1. Introduction to Android
Christophe Beyls
Jeudis du Libre - April 2012

2. About the speaker
● Developer living in Brussels.
● Uses various programming languages,
mostly Java and C#.
● Likes coding, hacking devices, travelling,
movies, music, (LOL)cats.
● Worked for:

3. Agenda
1. Introduction - Why Android?
2. History
3. System architecture and its free parts
4. The SDK
5. The building blocks of an Android
app
6. Devices hacking and custom ROMs
7. Questions & Answers.

4. Why Android?

5. Why Android?

6. Why Android?
■ Open architecture.
■ Apps may be distributed outside the Google
Play Store (Android Market) and installed on
any device.

7. History
■ 2003: Android Inc.
founded by Andy Rubin.
■ 2005: Purchase by Google.
■ January 2007: Apple announces
the iPhone.
■ June 2007: iPhone released.

8. History
November 2007
Google creates the Open Handset Alliance
consortium with 34 founding members.
Manufacturers: HTC, LG, Sony, Motorola,
Samsung.
Semiconductors: Qualcomm, Intel, nVidia, ...
Operators: T-Mobile, Sprint, Telefónica...
Software: eBay, Google, Nuance, ...

9. History
November 2007: First beta SDK released.

10. History
December 2007: Early prototype unveiled.

11. History
February 2008: Apple releases the iPhone
SDK.
June 2008: Apple opens the App Store and
releases the iPhone 3G.

12. History
September 2008
Android 1.0 on HTC Dream (T-Mobile G1).

13. History
February 2009: Android 1.1 (bugfixes).
April 2009: Android 1.5 Cupcake
(Widgets, virtual keyboard).
June 2009: 2 more Android phones released.
HTC Magic HTC Hero
September 2009: Android 1.6 Donut
(Text-to-speech, multiple screen resolutions).

14. History
November 2009: Android 2.0 Eclair
(HTML5, Contacts + Bluetooth APIs).
January 2010: Nexus One released
(first Google-branded phone).
Android 2.1 (bugfixes, live wallpapers).
April 2010: Apple iPad released.
May 2010: Android 2.2 FroYo
(speed, JIT compiler, push notifications, Adobe
Flash support, WiFi hotspot).

15. History
2Q10: Android outsells iOS devices worldwide.

16. History
December 2010: Android 2.3 Gingerbread
on Google Nexus S.
(Black interface, NFC, native SIP,
WebM support)

17. History
February 2011: Android 3.0 Honeycomb
on the first Android tablet: the Motorola Xoom.
■ New UI: Holo theme, Fragments, Action Bar
■ Full 2D hardware acceleration.

18. History
3Q11: Android market share doubles compared
to 3Q10 and becomes to most used mobile OS.

19. History
November 2011:
Android 4.0 Ice Cream Sandwich
on Google/Samsung Galaxy Nexus.
■ Unified OS for Smartphones
and Tablets.
■ Faster, smoother
■ Improved browser
■ Roboto font
■ Face unlock.

20. System Architecture

21. System architecture - Bionic libc
■ Fast, optimized for ARM
■ Lightweight (200 ko), half the size of glibc
■ No C++ Exceptions
■ No Standard Template Library
■ New pthreads implementation
[does not support pthread_cancel()]
■ Can be exploited directly through NDK
(native development kit)
BSD licence
https://github.com/android/platform_bionic

22. System architecture - WebKit
■ Developed by KDE, Apple, Nokia, Google
and others.
■ Android 2.2+ uses faster V8 javascript
engine instead of JavascriptCore.
■ No differences between Android browser
and webviews embedded in apps.

23. System architecture -
Media Framework
Based on OpenCORE and Stagefright (2.2+).

24. System architecture -
Media Framework - Base support
■ Audio codecs: AAC, MP3, AMR, PCM,
MIDI, Ogg Vorbis, FLAC (3.1+)
■ Image codecs: JPEG, GIF, BMP, PNG,
WebP (4.0+)
■ Video codecs: H.263, H.264, MPEG-4 SP,
VP8 (2.3.3+)
■ Containers: 3GPP, MPEG-4,
Matroska (.mkv) (4.0+)
■ Manufacturers may add more codecs.
Italic = patent-free

25. System architecture - Runtime
■ Android uses only the Java language,
not the Java platform.
■ Dalvik Virtual Machine developed by
Google.
■ Uses minimal memory.
■ Java bytecode is converted to smaller
Dalvik bytecode at build time (.dex files).
■ Uses Just-In-Time compilation since
Android 2.2 for better performance.
■ Standard library is based on Apache
Harmony open source implementation.

26. Android Open Source Project
(AOSP)
source.android.com

27. Android Open Source Project
(AOSP)
Almost... fully open:
■ Google publishes source code when they
decide it.
■ No real interaction with Google teams.
■ Not everything is open source:
○ Proprietary binary drivers
○ Google Apps: Google Maps, Gmail, Google
Contacts/Calendar/Bookmarks Sync, Google Talk,
Play Store (Android Market), Youtube, Weather
widget, Text-To-Speech, Voice Search.

28. The SDK
iPhone / iPad
■ Hardware: Mac (with latest Mac OS X)
■ IDE: XCode (free)
■ Language: Objective-C.
Windows Phone 7 / Windows 8
■ Hardware: PC with Microsoft Windows
■ IDE: Microsoft Visual Studio (free)
■ Language: C#, Visual Basic.

