Android Architecture

1. Android Architecture
by Lope Emano

2. The Android Stack

3. Overview
● Linux Kernel Layer
● Native Layer
● Application Framework Layer
● Applications Layer

4. Linux Kernel Layer

5. Linux Kernel Layer Overview
Never really interacts with developers but is the heart of
the whole system.
Android OS is a Linux Fork.
Acts as an interface between device’s hardware and the
upper layers.
Linux is a proven driver model

6. Linux Kernel Layer Overview
Provides following functions to the system:
● Hardware Abstraction
● Memory Management Programs
● Security Settings
● Power Management Software
● Other Hardware Drivers (Drivers are programs that
control hardware devices.)
● Support for Shared Libraries
● Network Stack

7. Android and the Linux Kernel

8. Native Libraries Layer

9. Native Libraries Layer Overview
Libraries carry a set of instructions to guide the device in
handling different types of data.
Libraries handle generating web pages, network security,
decoding music, video files, etc..
Open Source

10. Native Libraries Layer Overview
● Surface Manager: composing windows on the screen
● SGL: 2D Graphics
● Open GL|ES: 3D Graphics Library
● Media Framework: Supports playbacks and recording of
various audio, video and picture formats - codecs
● FreeType: Font Rendering
● WebKit: OpenSource Browser Engine
● libc: System C libraries
● SQLite: Database
● Open SSL: Secured Networking

11. Android Runtime

12. Dalvik Virtual Machine
Open-source software
Written by Dan Bornstein
Named after the fishing village of Dalvík in Eyjafjörður,
Iceland, where some of the author’s ancestors lived
It is the software responsible for running apps on
Android devices
To be replaced by ART which started in Android 4.4
KitKat

13. Dalvik Virtual Machine (more)
● It is a Register based Virtual Machine.
● It is optimized for low memory requirements.
● It has been designed to allow multiple VM instances to
run at once.
● Relies on the underlying OS for process isolation,
memory management and threading support.
● Operates on DEX files.

14. Application Framework Layer

15. Application Framework Layer
Provides many higher-level services to applications in
the form of Java classes.
Application developers are allowed to make use of these
services in their applications.
You will be talking to these guys a lot.

16. Important Blocks
● Activity Manager: Manages the activity life cycle of
applications.
● Content Providers: Manage the data sharing between
applications.
● Telephony Manager: Manages all voice calls. We use
telephony manager if we want to access voice calls in our
application.
● Location Manager: Location management, using GPS or
cell tower
● Resource Manager: Manage the various types of
resources we use in our Application

17. Applications Layer

18. Applications Layer
The applications are at the topmost layer of the Android
stack
An average user of the Android device would mostly
interact with this layer
This is you

19. Applications Layer
Sample applications on this layer:
● SMS client app
● Dialer
● Web browser
● Contact manager

20. What we’ve learned
● Linux serves as the foundation for the Android OS
● There are many layers that help our app run
● These layers abstract themselves as much as
possible s.t. we only need to talk to the Applications
Framework Layer.

21. References:
● http://www.edureka.co/blog/beginners-guide-android-
architecture/
● http://www.tutorialspoint.
com/android/android_architecture.htm
● http://en.wikipedia.org/wiki/Dalvik_%28software%29