How to address multiple content providers?

Question

I created two content providers that work on two different tables of the same SQLite database. They share a single instance of SQLiteOpenHelper as described in the post of Ali Serghini. Each content provider is registered in AndroidManifest.xml as follows.

<provider
    android:name=".contentprovider.PostsContentProvider"
    android:authorities="com.example.myapp.provider"
    android:exported="false"
    android:multiprocess="true" >
</provider>
<provider
    android:name=".contentprovider.CommentsContentProvider"
    android:authorities="com.example.myapp.provider"
    android:exported="false"
    android:multiprocess="true" >
</provider>

Each content provider defines the needed content URIs and supplies an UriMatcher.

public class PostsProvider extends BaseContentProvider {

    private static final UriMatcher sUriMatcher = buildUriMatcher();
    private static final int POSTS = 100;
    private static final int POST_ID = 101;

    private static UriMatcher buildUriMatcher() {
        final UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
        final String authority = CustomContract.CONTENT_AUTHORITY;
        matcher.addURI(authority, DatabaseProperties.TABLE_NAME_POSTS, POSTS);
        matcher.addURI(authority, DatabaseProperties.TABLE_NAME_POSTS + "/#", POST_ID);
        return matcher;
    }

...

public class CommentsProvider extends BaseContentProvider {

    protected static final UriMatcher sUriMatcher = buildUriMatcher();
    protected static final int COMMENTS = 200;
    protected static final int COMMENT_ID = 201;

    private static UriMatcher buildUriMatcher() {
        final UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
        final String authority = CustomContract.CONTENT_AUTHORITY;
        matcher.addURI(authority, DatabaseProperties.TABLE_NAME_COMMENTS, COMMENTS);
        matcher.addURI(authority, DatabaseProperties.TABLE_NAME_COMMENTS + "/#", COMMENT_ID);
        return matcher;
    }

When I invoke the content resolver to insert posts, the PostsContentProvider is targeted. When I try to insert comments, however, the content resolver does not refer to the CommentsContentProvider as expected, but calls upon the PostsContentProvider. The result is the following exception which I throw in the PostsContentProvider.

UnsupportedOperationException: Unknown URI: content://com.example.myapp.provider/comments

Is it possible to output all available content URIs currently registered with an content provider?

"I created two content providers that work on two different tables of the same SQLite database" -- why not use one `ContentProvider` that works "on two different tables of the same SQLite database"? That's what the path is for in the `Uri`, to allow you to distinguish between different tables or the like. — CommonsWare, Aug 15 '12 at 21:09
@CommonsWare Because I plan to use a `SyncAdapter` in the future and I heard that a provider's data can only be synced if it is a separate provider. Please correct me if I am wrong. I am happy to read any documentation on that topic. — JJD, Aug 15 '12 at 21:19
Ah, OK. I haven't played with `SyncAdapter` yet. I would be somewhat surprised by the limitation you cite, but I have no knowledge of whether that limitation exists or not. Sorry! — CommonsWare, Aug 15 '12 at 21:22
No offense taken. The `SyncAdapter` is a mysterious thing still to me. I researched quite a while but I am still not sure whether I can [use a `SyncAdapter` to sync "normal" data with a REST backend](http://stackoverflow.com/questions/11906172/synchronize-android-client-and-rest-server). — JJD, Aug 15 '12 at 22:02

score 33 · Accepted Answer · answered Aug 15 '12 at 21:14

33

The android:authorities needs to be unique for each content provider. The documentation is here quoted from doc

The content: scheme identifies the data as belonging to a content provider and the authority (com.example.project.healthcareprovider) identifies the particular provider. The authority therefore must be unique.

answered Aug 15 '12 at 21:14

nandeesh

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I saw this one coming by the time I found this post, but thank you for confirming. Strangely enough, the documentation currently does not mention anymore that the name should be unique? – Martijn de Milliano Feb 19 '13 at 18:26
Ten years later, confirming that the docs still don't mention that the authorities should be unique. However, it does say (in an example) "The authority `com.example.project.healthcareprovider` identifies the provider itself," which taken at face value, suggests that the authority has to be unique, in order to uniquely identify the provider. – LarsH May 05 '23 at 15:52

How to address multiple content providers?

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