Android Internals


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Android Internals presentation given to 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  
  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.
  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  
  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  
  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 Licensed under Creative Commons License (cc-by-nc-nd). Please Share!
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