1 Android Introduction Based on slides made by Mihail L. Sichitiu and Kesav Kaliyaperumal and also from wikipedia.
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1
Android Introduction
Based on slides made by Mihail L. Sichitiu and Kesav Kaliyaperumal
and also from wikipedia
2
What is Android?
Android is a software stack for mobile devices that includes an operating system, middleware and key applications.
Android OS
an open-source operating system based on the Linux kernel
designed primarily for touchscreen mobile devices such as smartphones and tablet computers
1 billion Android devices have been activated
48 billion apps have been installed
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Phones
HTC G1,Droid,Tattoo
Motorola Droid (X)
Suno S880 Samsung Galaxy Sony Ericsson
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Tablets
Velocity Micro Cruz Gome FlyTouch Acer beTouch
Dawa D7
Toshiba Android SmartBook
Cisco Android Tablet
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MarketShare
Feb’10 May’10 Apr’11
RIM 42.1% 41.7% 29%
Apple 25.4% 24.4% 25%
Google 9% 13% 33%
Microsoft 15.1% 13.2% 7.7%
Palm 5.4% 4.8% 2.9%
Now (November 2013): 80%
Android OS
Interface
Android's user interface is based on direct manipulation: using touch inputs that loosely correspond to real-world actions, like swiping, tapping, pinching and reverse pinching to manipulate on-screen objects.
Android OS
Memory managementAndroid is designed to manage memory (RAM) to keep power consumption at a minimum, in contrast to desktop operating systems which generally assume they are connected to unlimited. When an Android app is no longer in use, the system will automatically suspend it in memory – while the app is still technically "open“.
Android OSMemory managementAndroid manages the apps stored in memory automatically: when memory is low, the system will begin killing apps and processes that have been inactive for a while, in reverse order since they were last used (i.e. oldest first). This process is designed to be invisible to the user, such that users do not need to manage memory or the killing of apps themselves.
Android 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
• Active Process – critical priority• Visible Process – high priority• Started Service Process• Background Process – low priority• Empty process
Linux Kernel and Storage Management
The flash storage on Android devices is split into several partitions, such as /system for the operating system itself, and /data for user data and application installations.
In contrast to desktop Linux, Android device owners are not given root access to the operating system and sensitive partitions such as /system are read-only. However, root access can be obtained by exploiting security flaws in Android.
Software Stack• Linux kernel• Libraries• Android run time
– core libraries– Dalvik virtual machine
• application layer• application protocol
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Android S/W Stack - Application
Android provides a set of core applications: Email Client SMS Program Calendar Maps Browser Contacts Etc
All applications are written using the Java language.
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Android S/W Stack – App Framework
Enabling and simplifying the reuse of components Developers have full access to the same
framework APIs used by the core applications. Users are allowed to replace components.
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Android S/W Stack – App Framework (Cont)Features
Feature Role
View System
Used to build an application, including lists, grids, textboxes, buttons, and embedded web browser
Content Provider
Enabling applications to access data from other applications or to share their own data
Resource Manager
Providing access to non-code resources (localized strings, graphics, and layout files)
Notification Manager
Enabling all applications to display customer alerts in the status bar
Activity Manager
Managing the lifecycle of applications and providing a common navigation backstack
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Android S/W Stack - Libraries
Including a set of C/C++ libraries used by components of the Android system
Exposed to developers through the Android application framework
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Android S/W Stack - Runtime
Core Libraries Providing most of the functionality available in the core
libraries of the Java language APIs
Data Structures Utilities File Access Network Access Graphics Etc
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Android S/W Stack – Runtime (Cont) Dalvik Virtual Machine
Providing environment on which every Android application runs
Each Android application runs in its own process, with its own instance of the Dalvik VM.
Dalvik has been written such that a device can run multiple VMs efficiently.
Register-based virtual machine
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Android S/W Stack – Runtime (Cont) Dalvik Virtual Machine (Cont)
Executing the Dalvik Executable (.dex) format .dex format is optimized for minimal memory
footprint. Compilation
Relying on the Linux Kernel for: Threading Low-level memory management
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