Android OS

Google's Mobile DeviceOperating System

Intro & Overview

Steve Mance

Agenda

• Intro/Overview• Hardware and IO• Kernel• Software Architecture• Programming Languages• Application Framework and Components• Future for mobile and non-mobile platforms

Intro/Overview - What is Android?

• Operating System optimized for Mobile Devices

• Open Source

• Maintained by Google

• Based on the Linux kernel

Intro/Overview - System Overview

Intro/Overview - History

• Android Inc. founded 2003

•  Purchased by Google from initial dveloper in 2005

•  Version 2.0 released 2009o  Starts to take hold in the Smartphone Market

 • Version 3.0 released 2011

o Predominantly used in Tablets

Intro/Overview - Features

• Appso The "Programs" of Androido Composed of application components

• Widgetso Provide information and tools directly on the Home

Screeno No need to launch an activity

• Marketplaceo A place for App distribution, run by Googleo Developers can sell their apps or give them away freelyo Third Party distributors also available

Intro/Overview - Marketshare

Intro/Overview - Marketshare

• Late 2009/Early 2010 Android begins it's growth in the US Smartphone market

•  As of Janurary 2011 the Android OS has the highest marketshare in smartphones in the US

• Now more prevalent than iOS (Apple) and Blackberry (RIM)

Intro/Overview - Relevant Devices

Phones:HTC Thunderbolt Motorola Droid/2/XHTC EvoSamsung Nexus S+Many More

Tablets:Motorola XoomSamsung Galaxy Tab 4GDell StreakAsus Eee-Pad Transformer+More

Hardware and I/O

Dmitiry Lozovatskiy

Device Requirements

Chipset:    ARM-based (32-bit Advanced reduced instruction set computer architecture machine). Dalvik VM graphics processing, currently assume an ARM architecture.

Memory:    128 MB RAM; 256 MB Flash External.  Android can boot and run in     configurations with less memory, but it isn't recommended.

Storage:    Mini or Micro SD. Not necessary for basic bring up, but recommended.

Primary Display:    QVGA (320×240) TFT LCD or larger, 16-bit color or better.Touch screen interface no smaller than 2.8 inches in size.

Navigation Keys:    5-way navigation with 5 application keys, power, camera and  volume controls.

Camera:    Must have a resolution of at least 2 megapixels, but not required.

USB:     Standard mini-B USB . For flashing the device system images and debugging.

Bluetooth:     1.2 or 2.0, but not required.

Kernel

Geoff Hetherington

About the Android Kernel

• Derived from the Linux 2.6 kernel, with added enhancements not found in Linux

• Kernel mode and user mode are used the same as in the Linux kernel

Ashmem

• Anonymous Shared Memory

• Ashmem uses virtual memory

• The kernel is allowed to free this shared memory

• More viable for low memory devices, because it can discard shared memory units

Pmem

• Process memory allocator

• Similar to ashmem, but uses physically contiguous memory as opposed to virtual memory

• Manages large, contiguous regions of memory shared between user space and the kernel drivers

Binder

• A tool for inter-process communication

• Binder driver manages synchronization between processes

• Facilitated using different stateso Receive blockedo Readyo Send blockedo Reply blocked

Logger

• System logging, separate from the Linux kernel’s own logging system

• Stores logs from applications, events, and the system

• Write path is optimized to avoid overhead from open(), write(), and close()

Android Power Management

• Wake locks are used to hold the machine awake until a wake lock is released

• Wake locks issued in user space, handled by kernel

• Power management can shut CPU down if there are no active wake locks

Multithreading and Multitasking

• Expensive operations are done in a background service

• Slow work is done in a background thread

• Ensure the UI is responsive to the user

• Processes are not killed when the user closes an application, instead they remain in the background

Removal From Linux Kernel

• Android code removed from Linux kernel as of December, 2009

• Kernel development has been removed from the Linux kernel tree

• Android kernel includes features that would need to be integrated into Linux kernel to merge it into main kernel tree

Software Architecture

Raanan Korinow

System Libraries

• libc for C and C++o Why not glibc?

• libpthreado not 100% POSIX compliant

• Isn't Android programmed in Java?

• SDK vs NDK

More Libraries

• SSL

• SQLite

• WebKit (and LibWebCore for embeddable webpages)

•  Audio Manager

• Media Frameworko MediaPlayer

Graphics Libraries

• Scalable Graphics Library (SGL- for 2D)

• OpenGL for Embedded Devices (for 3D)

•  FreeType (vector and bitmap fonts)

•  Surface Managero Composes 2D and 3D windows, widgets, apps, toolbars

and more using Surface Flingero Uses Binder IPC to get buffers from apps to put into

frames

Hardware Abstraction Libraries

• GPS, Radio, Camera, Bluetooth, other I/O

• Hardware drivers must implement in order for applicationss to use them

• Applications interact with the abstraction libraries, not the driver

• Promotes variety in hardware without breaking applications

• Gives OS tighter control over devices

Android vs Linux Software Architecture

• No native window library

• Does not support full set of GNU libraries

• Difficult to port Linux applications to Android, but possible if working within libc constraints

Reboot Bug (2008)

Android allowed a remote device to be controlled over serial portIf device not attached, phone would execute ALL text input as shell commands

Typing “reboot” in an email/browser/anywhere would result in phone rebooting

Architecture and Components at fault! Promptly fixed, but jeopardized Android’s reputation.

