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Android OS

Android OS. Google's Mobile Device Operating 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.

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Android OS

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  1. Android OS Google's Mobile Device Operating System

  2. Intro & Overview Steve Mance

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

  4. Intro/Overview - What is Android? • Operating System optimized for Mobile Devices • Open Source • Maintained by Google • Based on the Linux kernel

  5. Intro/Overview - System Overview

  6. Intro/Overview - History • Android Inc. founded 2003 •  Purchased by Google from initial dveloper in 2005 •  Version 2.0 released 2009 •  Starts to take hold in the Smartphone Market • Version 3.0 released 2011 • Predominantly used in Tablets

  7. Intro/Overview - Features • Apps • The "Programs" of Android • Composed of application components • Widgets • Provide information and tools directly on the Home Screen • No need to launch an activity • Marketplace • A place for App distribution, run by Google • Developers can sell their apps or give them away freely • Third Party distributors also available

  8. Intro/Overview - Marketshare

  9. 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)

  10. Intro/Overview - Relevant Devices Tablets: Motorola Xoom Samsung Galaxy Tab 4G Dell Streak Asus Eee-Pad Transformer +More Phones: HTC Thunderbolt Motorola Droid/2/X HTC Evo Samsung Nexus S +Many More

  11. Hardware and I/O Dmitiry Lozovatskiy

  12. 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.

  13. Kernel Geoff Hetherington

  14. 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

  15. 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

  16. 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

  17. Binder • A tool for inter-process communication • Binder driver manages synchronization between processes • Facilitated using different states • Receive blocked • Ready • Send blocked • Reply blocked

  18. 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()

  19. 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

  20. 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

  21. 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

  22. Software Architecture Raanan Korinow

  23. System Libraries • libc for C and C++ • Why not glibc? • libpthread • not 100% POSIX compliant • Isn't Android programmed in Java? • SDK vs NDK

  24. More Libraries • SSL • SQLite • WebKit (and LibWebCore for embeddable webpages) •  Audio Manager • Media Framework • MediaPlayer

  25. Graphics Libraries • Scalable Graphics Library (SGL- for 2D) • OpenGL for Embedded Devices (for 3D) •  FreeType (vector and bitmap fonts) •  Surface Manager • Composes 2D and 3D windows, widgets, apps, toolbars and more using Surface Flinger • Uses Binder IPC to get buffers from apps to put into frames

  26. 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

  27. 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

  28. Reboot Bug (2008) Android allowed a remote device to be controlled over serial port If 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.

  29. Programming on Android Jin Kim

  30. 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

  31. 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)

  32. 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 • 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 

  33. Steps for Developing Applications  6. Debug your application with the SDK debugging tools • Involves using a JDWP-compliant debugger along with the tools provided with Android SDK.  7. Test your application with the Testing and Instrumentation             framework • The Android SDK provides a testing and instrumentation framework to help set up and run tests

  34. Support for Additional Languages • In 2009, Google announced the Android Native Development Kit (NDK) • Allows developers to build Android software components with C and C++ • Comes with limitations, however • 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

  35. 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

  36. Application Components Jason Loewy

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

  38. • 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 - Activity

  39. • 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 - Services

  40. • 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 - Content Provider

  41. • 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. Component - Broadcast Receiver

  42. Android's Future Adam LaFave

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

  44. Reasons for Growth • Open Source • Many handset / tablet makers utilize this free OS (HTC, Motorola, Samsung) • Saturates the market with Android hardware on multiple carriers • Free to develop on -- no overhead charge for developing apps (iOS) • Strong fan base • Alternative to iOS-based devices • It's Google

  45. 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

  46. Mobile Growth Visualized

  47. Merger With Chrome OS Eric Schmidt (ex-CEO): • The two efforts [Android and Chrome OS] will ultimately converge. • "We're working overtime to get these technologies merged in the right way." What does this mean for Android?

  48. Merger With Chrome OS Chrome OS heavily utilizes the cloud. • 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. • Pictures, songs, videos, etc. may not need to be stored on the devices themselves -- instead pulled from the cloud when requested.

  49. References and Resources http://elinux.org/Android_Kernel_Features http://cs736-android.pbworks.com/w/page/5834465/ASHMEM http://elinux.org/Android_Logging_System http://developer.android.com/index.html http://developer.android.com/resources/articles/painless-threading.html http://android-developers.blogspot.com/2010/04/multitasking-android-way.html http://www.kroah.com/log/linux/android-kernel-problems.html http://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=1622614 http://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.html http://arstechnica.com/open-source/news/2009/06/android-goes-beyond-java-gains-native-cc-dev-kit.ars http://www.informationweek.com/news/internet/google/218700186

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