参考：

Android_onRetainNonConfigurationInstance和getLastNonConfigurationInstance

http://www.cnblogs.com/dengxianzhi/articles/2248655.html

onSaveInstanceState() 和 onRestoreInstanceState()

http://www.cnblogs.com/hanyonglu/archive/2012/03/28/2420515.html

Android中activity保存状态的几个放大的使用