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Android	
  
 Internals	
  


Marko	
  Gargenta	
  
  Marakana	
  
Agenda	
  
•    Android	
  Stack	
  
•    Opera6ng	
  System	
  Features	
  
•    Working	
  with	
  Hardware	
  
•    And...
ANDROID	
  STACK	
  
The	
  Stack	
  
Linux	
  Kernel	
  
Android runs on Linux.                                        Applications


                         ...
Na6ve	
  Libraries	
  
Bionic, a super fast and small                                Applications


GPL-based libc library...
Dalvik	
  
Dalvik VM is Google’s implementation of Java

Optimized for mobile devices




Key Dalvik differences:

    Reg...
Android	
  and	
  Java	
  
Applica6on	
  Framework	
  
Activation manager controls the life                              Applications


cycle of the ...
Applica6ons	
  
OPERATING	
  SYSTEM	
  FEATURES	
  	
  
File	
  System	
  
The file system has three main mount points. One
for system, one for the apps, and one for whatever.

E...
Security	
  
Each Android application            Android Application
runs inside its own Linux
process.                   ...
WORKING	
  WITH	
  HARDWARE	
  
Camera	
  
Android SDK supports access to
built-in Camera and its preview.

You can access real-time frames,
or get a call...
WiFi
                                      	
  
WiFi API allows for managing your
connection, scanning for active WiFi
poi...
Telephony
                                     	
  
With Telephony API, you can:

Make phone calls
Monitor phone state and...
ANDROID	
  	
  
STARTUP	
  &	
  	
  
RUNTIME	
  
Startup	
  Walkthrough	
  
Run6me	
  Overview	
  
Layer	
  Interac6ons
                                     	
  
There are three main
scenarios for your app to talk
to nati...
App	
  –	
  Run6me	
  Service	
  -­‐	
  Lib	
  
App	
  –	
  Run6me-­‐Na6ve	
  Service-­‐Lib	
  
App–Run6me–Na6ve	
  Daemon-­‐Lib	
  
Binder	
  IPC	
  




High-performance IPC: shared memory, per-process thread pool, synchronous
Java	
  Na6ve	
  Interface	
  

JNI defines naming and coding
convention so that Java VM can find
and call native code.

J...
Building	
  and	
  Running	
  JNI	
  Code	
  
NATIVE	
  
DEVELOPMENT	
  
KIT	
  
What’s	
  in	
  NDK?	
  
Tools to build and compile your native code for the device
architecture (such as ARM)


A way to ...
Why	
  NDK?	
  

NDK allows you to develop parts of your Android
application in C/C++.

You cannot develop native-only app...
Using	
  NDK	
  
DEBUGGING	
  	
  
ANDROID	
  APPS	
  
LogCat
                              	
  
The universal, most
versatile way to track
what is going on in
your app.

Can be...
Debugger
                                    	
  




Your standard debugger is included in SDK, with all the usual bells ...
TraceView	
  




TraceView helps you profile you application and find bottlenecks. It shows
execution of various calls th...
Hierarchy	
  Viewer
                                          	
  
Hierarchy Viewer helps
you analyze your User
Interface....
Summary	
  
     For most applications, you will just
     need Android SDK to develop apps.

     Sometimes you may need ...
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Android Internals

Android Internals presentation given to SFAndroid.org on Feb 23, 2010.

