y previous Android article
showed how to store data from Android using a SQLite database. Storing your data in a database is one good way to persist your data, but there's a caveat in Android—databases created in Android are visible only to the application that created them. That is to say, a SQLite database created on Android by one application is usable only by that application, not by other applications.
So, if you need to share data between applications, you need to use the content provider model
as recommended in Android. This article presents the basics of content providers and how you can implement one.
Using a Content Provider
In Android, a content provider is a specialized type of data store that exposes standardized ways to retrieve and manipulate the stored data. Android ships with several useful content providers, as shown in Table 1.
Table 1. Android Content Providers: Here are some of Android's most useful built-in content providers, along with a description of the type of data they're intended to store.
||Browser bookmarks, browser history, etc.
||Missed calls, call details, etc.
||Media files such as audio, video and images
||Device settings and preferences
To query a content provider, you provide a query string in the form of a URI, with an optional specifier for a particular row, using the following syntax:
For example, to retrieve all the bookmarks stored by your web browsers (in Android), you would use the following content URI:
Similarly, to retrieve all the contacts stored by the Contacts application, the URI would look like this:
To retrieve a particular contact, you can specify the URI with a specific ID:
Of course, you can access all this information programmatically as well. The rest of this article walks you through the process.