Marakana Android Internals
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This document discusses Android internals and provides an overview of the Android stack. It describes the Linux kernel, Dalvik VM, application framework, and native development kit. It explains how applications interact with the runtime and native libraries using Binder IPC and the Java native interface. The document also covers operating system features like security, file systems, and the startup process.
Marakana Android Internals
- 1. Android Internals Marko Gargenta Marakana
- 2. Agenda • Android Stack • Opera6ng System Features • Android Startup & Run6me • Layer Interac6on • Na6ve Development Kit • Summary
- 4. The Stack
- 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. Na6ve Libraries Bionic, a super fast and small Applications license-friendly libc library Home Contacts Phone Browser Other optimized 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. 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. Android and Java Android Java = Java SE – AWT/Swing + Android API
- 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. Applica6ons
- 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. 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. ANDROID STARTUP & RUNTIME
- 16. Run6me Overview
- 17. 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.
- 18. App – Run6me Service -‐ Lib
- 19. App – Run6me-‐Na6ve Service-‐Lib
- 21. Binder IPC High-performance IPC: shared memory, per-process thread pool, synchronous
- 22. 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.
- 23. Building and Running JNI Code
- 25. 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
- 26. 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.
- 27. Using NDK
- 28. 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 build your own Android platform from source. Marko Gargenta, Marakana.com marko@marakana.com +1-415-647-7000 Licensed under Creative Commons License (cc-by-nc-nd). Please Share!