Future-Proofing Your Apps http://developer.android.com/resources/articles/future-proofing.html
xxx
IPC
Winthin the same Application
Activities
startActivityForResult, and then get result in onActivityResult (Refer to http://blog.chinaunix.net/link.php?url=http://www.android1.net%2FTopic.aspx%3FBoardID%3D11%26amp%3BTopicID%3D399)
Use static filed, such as use to register a listener (Please refer to http://blog.chinaunix.net/link.php?url=http://www.android1.net%2FTopic.aspx%3FBoardID%3D11%26amp%3BTopicID%3D415)