introduction - adroid stack

1. Introduction to android platform

2. Agenda
 Android Stack
 Software development

3. Android Software Stack

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

7. Android S/W Stack - Linux Kernel (Cont)
Boot sequence
• Alarm
• Ashmem
• Binder
• Power Management
• Low memory killer
• Kernel debugger
• Logger
Kernel Enhancements

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

13. Android S/W Stack - App Framework (Cont)

14. Android S/W Stack - App Framework (Cont)

15. Android S/W Stack - App Framework (Cont)

16. Android S/W Stack - App Framework (Cont)

17. Android S/W Stack - App Framework (Cont)

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.

19. Android S/W Stack - language

20. Application Architecture

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

25. Questions?