Programming on Android

Jin Kim

Application Development  

• Most Android applications written in Java  • However, no Java Virtual Machine in the platform  

 • Java classes compiled into Dalvik virtual machine

 • Dalvik - a specialized virtual machine designed specifically

for Android

Android Software Development Kit (SDK)• The SDK includes a comprehensive set of development

tools. • Includes a debugger, libraries, documentation, sample code

 • These tools are accessed through an Eclipse plugin called

ADT (Android Development Tools) or from command line • Developing with Eclipse is preferred (but not required)

Steps for Developing Applications

 1. Install Eclipse or own IDE  2. Install ADT plugin, or an editor of your choice  3. Set up Android Virtual Devices or hardware devices on which you will install your applications  4. Create an Android project

o Contains all source code and resource files for your application. Built into an .apk package that you can install on Android devices. 

  5. Build and run your application 

Steps for Developing Applications

 6. Debug your application with the SDK debugging toolso Involves using a JDWP-compliant debugger along with

the tools provided with Android SDK.  7. Test your application with the Testing and Instrumentation             framework

o The Android SDK provides a testing and instrumentation framework to help set up and run tests

Support for Additional Languages

• In 2009, Google announced the Android Native Development Kit (NDK)o Allows developers to build Android software components

with C and C++ 

o Comes with limitations, however 

o Intended to be used alongside Java to code individual parts of programs, not as a full alternative

 • Google also launched the Android Scripting Environment

(ASE) - allows developers to build apps with Python and Lua

New Language

• July, 2009, Google released language called Simple, designed specifically for Android apps

 • Simple - based on BASIC

 • Easy to learn and use language

 • Gives both amateur and professional programmers  a quick

and easy way to write Android apps

Application Components

Jason Loewy

Android Components

• Four types: Activities -     Services - Content     Providers - Broadcast   Receivers • Part of the building blocks   of applications• Each component type   performs its own unique   action

 

Component - Activity

• Activities can be thought of   as a single view that   provides a user interface

• Each activity is it's own   entity but all activities work   together to form the   application.

 

Component - Services

• Services are tasks that run  in the background • Run on the main process   thread unless otherwise   specified

• Examples include playing  music while using other  applications, handling   network transactions, etc

(Image from http://marakana.com)

Component - Content Provider

• Content Providers allow for   cross application  communication

• Applications must have   necessary permission levels  to communicate

• For example allows   applications to select an   image from the phones     library, select a contacts    info from the contacts list,   etc

 

Component - Broadcast Receiver

• Broadcast are system wide  notifications

• Broadcast Receivers allow  applications to receive those  notifications and act   accordingly

• For example releasing   allocation memory on a low   memory warning.

 

Android's Future

Adam LaFave

Growth

Android predicted to grow in market share:o  38.6% (#2) tablet OSes by 2015o  48.8% (#1) phone OSes by 2015

Reasons for Growth

• Open Sourceo Many handset / tablet makers utilize this free OS (HTC,

Motorola, Samsung) Saturates the market with Android hardware on

multiple carrierso Free to develop on -- no overhead charge for developing

apps (iOS)

• Strong fan base

• Alternative to iOS-based devices

• It's Google

With Great Growth Comes Great Responsibility

Fragmentation• Different screen sizes, hardware features, user interfaces

and carrier-decided OS updates cause inconsistent Android experience

• After selling a device, manufacturer has little incentive to offer updates

Security• More users = more attractive to malware writers• "Open" market means it's customer's responsibility to stay

away from malicious software• Smartphone use in business world poses risk

Mobile Growth Visualized

Merger With Chrome OS

Eric Schmidt (ex-CEO):o The two efforts [Android and Chrome OS] will ultimately

converge.o "We're working overtime to get these technologies merged in

the right way."

What does this mean for Android?

Merger With Chrome OS

Chrome OS heavily utilizes the cloud.o A small hard drive is only needed for the OS itself.

The merger may bring more cloud services to Android, possibly eliminating the need for internal storage.

o Pictures, songs, videos, etc. may not need to be stored on the devices themselves -- instead pulled from the cloud when requested.

References and Resources

http://elinux.org/Android_Kernel_Featureshttp://cs736-android.pbworks.com/w/page/5834465/ASHMEMhttp://elinux.org/Android_Logging_Systemhttp://developer.android.com/index.htmlhttp://developer.android.com/resources/articles/painless-threading.htmlhttp://android-developers.blogspot.com/2010/04/multitasking-android-way.htmlhttp://www.kroah.com/log/linux/android-kernel-problems.htmlhttp://www.silicon.com/technology/software/2011/02/16/android-chrome-os-to-converge-says-googles-eric-schmidt-39746988/http://www.gartner.com/it/page.jsp?id=1626414http://www.gartner.com/it/page.jsp?id=1622614http://www.eweek.com/c/a/Mobile-and-Wireless/Androids-Surging-Popularity-10-Factors-Driving-Its-Growth-485860/http://www.pcworldme.net/2011/02/20/fragmentation-could-stunt-androids-growth/http://developer.android.com/guide/basics/what-is-android.htmlhttp://arstechnica.com/open-source/news/2009/06/android-goes-beyond-java-gains-native-cc-dev-kit.arshttp://www.informationweek.com/news/internet/google/218700186