Content Providers

Content providers are used to share data between applications -- e.g., your contacts. We use content providers in the MyRuns3 app not to share the exercise database between application but to manage data inside a single application. We do this because content providers offer hooks that allow sometimes costly access to a database (for example, in terms of the latency cost of reading or writing to the database) to be hidden. This is important. Imagine (extreme example) it takes 1 second to write to the database (you have a lot of data) and that the processing is done inside the UI thread? That would be terrible the user would see a UI that stalls and starts. To get around this content providers allow the user to interact with loaders. In this case a request to insert into the data base happens in a different thread to the UI thread. As a result, control is immediately returned to the UI thread -- the user is happy -- and when the insert in complete, a callback syncs the system up. These threads are hidden from the user and supported in a transparent manner using loaders (the loader manager to be specific) and content providers.

The use of content providers adds another component to our three layer model: content providers -- a wrapper around the database. The cool thing about implementing content providers in MyRuns3 is that we have a new tool in our Android toolkit. And as we will see it is simple to -- if we ever wanted to do this - share data with other distinct applications.

In the following we discuss content providers through a cool little app called notes. Again, we borrow is app from Lars Vogel. Thanks Lars.

Until I add more notes please review: * Android SQLite Database and ContentProvider Tutorial

I suggest you download the notes app and play with it, look at the code. This servers as a framework to implement MyRuns3.

What this lecture will teach you

• Content Providers
• Content Resolvers
• Cursor Loaders
• Loaders

Demo projects

The demo code used in this lecture include:

• Simple use of the camera tododemo.zip. This demo code is taken from Lars Voglel's tutorial on SQLite and slightly modified to include the delate all option.

Resources

Some excellent references.

• Android SQLite Database and ContentProvider Tutorial
• Android developers sqlite. Contains the SQLite database management classes that an application would use to manage its own private database.
• SQLiteOpenHelper a helper class to manage database creation and version management.
• Course book section on SQLite Databases page 453
• SQLite Tutorial