications
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11. Android Versions
• The code names of android ranges from A to N currently, such
as Aestro, Blender, Cupcake, Donut, Eclair, Froyo, Gingerbread,
Honeycomb, Ice Cream Sandwitch, Jelly Bean, KitKat, Lollipop
and Marshmallow.
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12. What is API level?
• API Level is an integer value that uniquely identifies the framework
API revision offered by a version of the Android platform.
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13. Android - Architecture
• Android operating system is a stack of software components
which is roughly divided into five sections and four main layers
as shown below in the architecture diagram.
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14. Android - Architecture
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15. Linux kernel
• At the bottom of the layers is Linux Kernel and is heart of the
android architecture
• This provides a level of abstraction between the device hardware
and the other components of android architecture
• It contains all the essential hardware drivers like camera, keypad,
display, Bluetooth, audio, etc.
• It helps to get the work done from Hardware E.g Camera, Keypad
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16. Divided into three parts
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17. The features of Linux kernel are
• Security: The Linux kernel handles the security between the
application and the system.
• Memory Management: It efficiently handles the memory
management thereby providing the freedom to develop our apps.
• Process Management: It manages the process well, allocates
resources to processes whenever they need them.
• Network Stack: It effectively handles the network communication.
• Driver Model: It ensures that the application works properly on the
device and hardware manufacturers responsible for building their
drivers into the Linux build.
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18. Libraries
• On top of Linux kernel there is a set of libraries such as Media,
Graphics, Surface Manager, OpenGL etc. to provide a support
for android development. including open-source Web browser
engine WebKit, well known library libc, SQLite database libraries
to play and record audio and video, SSL libraries responsible for
Internet security etc. which is a useful repository for storage and
sharing of application data.
• It provide logical instructions to Linux Kernel
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19. Android Libraries
• android.app − Provides access to the application model and is
the cornerstone of all Android applications.
• android.content − Facilitates content access, publishing and
messaging between applications and application components.
• android.database − Used to access data published by content
providers and includes SQLite database management classes.
• android.opengl − A Java interface to the OpenGL ES 3D
graphics rendering API.
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20. Android Libraries
• android.os − Provides applications with access to standard
operating system services including messages, system services and
inter-process communication.
• android.text − Used to render and manipulate text on a device
display.
• android.view − The fundamental building blocks of application user
interfaces.
• android.widget − A rich collection of pre-built user interface
components such as buttons, labels, list views, layout managers,
radio buttons etc.
• android.webkit − A set of classes intended to allow web-browsing
capabilities to be built into applications.
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21. Android Runtime
• This section provides a key component called Dalvik Virtual
Machine which is a kind of Java Virtual Machine specially
designed and optimized for Android.
• The Dalvik VM makes use of Linux core features like memory
management and multi-threading, which is intrinsic in the Java
language. The Dalvik VM enables every Android application to
run in its own process, with its own instance of the Dalvik virtual
machine.
• Android Run time= Core Libraries + DVM
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22. Application runtime –
• Android Runtime environment is one of the most important part
of Android. It contains components like core libraries and the
Dalvik virtual machine(DVM). Mainly, it provides the base for the
application framework and powers our application with the help
of the core libraries.
• Like Java Virtual Machine (JVM), Dalvik Virtual Machine
(DVM) is a register-based virtual machine and specially
designed and optimized for android to ensure that a device can
run multiple instances efficiently.
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23. Application framework –
• Application Framework provides several important classes which
are used to create an Android application.
• It provides a generic abstraction for hardware access and also
helps in managing the user interface with application resources.
• Generally, it provides the services with the help of which we can
create a particular class and make that class helpful for the
Applications creation.
• It includes different types of services activity manager, notification
manager, view system, package manager etc. which are helpful
for the development of our application according to the
requirements.
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24. Applications –
• Applications is the top layer of android architecture. The pre-
installed applications like home, contacts, camera, gallery etc
and third party applications downloaded from the play store like
chat applications, games etc. will be installed on this layer only.
• It runs within the Android run time with the help of the classes
and services provided by the application framework.
• At the top is the User Developed Applications
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25. Android Runtime
• The Android runtime also provides a set of core libraries which
enable Android application developers to write Android
applications using standard Java programming language.
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26. Android - Application Components
• Application components are the essential building blocks of an
Android application. These components are loosely coupled by
the application manifest file AndroidManifest.xml that describes
each component of the application and how they interact.
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27. Components of Android application
Sr.No. Components & Description
1
Activities
They dictate the UI and handle the user interaction to the smart phone
screen.
2
Services
They handle background processing associated with an application.
3
Broadcast Receivers
They handle communication between Android OS and applications.
4
Content Providers
They handle data and database management issues.
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28. Activities
• An activity represents a single screen with a user interface, in-
short Activity performs actions on the screen.
• For example, an email application might have one activity that
shows a list of new emails, another activity to compose an email,
and another activity for reading emails. If an application has
more than one activity, then one of them should be marked as
the activity that is presented when the application is launched.
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29. Activity in Android
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• An activity represents a single screen with a user interface just like
window or frame of Java
• Android system initiates its program with in an Activity starting
with a call on onCreate() callback method.
 There is a sequence of callback methods that start up an activity
and a sequence of callback methods that tear down an activity

30. Activity Life Cycle
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31. • The Activity class defines the following call backs i.e. events. You
don't need to implement all the callbacks methods
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32. Activity Life Cycle
Sr.No Callback & Description
1
onCreate()
This is the first callback and called when the activity is first created.
2
onStart()
This callback is called when the activity becomes visible to the user.
3
onResume()
This is called when the user starts interacting with the application.
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33. Activity Life Cycle
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4
onPause()
The paused activity does not receive user input and cannot execute any code and called when the current activity
is being paused and the previous activity is being resumed.
5
onStop()
This callback is called when the activity is no longer visible.
6
onDestroy()
This callback is called before the activity is destroyed by the system.
7
onRestart()
This callback is called when the activity restarts after stopping it.

34. An activity is implemented as a subclass of Activity
class as follows −
public class MainActivity extends Activity {
}
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