Android OS
Kesav Kaliyaperumal
kesav.kaliyaperumal@gmail.com
Yummy Desserts!
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Cupcake
Donuts
Éclair
Frozen Yoghurt (Froyo)
Gingerbread
Honeycomb
What do these have in common?
Smartphone OS
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Symbian
Windows Mobile
RIM Blackberry OS
Apple iOS
Google Android
Palm WebOS
Windows Phone 7
Android OS
• Fastest growing mobile OS
• Over 300,000 Android activations a day
• Android overtook iOS as the dominant OS
in US during 2H 2010
• First phone launched HTC G1 in 2008
• Currently an OS of choice for Motorola,
HTC, Samsung, Sony Ericsson, among
others
• Software updates every few months
Android – what is it?
• software stack for mobile devices
– incl. OS, middleware and key applications
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Open source – source code is open and contributions are welcome
application framework enabling reuse/replacement of apps
Dalvik virtual machine optimized for mobile
integrated browser based on webkit
Optimized graphics – 2D graphics library, 3D based on OPEN GL
ES
SQLite for data storage
Media support (MPEG4, H.264, MP3, AAC, JPG, PNG,…)
Support for radio interfaces, Bluetooth, WiFi, Camera, GPS,
accelerometer
Software Development Kit (SDK)
Preinstalled applications from Google (GMS)
– Gmail, Maps, Search, Voice Search, Youtube
Software Stack
• Linux kernel
• Libraries
• Android run time
– core libraries
– Dalvik virtual machine
• application layer
• application protocol
Android Architecture
Android
• Google Maps and other GMS applications
• Background services and applications
– allows multi tasking of applications
• Shared Data and interprocess communication
• All applications are equal
– does not discriminate between native and non-native
applications
– allows any applications to be enhanced/reused
• p2p interdevice application messaging
Dalvik VM
• All applications written in Java and converted to
the dalvik executable .dex
• Every android app runs its own process, with its
own instance of the dalvik virtual machine
• Not a traditional JVM, but a custom VM
designed to run multiple instances efficiently on
a single device
• VM uses linux kernel to handle low-level
functionality incl. security, threading, process
and memory management
Application Framework
• Rich, extensible set of Views
– apps can inclused lists, grids, text boxes, buttons,
web browser
• Content Providers
– allows data access from other applications or share
own data
• Resource Manager
– access to localized strings, graphics, layout files
• Notification Manager
– enables custom alerts to be displayed in status bar
• Activity Manager
– Manages lifecycle of applications and provides
navigation backstack
Application Fundamentals
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Activities
– application presentation layer
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Services
– invisible components, update data sources, visible activities, trigger notifications
– perform regular processing even when app is not active or invisible
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Content Providers
– shareable data store
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Intents
– message passing framework
– broadcase messages system wide, for an action to be performed
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Broadcast receivers
– consume intent broadcasts
– lets app listen for intents matching a specific criteria like location
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Notifications
– Toast notification
– Status Bar Notification
– Dialog notification
Applications
• All apps (native and 3rd party) are written using
the same APIs and run on the same run time
executable
• All apps have APIs for hardware access,
location-based services, support for background
services, map-based activities, 2D and 3D
graphics.
• App Widgets are miniature app views that can
be embedded in other apps like Home Screen
App Priority and Processes
Android apps do not have control over their own
life cycles
Aggressively manages resources to ensure device
responsiveness and kills process/apps when
needed
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Active Process – critical priority
Visible Process – high priority
Started Service Process
Background Process – low priority
Empty process
Client apps
• Developed using the Android SDK and installed
on user devices
• Compiled Java code, with data and resource –
bundled by Android Asset Packaging tool
(AAPT) into Android package or .apk
• All applications have Android Manifest file in its
root directory
– provides essential information about app
• Could be installed directly on phone, but
necessary to be distributed thru Market
Web Apps
• An alternative to standalone apps
• Developed using web standards and
accessed through browser – nothing to
install on devices
• Mixing client and web apps is also
possible – Client apps can embed web
pages using “Webview” in Android app
SDK
• Android APIs, Full Documentation and Sample code
• Development tools
– Dalvik Debug Monitor Service (DDMS)
– Android Debug Bridge (ADB)
– Android Emulator
• Online support and blog
• Native Development Kit also available
– allows developers to implement parts of apps in native-code
languages like C/C++
– Plug in available to use Eclipse integrated development
environment
• Developer forums and developer phones from Google,
MOTO Dev studio from Motorola
Android Market
• Google Market - Part of GMS apps
• 3rd party apps submitted to Google, approved and distributed
through Market
• Both Free and Paid apps
• Apps now limited to 50 MB; updates possible through Market
• Monetization through ads available
• Available in many countries, not all countries have support for paid
apps
• Other Market place applications available – Amazon has announced
its own Android Market place
• App searches filtered based on Manifest file (eg. if a device does not
have trackball, apps using trackball will be filtered out)
• Every app publishes a list of components the app will access and
permissions need to be granted before installation
• Apps installed on device and SD card (SD Card from Froyo)
Search
• Core feature in android
• User should be able to search any data on
device or internet
• Usually one of the android buttons
• Search suggestions based on recent queries
• Provide custom search suggestions that match
actual results in application data
• system side Quick Search Box
• Voice Search available and enhanced in recent
releases
Locations & Maps
• Compelling and most popular apps for
mobile devices
• Google Maps provides free navigation
• applications allowed access to location
services supported by device
• Google provides Maps external library
– allows built-in downloading, rendering and
caching of Maps tiles, and other display
options and controls
Device Administration
• Froyo introduces support for enterprise
applications with Device Administraion API
• allows to create security-aware
applications to control employee devices
• Apps might include
– Email clients
– remote wipe
– device management services and apps
Android Software Updates
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Android 1.0 – G1
1.5 – Cupcake
1.6 – Donuts (CDMA support)
2.0 – Éclair (Droid introduced with Éclair)
2.2 – Froyo
2.3 Gingerbread (SDK released 2 weeks ago and source
will follow soon)
• API Levels used by apps to identify software version on
the device
• Android apps are generally forward compatible with
newer version, but not necessarily backwards
compatible
Compatibility
• Why?
– Allow customizable devices
– Create Common eco system
• Android compatibility is free and easy
– Obtain Android source code
– Comply with Android Compatibility Definition (ACD) doc
• List requirements that need to be met for devices to be compatible
with a particular version on Android
– Pass the Compatibility Test Suite (CTS)
• Automated test harness running on desktop, manages test
exectuion
• Test cases written, packaged as .apk to run on actual device or
emulator
• Porting guide available for bringing up Android on
custom HW
Other possibilities
• Google TV - a new platform based on
Android
• Tablets – Samsung Galaxy tab introduced
in Oct 2010
• eBook reader – Latest Barnes and Noble
Nook is an Android tablet
Resources
• http://www.android.com
• http://http://androiddevelopers.blogspot.com
• http://developer.motorola.com/