Retrieving Details for a Contact

This lesson shows how to retrieve detail data for a contact, such as email addresses, phone numbers, and so forth. It's the details that users are looking for when they retrieve a contact. You can give them all the details for a contact, or only display details of a particular type, such as email addresses.

The steps in this lesson assume that you already have a ContactsContract.Contacts row for a contact the user has picked. The Retrieving Contact Names lesson shows how to retrieve a list of contacts.

Retrieve All Details for a Contact

To retrieve all the details for a contact, search the ContactsContract.Data table for any rows that contain the contact's LOOKUP_KEY. This column is available in the ContactsContract.Data table, because the Contacts Provider makes an implicit join between the ContactsContract.Contacts table and the ContactsContract.Data table. The LOOKUP_KEY column is described in more detail in the Retrieving Contact Names lesson.

Note: Retrieving all the details for a contact reduces the performance of a device, because it needs to retrieve all of the columns in the ContactsContract.Data table. Consider the performance impact before you use this technique.

Request permissions

To read from the Contacts Provider, your app must have READ_CONTACTS permission. To request this permission, add the following child element of <manifest> to your manifest file:

    <uses-permission android:name="android.permission.READ_CONTACTS" />

Set up a projection

Depending on the data type a row contains, it may use only a few columns or many. In addition, the data is in different columns depending on the data type. To ensure you get all the possible columns for all possible data types, you need to add all the column names to your projection. Always retrieve Data._ID if you're binding the result Cursor to a ListView; otherwise, the binding won't work. Also retrieve Data.MIMETYPE so you can identify the data type of each row you retrieve. For example:

    private static final String PROJECTION =
            {
                Data._ID,
                Data.MIMETYPE,
                Data.DATA1,
                Data.DATA2,
                Data.DATA3,
                Data.DATA4,
                Data.DATA5,
                Data.DATA6,
                Data.DATA7,
                Data.DATA8,
                Data.DATA9,
                Data.DATA10,
                Data.DATA11,
                Data.DATA12,
                Data.DATA13,
                Data.DATA14,
                Data.DATA15
            };

This projection retrieves all the columns for a row in the ContactsContract.Data table, using the column names defined in the ContactsContract.Data class.

Optionally, you can also use any other column constants defined in or inherited by the ContactsContract.Data class. Notice, however, that the columns SYNC1 through SYNC4 are meant to be used by sync adapters, so their data is not useful.

Define the selection criteria

Define a constant for your selection clause, an array to hold selection arguments, and a variable to hold the selection value. Use the Contacts.LOOKUP_KEY column to find the contact. For example:

    // Defines the selection clause
    private static final String SELECTION = Data.LOOKUP_KEY + " = ?";
    // Defines the array to hold the search criteria
    private String[] mSelectionArgs = { "" };
    /*
     * Defines a variable to contain the selection value. Once you
     * have the Cursor from the Contacts table, and you've selected
     * the desired row, move the row's LOOKUP_KEY value into this
     * variable.
     */
    private String mLookupKey;

Using "?" as a placeholder in your selection text expression ensures that the resulting search is generated by binding rather than SQL compilation. This approach eliminates the possibility of malicious SQL injection.

Define the sort order

Define the sort order you want in the resulting Cursor. To keep all rows for a particular data type together, sort by Data.MIMETYPE. This query argument groups all email rows together, all phone rows together, and so forth. For example:

    /*
     * Defines a string that specifies a sort order of MIME type
     */
    private static final String SORT_ORDER = Data.MIMETYPE;

Note: Some data types don't use a subtype, so you can't sort on subtype. Instead, you have to iterate through the returned Cursor, determine the data type of the current row, and store data for rows that use a subtype. When you finish reading the cursor, you can then sort each data type by subtype and display the results.

Initialize the Loader

Always do retrievals from the Contacts Provider (and all other content providers) in a background thread. Use the Loader framework defined by the LoaderManager class and the LoaderManager.LoaderCallbacks interface to do background retrievals.

When you're ready to retrieve the rows, initialize the loader framework by calling initLoader(). Pass an integer identifier to the method; this identifier is passed to LoaderManager.LoaderCallbacks methods. The identifier helps you use multiple loaders in an app by allowing you to differentiate between them.

