1. Bundle savedInstanceState
it is not persist. it does not share between activities, it is nolyfor one activity. it is saved for soft kill like:
1. orientation changes
2. when the process is killed by android due to low memory
hard kill like:
1. finish()
2. back bottom
will destroy it.
原文：http://www.cnblogs.com/phoenix13suns/p/4055684.html