The Design And Implementation Of The Instant Messaging System Based On Android Platform

In recent years, as the rapid development of wireless mobile network and the operating system of the intelligent mobile phone, many kinds of instant messaging software based on wireless Internet also emerge in endlessly. IM, as the means of communication, has been integrated into all aspects of our daily life, and in recent years, with the population of mobile IM applications such as the QQ and Wechat, instant messaging applications have become an important tool for people to communicate.But in the wireless local area network such as campus network, people are not content to just use word and picture for real-time communications. The real-time communication of audio and video is more and more popular in the communications of people. Because in the wireless local area network, the speed of communication is faster and the bandwidth is more big, so we can improve the quality and speed of the file transfer and the communications of audio and video. It can not only satisfy the ordinary demand of communication of people, but also let the file interaction more freely in the phone.Through the analysis of the principle of XMPP protocol and RTP/RTCP protocol, fully considering the characteristics of the wireless local area network, it uses the C/S architecture and peer-to-peer communications architecture, MVC model, and follows the principle of software engineering. The paper makes a whole summary for the design and implementation of instant messaging system based on Android from the requirement analysis of the system, the whole design of the system, the detailed design of the system and the implementation of the system.This system uses the Eclipse as the platform of software development. It uses the open source server named Openfire as the XMPP server. In terms of the data persistence, the database in the server uses MySql database, the database in the client uses the built-in SQLite database in Android. The communication between client and server uses the safe and reliable TCP protocol. The real time communication of audio is based on UDP/RTP protocol of point-to-point communication model, and it uses iLBC to encode the audio signal to ensure the quality of real-time audio call. Due to there is no library of iLBC in the Android platform, so it has to transplant the C library of iLBC to the Android platform. The transplantation need me to study the Android NDK. It can compile and generate the dynamic library through the transplantation of the open source C library of iLBC. And then use the JNI to carry call of the interface.Then introduce the main work of this paper. First of all, it analyze and illustrate the functional requirements and non-functional requirements of the system. Then propose the general design of the system, clear the goals and principles of system design and development, determine the technical architecture of the system, and divide the function modules of the system structure. Then make a detailed analysis and design of each function module, and make the implementation of the system. At the same time, generate the program flow charts, the activity diagram, class diagram, and the core code of the system’s key module. Finally, it points out the deficiency existing in the system and the outlook of the system combined with the fact.Through the above work, finally, the system realize the module of user’s login and registration, friends’management module, buddy chat module, group chat module, personal mood module, voice communication module, file transfer module, voice real-time communication module. And under the environment of Android emulator and the really Android’s phone, the system can run normally and have a good experience.