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How to analyze the basic mode of Android system architecture, many novices are not very clear about this. In order to help you solve this problem, the following editor will explain it in detail. People with this need can come and learn. I hope you can get something.

Nowadays, people are bound to be dazzled by the wide variety of mobile phones in the market. However, in today's smartphone-dominated era, the main factor in choosing a mobile phone is to choose a high-performance mobile operating system, and Android is one of the inevitable choices. Android system architecture, like its operating system, adopts a hierarchical architecture. Android is divided into four layers. From high level to low level, they are application layer, application framework layer, system runtime layer and linux core layer.

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Application of Android system Architecture

Android is released with a series of core application packages, including email client, SMS short message program, calendar, map, browser, contact manager, etc. All applications are written in Java.

Application Framework of Android system Architecture

Developers also have full access to the API framework used by core applications. The architectural design of the application simplifies the reuse of components; any application can publish its functional blocks and any other application can use its published functional blocks (subject to the security limitations of the framework). Similarly, the application reuse mechanism also enables users to easily replace program components.

Hidden behind each application is a range of services and systems, including

* Rich and extensible views (Views) can be used to build applications, including lists, grids, text boxes, buttons, and even embedded web browsers.

* content providers (Content Providers) enable applications to access data from another application (such as a contact database) or share their own data

* Resource Manager (Resource Manager) provides access to non-code resources such as local strings, graphics, and layout files (layout files).

* Notification Manager (Notification Manager) enables applications to display custom prompts in the status bar.

* the activity Manager (Activity Manager) is used to manage the application lifecycle and provide common navigation fallback functions.

For more details and how to write an application from scratch, please refer to how to write an Android application.

System Runtime Library of Android system Architecture

1) Program library

Android contains a number of Candlestick + libraries that can be used by different components in the Android system. They provide services to developers through the Android application framework. Here are some core libraries:

* system C Library-A standard C system function library (libc) inherited from BSD, which is customized for embedded linux-based devices.

* Media Library-based on PacketVideo OpenCORE;, this library supports playback and recording of a variety of commonly used audio and video formats, as well as still image files. Encoding formats include MPEG4, H.264, MP3, AAC, AMR, JPG, PNG.

* Surface Manager-management of the display subsystem and seamless fusion of 2D and 3D layers for multiple applications.

* LibWebCore-A * * web browser engine that supports Android browsers and an embeddable web view.

* SGL-the underlying 2D graphics engine

* 3D libraries-based on OpenGL ES 1.0 APIs; the library can use hardware 3D acceleration (if available) or highly optimized 3D soft acceleration.

* FreeType-bitmap (bitmap) and vector (vector) fonts are displayed.

* SQLite-A powerful lightweight relational database engine available for all applications.

2) Android Runtime

Android includes a core library that provides most of the functionality of the JAVA programming language core library.

Each Android application runs in its own process and has a separate Dalvik virtual machine instance. Dalvik is designed to run multiple virtual systems efficiently on one device at the same time. The Dalvik virtual machine executes (.dex) Dalvik executable files, which are optimized for small memory usage. At the same time, the virtual machine is register-based, and all classes are compiled by the JAVA compiler and then converted to .dex format by the "dx" tool in SDK.

The Dalvik virtual machine relies on some functions of the linux kernel, such as the threading mechanism and the underlying memory management mechanism.

Linux Kernel of Android system Architecture

Android's core system services rely on the Linux 2.6 kernel, such as security, memory management, process management, network protocol stack and driver model. The Linux kernel also acts as an abstraction layer between the hardware and software stacks.

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