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Android Internals

  1. 1. Android   Internals   Marko  Gargenta   Marakana  
  2. 2. Agenda   •  Android  Stack   •  Opera6ng  System  Features   •  Working  with  Hardware   •  Android  Startup  &  Run6me   •  Na6ve  Development  Kit   •  Debugging   •  Summary  
  3. 3. ANDROID  STACK  
  4. 4. The  Stack  
  5. 5. Linux  Kernel   Android runs on Linux. Applications Home Contacts Phone Browser Other Linux provides as well as: Hardware abstraction layer Application Framework Memory management Activity Window Content View Process management Manager Manager Providers System Package Telephony Resource Location Notiication Networking Manager Manager Manager Manager Manager Libraries Users never see Linux sub system Surface Media SQLite Android Runtime Manager Framework Core Libs The adb shell command opens OpenGL FreeType WebKit Delvik Linux shell SGL SSL libc VM Display Camera Linux Kernel Flash Binder Driver Driver Driver Driver Keypad WiFi Audio Power Driver Driver Driver Mgmt
  6. 6. Na6ve  Libraries   Bionic, a super fast and small Applications GPL-based libc library optimized Home Contacts Phone Browser Other for embedded use Application Framework Surface Manager for composing Activity Window Content View window manager with off-screen Manager Manager Providers System buffering Package Telephony Resource Location Notiication Manager Manager Manager Manager Manager Libraries 2D and 3D graphics hardware Surface Media SQLite Android Runtime support or software simulation Manager Framework Core Libs OpenGL FreeType WebKit Delvik Media codecs offer support for SGL SSL libc VM major audio/video codecs Display Camera Linux Kernel Flash Binder Driver Driver SQLite database Driver Driver Keypad WiFi Audio Power Driver Driver Driver Mgmt WebKit library for fast HTML rendering
  7. 7. Dalvik   Dalvik VM is Google’s implementation of Java Optimized for mobile devices Key Dalvik differences: Register-based versus stack-based VM Dalvik runs .dex files More efficient and compact implementation Different set of Java libraries than SDK
  8. 8. Android  and  Java  
  9. 9. Applica6on  Framework   Activation manager controls the life Applications cycle of the app Home Contacts Phone Browser Other Content providers encapsulate data Application Framework that is shared (e.g. contacts) Activity Window Content View Manager Manager Providers System Package Telephony Resource Location Notiication Resource manager manages Manager Manager Manager Manager Manager everything that is not the code Libraries Surface Media SQLite Android Runtime Manager Framework Location manager figures out the Core Libs location of the phone (GPS, GSM, OpenGL FreeType WebKit Delvik WiFi) SGL SSL libc VM Notification manager for events Display Driver Camera Driver Linux Kernel Flash Driver Binder Driver such as arriving messages, Keypad WiFi Audio Driver Power Mgmt Driver Driver appointments, etc
  10. 10. Applica6ons  
  11. 11. OPERATING  SYSTEM  FEATURES    
  12. 12. File  System   The file system has three main mount points. One for system, one for the apps, and one for whatever. Each app has its own sandbox easily accessible to it. No one else can access its data. The sandbox is in /data/data/com.marakana/ SDCard is expected to always be there. It’s a good place for large files, such as movies and music. Everyone can access it.
  13. 13. Security   Each Android application Android Application runs inside its own Linux process. Linux Process Additionally, each application has its own sandbox file File system with its own set of Prefs DB System preferences and its own database. Other applications cannot access any of its data, unless it is explicitly shared.
  14. 14. WORKING  WITH  HARDWARE  
  15. 15. Camera   Android SDK supports access to built-in Camera and its preview. You can access real-time frames, or get a callback when shutter is open. The photo data is passed back in either raw or jpeg format.
  16. 16. WiFi   WiFi API allows for managing your connection, scanning for active WiFi points and find out details about each.
  17. 17. Telephony   With Telephony API, you can: Make phone calls Monitor phone state and activity Access phone properties and status Monitor data connectivity Control the phone It is a simple yet powerful API
  18. 18. ANDROID     STARTUP  &     RUNTIME  
  19. 19. Startup  Walkthrough  
  20. 20. Run6me  Overview  
  21. 21. Layer  Interac6ons   There are three main scenarios for your app to talk to native library: -  Directly -  Via native service -  Via native daemon It will depend on the type of app and type of native library which method works best.
  22. 22. App  –  Run6me  Service  -­‐  Lib  
  23. 23. App  –  Run6me-­‐Na6ve  Service-­‐Lib  
  24. 24. App–Run6me–Na6ve  Daemon-­‐Lib  
  25. 25. Binder  IPC   High-performance IPC: shared memory, per-process thread pool, synchronous
  26. 26. Java  Na6ve  Interface   JNI defines naming and coding convention so that Java VM can find and call native code. JNI is built into JVM to provide access to OS I/O and others.
  27. 27. Building  and  Running  JNI  Code  
  28. 28. NATIVE   DEVELOPMENT   KIT  
  29. 29. What’s  in  NDK?   Tools to build and compile your native code for the device architecture (such as ARM) A way to package your library into the APK file so you can distribute your application easily A set of native system headers that will be supported for the future releases of Android platform (libc, libm, libz, liblog, JNI headers, some C++ headers, and OpenGL) (some) documentation, sample code and examples
  30. 30. Why  NDK?   NDK allows you to develop parts of your Android application in C/C++. You cannot develop native-only apps in NDK – your app is still subject to security sandboxing. Main motivation for native code is performance.
  31. 31. Using  NDK  
  32. 32. DEBUGGING     ANDROID  APPS  
  33. 33. LogCat   The universal, most versatile way to track what is going on in your app. Can be viewed via command line or Eclipse. Logs can be generated both from SDK Java code, or low-level C code via Bionic libc extension.
  34. 34. Debugger   Your standard debugger is included in SDK, with all the usual bells & whistles.
  35. 35. TraceView   TraceView helps you profile you application and find bottlenecks. It shows execution of various calls through the entire stack. You can zoom into specific calls.
  36. 36. Hierarchy  Viewer   Hierarchy Viewer helps you analyze your User Interface. Base UI tends to be the most “expensive” part of your application, this tool is very useful.
  37. 37. Summary   For most applications, you will just need Android SDK to develop apps. Sometimes you may need NDK to make parts of your app run faster. Ultimately, you can do whatever you want by compiling Android platform from source. Marko Gargenta Marakana.com Licensed under Creative Commons License (cc-by-nc-nd). Please Share!

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