来源：http://www.cnblogs.com/lyp3314/archive/2011/11/10/2244971.html
http://www.ibm.com/developerworks/cn/opensource/os-cn-android-actvt/
http://xifangyuhui.iteye.com/blog/810911
andriod activity
原文：http://www.cnblogs.com/sonice-cinsy/p/4359947.html