29. The SDK
Android
■ Hardware: Any x86
■ IDE: Eclipse, Netbeans, IntelliJ IDEA
■ Language: Java.

30. Installing the SDK
developer.android.com/sdk

31. Official SDK Tools
■ ADB (Android Debug Bridge)
■ ARM Emulator (based on QEMU)
■ DDMS (Dalvik Debug Monitor Server)
■ Proguard (Java optimizer & obfuscator)
■ ADT Plugin for Eclipse:
○ Project wizards
○ Java editor with code completion, refactoring, ...
○ Lint integration
○ Visual layout editor
+ NDK (Native Development Kit)

32. Official SDK Tools - ADT Plugin

33. Official SDK Tools - ADT Plugin

34. Official SDK Tools - ADT Plugin

35. Official SDK Tools - ADT Plugin
Resources
■ By language
■ By screen density
■ By screen orientation
■ By Android version

36. Official SDK Tools - ADT Plugin

37. User Interface
developer.android.com/design

38. Android apps: the building blocks
Activities: screens with a life cycle.

39. Android apps: the building blocks
Fragments: portions of screens with a life
cycle.

40. Android apps: the building blocks
■ Background services.
■ Intents: IPC mechanism between
Activities and/or Services.
Action + Data
○ Action: View, Edit, Dial, ..., custom actions
○ Data: URL scheme or any MIME type.
■ Everything in the system use intents
and is interchangeable.

41. Android apps: the building blocks
Special apps:
■ Live wallpapers
■ Widgets

42. Diversity
Development challenges:
■ Write fast high-level code or use NDK
■ Support multiple devices types
○ Phones
○ Tablets
○ Google TVs
■ Support multiple Android versions.

43. Diversity - Android versions

44. Diversity - Android versions
99%

45. Diversity - Android versions
Use features of newer Android versions
while staying compatible with older runtimes:
Isolate special functionality in separate classes.
MyInterface implementation;
if (Build.VERSION.SDK_INT >=
Build.VERSION_CODES.FROYO)
implementation = new FroYoImplementation();
else
implementation = new CompatibleImplementation();

46. The upgrade problem
Manufacturers provide custom user interfaces.
Sony Ericsson
HTC Sense Timescape Samsung TouchWiz

47. The upgrade problem
■ Updating the custom user interface to a new
Android version requires a lot of work.
■ Manufacturers focus on selling you their
latest hardware, not providing support for
older hardware.
■ On Android, upgrades usually depend on
carriers. (The Proximus case)
■ Many manufacturers don't do OTA updates.
■ Average official support time:
○ 3 years for Apple
○ <= 2 years for most Android phones.

48. The upgrade solution:
Installing community ROMs
Why hack ?
■ Give choice to the user.
■ Remove bloatware.
■ Provide longer term support and upgrades.
Custom ROMs:
Complete firmware (OS, UI, base applications)
created by the community.

49. Hacking - Custom ROMs
Different kinds of custom ROMs:
■ Modified original vendor versions
■ Ported from another device (experimental)
■ Build from source (AOSP)
Hack challenges
■ Locked hardware (HTC S-ON).
■ Binary drivers:
Radio (Wifi - Bluetooth - GPS), Graphics,
NFC, sometimes accelerometers.

50. Hacking
Warning: voids warranty.
Successfully hacked:
HTC G1, HTC Magic, HTC Hero, HTC Desire,
HTC Legend, Dell Streak, Samsung Galaxy S,
Samsung Galaxy Gio, Samsung Galaxy Tab,
Acer Liquid, ZTE Blade, Motorola Xoom,
Sony Ericsson Xperia X10.

51. Hacking - The Bible
forum.xda-developers.com

52. Hacking - Custom ROMs
Cyanogenmod - www.cyanogenmod.com

53. Hacking - Custom ROMs
MIUI - miuiandroid.com

54. Hacking basics
■ ROM Bootloader
IPL SPL Kernel
■ Recovery Recovery
Radio
Boot modes: System
■ Normal OS
■ Recovery
■ SPL (Flash mode) Data

55. Hacking basics
Custom ROM:
Zip file containing
■ system files
■ kernel
■ optionnally radio.
Can be installed easily
using a custom recovery.

56. Hacking basics - 1. Flash tools
FastBoot (Google, HTC, Sony Ericsson)
■ Android standard command line Flash Tool
■ Available in the SDK (Win, Mac, Linux)
■ Useful commands:
fastboot oem unlock
fastboot flash recovery recovery.img
fastboot boot recovery.img
fastboot erase data -w

57. Hacking basics - 1. Flash tools
Samsung ODIN (Windows)

58. Hacking basics - 2. Root access
■ Root access allows to perform restricted
operations like:
○ writing files on system partition
○ flashing a custom recovery directly from Android
OS.
■ It requires:
○ Patching or replacing the kernel
○ - or -
○ Use phone-specific kernel exploits
(mainly through ADB).

59. Hacking basics - 2. Root access

60. Recap: How to change your ROM
1. Go to a forum / wiki and learn the procedure
2. Use:
a. fastboot
b. the vendor flash tool
c. a root hack
to install a custom recovery on your phone.
3. Download a custom ROM as zip file and
place it to your SD card/internal storage.
4. Reboot your phone in custom recovery and
install the ROM. Reboot. Done.

61. Hacking basics - Custom recovery
ClockworkMod
recovery

62. Hacking basics - Custom recovery

63. Thank you for watching.
Questions?
Twitter: @BladeCoder
Web: digitalia.be