The following snippet shows how to initialize the loader framework:

public class DetailsFragment extends Fragment implements
        LoaderManager.LoaderCallbacks<Cursor> {
    ...
    // Defines a constant that identifies the loader
    DETAILS_QUERY_ID = 0;
    ...
    /*
     * Invoked when the parent Activity is instantiated
     * and the Fragment's UI is ready. Put final initialization
     * steps here.
     */
    @Override
    onActivityCreated(Bundle savedInstanceState) {
        ...
        // Initializes the loader framework
        getLoaderManager().initLoader(DETAILS_QUERY_ID, null, this);

Implement onCreateLoader()

Implement the onCreateLoader() method, which is called by the loader framework immediately after you call initLoader(). Return a CursorLoader from this method. Since you're searching the ContactsContract.Data table, use the constant Data.CONTENT_URI as the content URI. For example:

    @Override
    public Loader<Cursor> onCreateLoader(int loaderId, Bundle args) {
        // Choose the proper action
        switch (loaderId) {
            case DETAILS_QUERY_ID:
            // Assigns the selection parameter
            mSelectionArgs[0] = mLookupKey;
            // Starts the query
            CursorLoader mLoader =
                    new CursorLoader(
                            getActivity(),
                            Data.CONTENT_URI,
                            PROJECTION,
                            SELECTION,
                            mSelectionArgs,
                            SORT_ORDER
                    );
            ...
    }

Implement onLoadFinished() and onLoaderReset()

Implement the onLoadFinished() method. The loader framework calls onLoadFinished() when the Contacts Provider returns the results of the query. For example:

    public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
        switch (loader.getId()) {
            case DETAILS_QUERY_ID:
                    /*
                     * Process the resulting Cursor here.
                     */
                }
                break;
            ...
        }
    }

The method onLoaderReset() is invoked when the loader framework detects that the data backing the result Cursor has changed. At this point, remove any existing references to the Cursor by setting them to null. If you don't, the loader framework won't destroy the old Cursor, and you'll get a memory leak. For example:

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        switch (loader.getId()) {
            case DETAILS_QUERY_ID:
                /*
                 * If you have current references to the Cursor,
                 * remove them here.
                 */
                }
                break;
    }

Retrieve Specific Details for a Contact

Retrieving a specific data type for a contact, such as all the emails, follows the same pattern as retrieving all details. These are the only changes you need to make to the code listed in Retrieve All Details for a Contact:

Projection

Modify your projection to retrieve the columns that are specific to the data type. Also modify the projection to use the column name constants defined in the ContactsContract.CommonDataKinds subclass corresponding to the data type.

Selection

Modify the selection text to search for the MIMETYPE value that's specific to your data type.

Sort order

Since you're only selecting a single detail type, don't group the returned Cursor by Data.MIMETYPE.

These modifications are described in the following sections.

Define a projection

Define the columns you want to retrieve, using the column name constants in the subclass of ContactsContract.CommonDataKinds for the data type. If you plan to bind your Cursor to a ListView, be sure to retrieve the _ID column. For example, to retrieve email data, define the following projection:

    private static final String[] PROJECTION =
            {
                Email._ID,
                Email.ADDRESS,
                Email.TYPE,
                Email.LABEL
            };

Notice that this projection uses the column names defined in the class ContactsContract.CommonDataKinds.Email, instead of the column names defined in the class ContactsContract.Data. Using the email-specific column names makes the code more readable.

In the projection, you can also use any of the other columns defined in the ContactsContract.CommonDataKinds subclass.

Define selection criteria

Define a search text expression that retrieves rows for a specific contact's LOOKUP_KEY and the Data.MIMETYPE of the details you want. Enclose the MIMETYPE value in single quotes by concatenating a "'" (single-quote) character to the start and end of the constant; otherwise, the provider interprets the constant as a variable name rather than as a string value. You don't need to use a placeholder for this value, because you're using a constant rather than a user-supplied value. For example:

    /*
     * Defines the selection clause. Search for a lookup key
     * and the Email MIME type
     */
    private static final String SELECTION =
            Data.LOOKUP_KEY + " = ?" +
            " AND " +
            Data.MIMETYPE + " = " +
            "'" + Email.CONTENT_ITEM_TYPE + "'";
    // Defines the array to hold the search criteria
    private String[] mSelectionArgs = { "" };

Define a sort order

Define a sort order for the returned Cursor. Since you're retrieving a specific data type, omit the sort on MIMETYPE. Instead, if the type of detail data you're searching includes a subtype, sort on it. For example, for email data you can sort on Email.TYPE:

    private static final String SORT_ORDER = Email.TYPE + " ASC ";