Abstract: According to the problem of the traditional entity flea market which isn’t real-time and efficient,under the Android platform,campus second-hand transaction application which is also called university online flea market was designed and developed.The reliability of the trading,updating in real time and efficiently searching items were redefined to using college student id register and information classification.Meanwhile,asynchronous loading method was adopted,and interfaces and abstract classes were defined to manage the communication between the server and the client.Compared with the real flea market and online secondary trading platform,the proposed application not only improves the trading efficiency for college students,but also improves the reliability and security.

Key words: Second-hand transactions,Android,Real-name registration,Asynchronous loading,Online flea market