noticias electronica: blog The Gmail Public Labels API

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[This post is by Nadav Aharony, a product manager on the Android team — Tim Bray]

We're rolling out new developer features for the Gmail Android app: It now includes a public ContentProvider that you can use to retrieve label data. You can use this to access up-to-date unread counts for specific accounts' inboxes and labels.

To use the API, the Gmail app needs to be at version 2.3.6 or higher on Froyo or Gingerbread; 4.0.5 or higher on Honeycomb and ICS. Before using it, be sure you first check the Gmail app version; we've provided a handy GmailContract.canReadLabels(Context) method to help with this. Your app will need the com.google.android.gm.permission.READ_CONTENT_PROVIDER permission.

Finding the Gmail accounts set up on the device

The Labels API needs a valid Gmail account to build a query for per-label information. Assuming the GET_ACCOUNTS permission, the AccountManager can be used to fetch this information:

// Get the account list, and pick the first one  final String ACCOUNT_TYPE_GOOGLE = 'com.google';  final String[] FEATURES_MAIL = {          'service_mail'  };  AccountManager.get(this).getAccountsByTypeAndFeatures(ACCOUNT_TYPE_GOOGLE, FEATURES_MAIL,          new AccountManagerCallback() {              @Override              public void run(AccountManagerFuture future) {                  Account[] accounts = null;                  try {                      accounts = future.getResult();                      if (accounts != null && accounts.length > 0) {                          String selectedAccount = accounts[0].name;                          queryLabels(selectedAccount);                      }                    } catch (OperationCanceledException oce) {                      // TODO: handle exception                  } catch (IOException ioe) {                      // TODO: handle exception                  } catch (AuthenticatorException ae) {                      // TODO: handle exception                  }              }          }, null /* handler */);

Getting and accessing existing labels

Once you've got the email account, you can get a ContentProvider URI to query against. We've provided a simple support class called GmailContract.java for constructing the URI and defining the columns and relevant constants.

You can access any label, predefined or user-defined. The predefined labels include (you have to use symbolic constants rather than these strings, see below):

Priority Inbox
Starred
Chats
Sent
Drafts
All mail
Spam
Trash

To obtain a Cursor with information for all labels in an account, your app can either query this URI directly or use a CursorLoader. Here's an example:

Cursor c =       getContentResolver().query(GmailContract.Labels.getLabelsUri(selectedAccount),           null, null, null, null);

You can query and watch for changes on a single label by storing the URI value in the GmailContract.Labels.URI column from the cursor data.

The NAME value for pre-defined labels can vary by locale, so don't use GmailContract.Labels.NAME. Instead, identify pre-defined labels like Inbox, Sent or Drafts using the String value in the GmailContract.Labels.CANONICAL_NAME column. Here's an example:

// loop through the cursor and find the Inbox  if (c != null) {      final String inboxCanonicalName = GmailContract.Labels.LabelCanonicalName.CANONICAL_NAME_INBOX;      final int canonicalNameIndex = c.getColumnIndexOrThrow(GmailContract.Labels.CANONICAL_NAME);      while (c.moveToNext()) {          if (inboxCanonicalName.equals(c.getString(canonicalNameIndex))) {              // this row corresponds to the Inbox          }      }  }

If you choose to use a CursorLoader, it will keep the label counts up to date as they change over time.

Sample App

You can find a sample app that makes use of the new API here. The app provides a basic readout of label and message-count information.

People care about their incoming mail; we're looking forward to seeing what you do with access to this information. We're also open to suggestions as to how to improve and extend this new API.