Android Architecture Introduction

Source: Internet
Author: User
Tags home screen

Transferred from: http://blog.sina.com.cn/s/blog_4bc996c40100fawo.html

First, operating system layer (OS)
Second, various libraries (Libraries) and Android Runtime Environment (runtime)
Third, application framework (application framework)
Iv. Applications (application)
The following are the key points and related technologies of the software at each level of andoid, respectively:

operating system layer (OS)
Android uses Linux2.6 as the operating system, Linux2.6 is a standard technology, and Linux is also an open operating system. Android's use of the operating system includes both core and driver parts, and Android's Linux core is the standard Linux2.6Kernel, Android is more of a need for some mobile device-related drivers. The main drivers are as follows:
Display Driver: A common Linux-based frame buffer drive.
Flash memory driver (Flash Driver)
Camera driver (camera Driver): Commonly used Linux-based V4L (Video for) drivers.
Audio Driver: Commonly based on ALSA (Advanced Linux sound Architecture, Premium Linux voice system) drivers.
WiFi driver (Camera Driver): IEEE 802.11 standard-based driver
Keyboard driver (KeyBoard Driver)
Bluetooth driver (bluetooth® Driver)
Binder IPC Driver: andoid A special driver with a separate device node that provides the ability to communicate between processes.
Power Management (Energy management)

various libraries (Libraries) and Android Runtime Environment (runtime)
This level corresponds to the general embedded system, equivalent to the middleware level. This level of Android is divided into two parts, one is a variety of libraries, the other is the Android runtime environment. The content of this layer
Most are usedC + +Implemented.
Among them, the various libraries include:
▅C Library: The standard library of C language, which is also the most basic library in the system, and C library is implemented by the system call of Linux.
▅ Multimedia Framework (Mediaframeword): This part is the core part of Android Multimedia, based on PacketVideo (ie, PV) Opencore, from the function of the library altogether
is divided into two parts, one part is audio, video playback (PlayBack), the other part is the audio and video recording (Recorder).
▅sgl:2d image engine.
▅ssl: The secure Socket layer is located between the TCP/IP protocol and various application layer protocols, providing data communicationSafetySupport.
▅opengl ES 1.0: This section provides support for 3D.
▅ Interface management tool (Surface Management): This section provides features such as the management display subsystem.
▅sqlite: A general-purpose embeddedDatabase
▅webkit:NetworkThe core of the browser
▅freetype: Features of bitmap and vector fonts.
Android's various libraries are generally provided in the form of system middleware, all of which have a notable feature is closely related to the application of mobile device platform.

The Android operating environment mainly refers to the virtual machine technology--dalvik. Unlike a generic Java virtual machine (Java VM), a Dalvik virtual machine executes a file that is not a Java standard bytecode (bytecode) but executes in Dalvik executable format (. dex).    In the process of execution, each application is a process (Linux). The biggest difference is that the Java VM is a stack-based virtual machine (stack-based), and Dalvik is a register-based virtual machine (register-based). Obviously, the latter's greatest benefit is that it can be optimized for hardware, which is better suited to the characteristics of mobile devices.

Application Framework (application framework)
Android's application framework for the application layerDevelopmentProvides APIs, which is actually a framework for an application. Because the upper-level applications are built in Java, this
The hierarchy provides first contains the various controls that are required in the UI program:
For example: Views (view components) include lists (list), grids (grid), text boxes (text box), buttons (button), etc. Even an embedded web browser.
An andoid application can take advantage of the following parts of the application framework:
Activity (Activities)
Broadcast Intent receiver (broadcast intent receiver)
Service (services)
Content Provider (contents provider)

Applications (application)
Android applications are primarily user-Interface, usually written in Java programs, which can also contain various resource files (placed in the RES directory) Java programs and related resources are compiled to generate an APK package. Android itself offers many core applications such as Home screen (home), Contacts (contact), telephone (phone), and browser (browers). At the same time the applicationDevelopmentUsers can also implement their own programs using the API of the application framework layer. This is also the embodiment of the huge potential of Android open source.

Android Architecture Introduction

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