Android Photo frame with source code structure

one. Android Photo Frame

Android Frame level : Android is divided into 4 layers from bottom to top;

-- Linux kernel layer ;

-- various libraries and Android execution Environment layer ;

- application framework layer ;

-- application layer ;

1. Linux kernel layer

the Linux kernel layer of Android : Linux kernel and driver ;

Linux kernel : Android 2.x is based on Linux 2.6 kernel;

Drivers :

-- display Driver ( graphics driver ): Linux frame buffer driver;

-- Flash memory Driver (Flash RAM driver ): MTD-based flash driver;

-- camera Driver : Based on Linux v4l driver;

-- Audio Driver : Based on ALSA driver;

-- WiFi Driver (wifi driver ): Based on the IEEE 801.31 standard driver;

-- KeyBoard Driver ( keyboard driver ): As the input device keyboard driver;

--Bluetooth Driver ( bluetooth® driver ): Wireless transmission technology based on IEEE 801.35.1 standard;

-- Binder IPC Driver : Android-specific driver, with separate device node, providing the function of process communication;

--Power Management : Manage battery power and other information;

Parsing driver :

--  frame buffer (framebuffer) : The video output device contains a video buffer with full frame data, which is used to drive the video display device;

-- v4l (video for Linux) : Camera driver in Linux;

-- ALSA (Advanced Linux sound Architecture) : High-level Linux audio system driver, which provides a sound card driver;

2. Library and Android Execution Environment

This layer is divided into two parts : Android execution Environment and various libraries;

various libraries are introduced : These libraries are provided in the form of system middleware, which is closely related to the application of mobile device platform;

-- C standard library : The bottom of the Android system library, the standard library calls the kernel system calls to implement the required functions;

-- Media Framework ( Multimedia frame ): Android Multimedia Core, is based on the PacketVideo Opencore framework, features an audio video playback, function two audio video recording;

-- SGL : 2D engine;

-- SSL (secure Socket layer): mainly provides security support for the data communication between TCP/IP protocol and Application layer protocol;

-- OpenGL ES : 3D engine;

-- surface Management (Interface management tool): Manage the function of display subsystem;

-- SQLite : Embedded database;

-- WebKit : web browser kernel;

-- FreeType : provides bitmap and vector font functions;

Dalvik virtual machines and JVM differences :

-- Execute file : JVM executes. class standard bytecode file, Dalvik virtual machine executes. dex file;

--The biggest difference : The JVM is a stack-based (stack-based) virtual machine, and the Dalvik virtual machine is a register-based (register-based) virtual machine that can be better optimized based on hardware ;

3. Application Framework Layer

Application Framework Layer : This layer provides the API used by the application, including a variety of UI components and other components, including the following components;

- Activity: the main activities interface;

- broadcastreceiver : Broadcast receivers;

- service: services;

-- ContentProvider : content providers;

4. Application Layer

This layer is the main APK installation program;

two. Android Source code Structure

based on the ANDROID-2.3.4_R1 version number of the source code for analysis ;

Android source code structure Classification :

-- Core part : This part is the foundation of building the Android system, it is saved in the file of the root folder;

-- Extend project: Use parts of other open source projects;

-- Package part : Provides Android application, four components, etc., in the Packages folder;

1. Root folder (/)

Bionic : The source code of the base library, C execution Support library libc, LIBM, LIBDL, dynamic linker;

bootable/bootloader/legacy : Kernel boot loader, the program executed before loading the kernel;

build : The scripts and tools required to compile and configure;

Dalvik : A Java virtual machine in Android that provides the basis for Android application execution;

Development : A high level of templates and tools required for program development;

external : Other open Source extension libraries used;

Frameworks : Application framework layer, four components and so on;

hardware : hardware-related libraries;

kernel : Linux kernel source code;

Packages : Android various applications;

prebuilt : Compiled preset scripts under various platforms;

recovery : Related to Android system recovery function;

system : Android underlying library;

Makefile : The entire Android source code compiled by Makefile;

2. Development folder (/development)

Apps : Android app templates;

build : Compile script template;

host : Some tools of the Windows platform;

Samples : Demo sample program, simple Android program, can be used as a template;

3. External folder (/external)

opencore : Android multimedia frame core;

webkit : Android Web browser core;

sqlite : Android database system core;

OpenSSL : Secure Socket Layer is a network protocol that provides secure support for data communication;

4. Frameworks

base : basic content of Android core Framework library;

opt : Optional part;

Base Folder Contents :

-- Cmds : an important order;

- Core: Kernel library;

- -Data: font sound file;

-- Docs : Documents;

- Graphics: graphic correlation;

- include : header file;

-- KeyStore : Data signing certificate;

-- Libs : library;

- Location: Regional Library;

Media : medium-related library;

-- obex : Bluetooth related library;

-- OpenGL : 3D Graphics library;

-- Packages : Set up a TTS VPN and other libraries;

-- sax : XML parsing;

- Services: various service;

-- Telephony : telephone communication management;

-- Test-runner : Test tool related;

- Test : various tests;

- Tools: a variety of instruments;

-- VPN :

-- WiFi :

5. Packages folder (/packages)

Apps : various apps in Android;

providers : Save content provider information;

inputmethod : Input method;

wallpapers : wallpaper;

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Android Photo frame with source code structure