Question

I’m implementing my own Content Provider because I’m gonna synchronize my database with a server. My data is stored in a SQLiteDatabase, and some of my tables have a compound primary key (2 columns, each one a foreign key to another table).

I just started working with Content Providers and I don’t know much how they work, but as I could see googling a bit I need to define the name of the tables and their primary key:

uriMatcher.addURI(PROVIDER_NAME, "books", BOOKS);
uriMatcher.addURI(PROVIDER_NAME, "books/#", BOOK_ID);

As I understand it, if I use the URI …/books/1 it would access the Book with primary key “1”. The thing is, does it work with a compund primary key? If it does, how would the URI be?

Thank you!

Answer 1

I’m implementing my own Content Provider because I’m gonna synchronize my database with a server.

You do not need to use a ContentProvider to synchronize a database with a server.

The thing is, does it work with a compund primary key?

Not readily. Quoting the docs:

Table data should always have a “primary key” column that the provider maintains as a unique numeric value for each row.

You could to add a separate column (typically named _id) that you will use for the ContentProvider as the primary key. If you use an AUTOINCREMENT column, you will not ever have to assign a value yourself, meaning that you can ignore this column in pretty much all respects except where ContentProvider wants an instance Uri.

You are welcome to attempt to avoid this, and use a Uri that looks like content://your.authority.goes.here/table/key1/key2 or something like that. However, it will not work with CursorAdapter and various other places in the framework may assume the numeric ID pattern.