Android Concepts

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What is Android

Android is a software product for mobile devices that has three major parts:

1. operating system
2. middleware
3. applications framework

Android Architecture

Here are the major components based on this [source]

Key principles

1. Linux Kernel - proven driver model, memory and process management, etc. (all the core services of a reliable operating system)

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The second layer has two parts: Libraries and Android runtime.

2.1 Libraries (written in C/C++)

Component	Responsability
Surface Manager	composing drawing surface onto the screen
ES & SGL	core of graphics libraries
Media Framework	core media: mpeg, mp3, all video formats, etc.
FreeType	an engine for rendering fonts
SQLite	core of data storage
WebKit	an open source web browser engine
SSL	security socket layer

2.2 Android Runtime

2.2.1 Core Libraries written in JAVA such as: utils, collection, i/o, etc.

2.2.2 Dalvik Virtual Machine runs dex files (bytecodes efficient for small processors)

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3. Application Framework written completely in Java Programming Language

Application	Functionality
Activity Manager	life cycle of an application - common back stack
Package Manager	keeps track the applications installed of the device
Window Manager	an abstraction layer on top of surface manager
Telephony Manager	Api for telephony applications
Content Providers	application framework that allow applications to share data
Resource Manager	used to store localized layouts, strings, bitmaps, etc.
View System	building blogs of the UI, handles the event dispacher, drawing, etc.
Notification Manager	anables apps to recognize and display common alerts in the status bar