Android Operative system functional overview for developers

1. Android

2. Overview
• Android is an open source platform designed for
mobile devices. Android is founded in the year 2003
by Andy Rubin,Rich miner,Nick sears and Chris
white and names it as “Android Inc” .
 Then the company is acquired by Google and now it
is aligned with “open Handset Alliance” .
 First Android mobile is G1 Phone manufactured by
HTC and sold by wireless carrier T-mobile USA.

3. Android Versions:
Versions Nick Name
Android 1.0 NA
Android 1.1 NA
Android 1.5 Cup Cake
Android 1.6 DoNut
Android 2.0 Eclair
Android 2.2 Froyo
Android 2.3 GingerBread
Android 3.0 HoneyComb
Android 4.0 IceCream Sandwich

4. Android Stack

5. Android Stack overview :
 Android is built in the top of LINUX operating system.
 Other Libraries are
 Web-kit (Web rendering engine)
 SqlLite (Sql DataBase)
 OpenGL (3D graphics Library)
 OpenSSL (Secured Socket Layer)

6. Dalvik Architecture
• Dalvik is an virtual machine designed specifically for
Android by Dan Bornstein from Google.
Reasons for replacing Java VM :
 Dalvik focus strictly on mobile devices one of these
are battery power consumptions and other is
processing power
 Though Java Language,Java tools and Java libraries
are open source , Java VM is not . To make it license
friendly Android introduces Dalvik VM.
 Dalvik VM is closest to Java libraries but removes
interface (awt and swing).

7. How it works ?
 In Java , we write Java source code and compile to
Java byte code using Java compiler , then byte code
is run on Virtual machine.
 In Android , we write Java code and still convert byte
code using Java compiler and recompiled again with
Dalvik virtual machine.

9. Activity Life-cycle
 Introduction : An activity is a single screen that user
sees on the screen.
 Launching an activity is an expensive , it creates a
new Linux process and allocates memory for the UI
objects and loads the XML layout .To do load an
activity it takes lot of task , if user switches the screen
to persist the activity state Android introduces Activity
manager.

10. Activity LifeCycle

11. Activity State's :
 Start state (Activity doesn't exist in memory and starts
loading it )
 Running state (user Interaction state)
 Paused state (App is visible but not used )
 Stopped state.(App is invisible and still exist in the
memory)
 Destroy state. (App removed from the memory)

12. Intent
 Intents are messages that are sent among major
building blocks. They trigger an activity to start up, a
service to start or stop, or are simply broadcasts.
Intents are asynchronous, meaning the code that is
sending them doesn’t have to wait for them to be
completed.
 Intent can be explicit or implicit command.

13. Intent Diagram

14. Content Providers
 Content Providers are interfaces for sharing data
between applications. Android by default runs each
application in its own sandbox so that all data that
belongs to an application is totally isolated from other
applications on the system. While small amounts of
data can be passed between applications via Intents

15. Content Providers

16. Android User Interface
• Android UI :
 Declarative Approach (XML based Layout).
 Programmatic Approach (Java Code To
develop the UI)