原理介绍:
http://blog.csdn.net/huahuagongzi9999/article/details/8886437
Demo下载:
http://download.csdn.net/download/jasonzhou613/5313265
http://download.csdn.net/download/kedongjun/5339120
http://download.csdn.net/detail/bowang3/5002057
http://download.csdn.net/detail/huanghr_1/4463942