Best practices for joining tables and notifying ContentObservers in Android ContentProvider

Question

I have a ContentProvider which handles all the data insertion and retrieval related to my application, I'm following the pattern suggested by Virgil Dobjanschi on Google I/O. I am using the first pattern.

My problem is that I have a logical entity that was represented by multiple tables in the database.

For example, I have an Articles table and an ArticleExtras table. Articles represents the article itself, while ArticleExtras represents addtional information about certain Article, like number of comments.

I used CursorAdapter in the UI to display the Article title and the number of comments of that Article in one row of ListView.

To implement that, I added a left outer join ArticleExtras on statement in my ContentProvider query method for Article table, in order for CursorAdapter to get ArticleExtras along with the Article itself.

When new Articles are fetched from the web, I insert it into the database via ContentProvider, and then the CursorAdapter got notified and update the UI, this part worked as expected.

But when I fetched the number of comments (ArticleExtras), I want the same CursorAdapter, which is watching for changes in the content://com.myapp.content/Articles, to be notified, too, so I can update my row in the ListView.

My current implementation is like this: After inserting ArticleExtras into the database, I start a new query to check if Articles table has any rows that is related to the ArticleExtras I just inserted. If so I'll make a new uri for that Article( for example: content://com.myapp.cotent/Articles/123), and call getContext().getContentResolver().notifyChange(uri, null), so the corresponding CursorAdapter that is watching for changes of this Article will get notified.

Is the approach correct, or is there any better way to implement what I want?

Answer 1

Checkout ContactsProvider2, in it they set the notification uri to the AUTHORITY_URI which appears to be a catch all for the other URIs in the provider. I had the same probem and I have tried this myself for a provider with multiple tables and joins on those tables, and it works fine.