This document is primarily about Android local data storage; the ability to store data locally on a mobile device is a critical feature for applications that need to maintain important information across the execution or lifetime of the application. As a developer, you often need to store information such as user preferences or application configurations. You must also decide based on characteristics such as access visibility whether you need to involve internal or external memory, or whether you need to deal with more complex, structured data types. Follow this article to learn about the Android data storage APIs, specifically the preferences, SQLite, and internal and external memory APIs. I hope this document will help friends in need; interested friends can come and take a look.