http://blog.csdn.net/visualeleven/article/details/6041893
http://blog.csdn.net/visualeleven/article/details/6088590
http://blog.csdn.net/visualeleven/article/details/5991743
http://blog.csdn.net/visualeleven/article/details/6011417
原文：http://www.cnblogs.com/findumars/p/6006041.html