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This article introduces the relevant knowledge of "what are the characteristics of Android". In the actual case operation process, many people will encounter such difficulties. Next, let Xiaobian lead you to learn how to deal with these situations! I hope you can read carefully and learn something!

What is Android?

Android is a software set specifically for mobile devices, which includes an operating system, middleware and some important applications. The Android SDK provides the tools and APIs necessary for Android app development using JaVa on the Android platform.

Android Features

Application frameworks support reuse and replacement of components

· Dalvik VMs optimized for mobile devices

Integrated browser based on open source WebKit engine

Optimized graphics library includes custom 2D graphics library, 3D graphics library based on OpenGL ES 1.0 (hardware acceleration optional)

SQLite is used as a structured data store

Multimedia support includes common audio, video and still image formats (e.g. MPEG4, H.264, MP3, AAC, AMR, JPG, PNG,GIF)

GSM telephone technology (hardware dependent)

Bluetooth, EDGE, 3G, and WiFi (hardware dependent)

Camera, GPS, compass, and accelerometer (hardware dependent)

Rich development environment including device simulators, debugging tools, memory and performance analysis charts, and Eclipse IDE plug-ins.

application framework

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

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

Rich and extensible Views that can be used to build applications, including lists, grids, text boxes, buttons, and even embeddable web browsers.

Content Providers enable applications to access another application's data (such as a contacts database) or share their own data

Resource Manager provides access to non-code resources such as native strings, graphics, and layout files.

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

Activity Manager is used to manage the application lifecycle and provide common navigation fallback features.

library

Android includes a number of C/C++ libraries that can be used by different components of the Android system. They're delivered through the Android app framework

Services for developers. Here are some core libraries:

System C Library-A standard C system library (libc) inherited from BSD, tailored specifically for embedded linux based devices.

·Media library-based on PacketVideo OpenCORE; the library supports playback and recording of multiple popular audio and video formats, as well as still image files. Coding formats include MPEG4, H.264, MP3, AAC, AMR, JPG, PNG.

SurfaceManager-manages the display subsystem and provides seamless blending 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 and vector font display.

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

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 VM instance. Dalvik was designed

A single device can efficiently run multiple virtual systems simultaneously. Dalvik virtual machine execution (.dex) Dalvik executable file, this format text

It is optimized for small memory usage. The virtual machine is register-based, and all classes are compiled via the JAVA compiler and then passed through the SDK.

The "dx" tool in is converted to.dex format for execution by the virtual machine.

The Dalvik VM relies on features of the Linux kernel, such as threading and underlying memory management.

Linux kernel

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 hardware and software stacks.

Android apps and frameworks

The figure below shows the main components of the Android system.

Core applications such as Contacts, Email, Phone, Browser, Calendar, Maps,…

Full access to all core application framework APIs

C/C++ libraries: used by various Android components through the application framework developers can use its features include:

Media Library: MPEG4 H.264 MP3 PNG...

WebKit/LibWebCore: Web browsing engine

SQLite Relational Database Engine

2D, 3D graphics libraries, engines

Android uses Java as its development language, and a large portion of its libraries are shared with Java SE, but unlike Java ME, the Dalvik VM is not a Java VM either. Eclipse is Android recommended development IDE, Android platform comes with a variety of applications such as contacts, e-mail, phone, browser, calendar, maps can be rewritten.

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