Sunday, May 02, 2010

Android programming - architecture video

I have been getting interested in Android programming, so I went over to their website and found some introductory videos.

Here's the first one with a little index of what is discussed and my take away from the video.



Video Index:
00:0 Introduction
00:40 Linux Kernel
01:09 Native Libraries
03:09 Android runtime
04:13 Core libraries
04:31 Application framework
07:00 Applications
07:25 Application building blocks
09:37 Example of re-using components in Android
12:18 Conclusion and resources
12:48 End

My Takeaway:

Architecture wise the Android platform has several layers:
  1. Linux Kernel
  2. Native Libraries
  3. Android Runtime
  4. Core Libraries
  5. Application Framework
The applications that we make are build on top of the "application framework" layer.

The Linux Kernel was chosen because of it's stability, services, security, and presence of several device drivers.

Native Libraries consist of various components for rendering graphics and fonts (Surface Manager, OpenGL, SGL, Freetype), a lightweight database engine (SQLLite), a browser engine (WebKit), and others.

The Android Runtime consists of Dalvik the Java Virtual Machine created by Google, which is optimized for running on embedded devices which have low resources. Dalvik runs *.dex files which are created by converting *.jar and *.class files. On top of Dalvik are the core Java libraries consisting of things like the Collections, IO API, etc.

Then the Core libraries layer consists of components such as Activity Manager, Resource Manager, Package Manager, Content Provider, Telephony Manager, XMPP, etc.

Android applications typically have 4 building blocks, which applications mayor may not use. These are:
  1. Activities
  2. Intent Receivers
  3. Services
  4. Content Providers
The video ends with an example of how various applications can re-use a photo picker component. So, we may have multiple applications like email, Blooger, etc which may need to select a photo. These applications do not have to write their own photo picker. They just show an "Intent" to pick a photo, and the component which fulfills that intent will be chosen. This binding is done pretty late, so we can actually change the component that fulfills the intent, and then henceforth that component will be used for that intent.

In the next few blog posts I will be embedding more Android videos along with my learnings.

1 comment:

Loretta Doherty said...

Great, A lovely introduction. Well done!