android安卓系统架构

android安卓系统架构android system architecture and their operating systems, using a layered architecture. From the chart to see, android is divided into four layers, from the top to the lower are the application layer, application framework layer, layer and runtime system linux core layer.1. ApplicationAndroid together with a set of core application packages distributed with the application package including email client, SMS Short Message program, calendar, maps, browser, contact management programs. All applications are written using JAVA.2. Application FrameworkDevelopers also have full access to the core application framework API uses. The application architecture simplifies the reuse of components; any application can publish its function blocks and any other application can use it publish function blocks (but must follow security restrictions framework). Similarly, the application reuse mechanism also allows users to easily replace the component.Hidden behind each application is a series of services and systems, including;* Rich and scalable view (Views), it can be used to build applications, which includes a list (lists), grid (grids), a text box (text boxes), buttons (buttons), and even an embeddable web browser device.* Content provider (Content Providers) allows applications to access data from another application (such as a contact database), or share their own data* Resource Manager (Resource Manager) to provide access to non-code resources such as localized strings, graphics, and layout file (layout files).* Notification Manager (Notification Manager) allows applications to display a custom message in the status bar.* Activity Manager (Activity Manager) to manage the application lifecycle and provides common navigation retract function.For more details and how to write an application from scratch, refer to how to write an Android application.3. The system runtime1) LibraryAndroid contains some C / C ++ libraries, which can be different Android system components. They provide services through the Android application framework for developers. The following are some of the core library:* System C library - a BSD to inherit from the standard C system library (libc), which is designed for embedded linux based devices customized.* Media Libraries - based on PacketVideo OpenCORE; The library supports many popular audio and video format playback and recording, support still image files. Encoding formats including MPEG4, H.264, MP3, AAC, AMR, JPG, PNG.* Surface Manager - display management subsystem, and a plurality of applications provides seamless integration of 2D and 3D layers.* LibWebCore - a new web browser engine used to support the Android browser and an embeddable web view.* SGL - the underlying 2D graphics engine* 3D libraries - based on OpenGL ES 1.0 APIs to achieve; the library can use hardware 3D acceleration (if available) or the use of highly optimized 3D software acceleration.* FreeType - bitmap (bitmap) and vector (vector) font.* SQLite - a for all applications available, powerful lightweight relational database engine.2) Android RuntimeAndroid includes a core library, the library provides most of the core functionality JAVA programming language core library.Every Android application runs in its own process to run, have a separate instance of the Dalvik virtual machine. Dalvik is designed as a device can efficiently run multiple virtual systems. Dalvik virtual machine (.dex) of Dalvik executable file, the file format for the small memory usage optimized. While the virtual machine is register, all the classes are compiled via the JAVA-based compiler, and then through the SDK "dx" tool transforming into .dex format executed by the virtual machine.Dalvik VM relies on some of the linux kernel functions, such as thread and mechanisms underlying memory management mechanism.4.Linux kernelAndroid's core system services rely on the Linux 2.6 kernel, such as security, memory management, process management, network stack, and driver model. Linux kernel also as an abstraction layer between the hardware and software stack.android的系统架构和其操作系统一样，采用了分层的架构。

从架构图看，android分为四个层，从高层到低层分别是应用程序层、应用程序框架层、系统运行库层和linux核心层。

1.应用程序Android会同一系列核心应用程序包一起发布，该应用程序包包括email客户端，SMS短消息程序，日历，地图，浏览器，联系人管理程序等。

所有的应用程序都是使用JAVA语言编写的。

2.应用程序框架开发人员也可以完全访问核心应用程序所使用的API框架。

该应用程序的架构设计简化了组件的重用；任何一个应用程序都可以发布它的功能块并且任何其它的应用程序都可以使用其所发布的功能块（不过得遵循框架的安全性限制）。