4. Android S/W Stack - Linux Kernel
Android Runs on Linux
•Android is based on the Linux kernel
• Android is not Linux
• No native windowing system
• No glibc
• Does not include full set of standard linux utilities
• Kernel source at http://git.android.com
Providing an abstraction layer between the H/W and the rest of the S/W stack
Relying on Linux Kernel 2.6 for core system services and uses only "Kernel" portion in Linux
Memory and Process Management
Network Stack
Driver Model
Security
• The supplied device drivers include Display, Camera, Keypad, WiFi, Flash Memory, Audio, and IPC
(inter-process communication).
• Adb command opens linux shell
5. Why Linux kernel for Android ?
•Great memory and process management
•Great permissions based security model
• Proven driver model
•Support for shared libraries
• It’s already open source
6. Android S/W Stack - Linux Kernel (Cont)
Typical Directory Tree of Android
8. 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
9. Android S/W Stack - Runtime
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 so that a device can run multiple VMs efficiently.
Register-based virtual machine
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
executes dex code, which is translated
from Java byte code
16bit, register based
cf. Java bytecode is 8bit, stack based
10. 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
Libc: Stucture c standard lib.
SSL: Secure Socket Layer
SGL: Underling 2D grapics engine
OpenGL|ES: 3D image engine
Media Framework: Core part of
Android multi-media –
MPEG4,H.264,MP3,AAC,AMR,JPG,P
NG
SQLite: Light wait relational Embedded
database
WebKit: Kernel of web browser
FreeType: Bitmap and Vector font
renderer
SufraceManager: Manage difference
windows for different applications
11. Android S/W Stack - Libraries
• The media libraries are based on PacketVideo’s
(http://www.packetvideo.com/) OpenCORE. These libraries are
responsible for recording and playback of audio and video
formats.
• A library called Surface Manager controls access to the display
system and supports 2D and 3D.
• The WebKit library is responsible for browser support; it is the
same library that supports Google Chrome and Apple Inc.’s
Safari.
• The FreeType library is responsible for font support.
• SQLite (http://www.sqlite.org/) is a relational database that is
available on the device itself. SQLite is also an independent open
source effort for relational databases and not directly tied to
Android. You can acquire and use tools meant for SQLite for
Android databases as well.
12. Android S/W Stack - App Framework
Most of the application framework accesses these core libraries through the Dalvik VM, the
gateway to the Android Platform
An application can broadcast its capabilities so that other applications can reuse these
functionalities
View System Used to build an application, including lists, grids, text boxes, 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 string, 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
18. Android S/W Stack - Application
Android provides a set of predefined core applications, which handles the phone basic features
These are replaceable applications
Examples :
Email Client
SMS Program
Calendar
Maps
Browser
Contacts
Etc
All applications are written using the Java language.
21. Software development
•Development requirements
• Java
• Android SDK
•IDE and Tools
•Android SDK
Class Library
Developer Tools
Emulator and System Images
Documentation and Sample Code
•Eclipse IDE + ADT (Android Development Tools)
Reduces Development and Testing Time
Makes User Interface-Creation easier
Makes Application Description Easier
22. Android SDK
android.jar Java archive file containing all of the Android SDK classes necessary to build
your application.
documention.html and docs directory The SDK documentation is provided locally and
on the Web. It's largely in the form of JavaDocs, making it easy to navigate the many
packages in the SDK. The documentation also includes a high-level Development Guide and
links to the broader Android community.
Samples directory The samples subdirectory contains full source code for a variety of
applications, including ApiDemo, which exercises many APIs. The sample application is a
great place to explore when starting Android application development.
Tools directory Contains all of the command-line tools to build Android applications. The
most commonly employed and useful tool is the adbutility (Android Debug Bridge).
Usb_driverDirectory containing the necessary drivers to connect the development
environment to an Android-enabled device, such as the G1 or the Android Dev 1 unlocked
development phone. These files are only required for developers using the Windows
platform.
23. Android Tools
Emulator
Android applications may be run
on a real device or on the Android
Emulator, which ships with the
Android SDK.
•ADB (Android Debug Bridge)
The ADB utility lets you connect
to the phone itself and issue
rudimentary shell commands,
such as copying files to and from
the device
24. Advantages
Benefits
Open Platform/License Free
Robust OS Kernel, Innovative Library Packages
Ease App. Development
Rapid Improvement
Challenges
Performance Consideration
Hard to Integrate for Vendors
Too Much Google Dependent
Key Factor: Market Response