There are several ways to do this, shown below.

As a friendly warning, be careful and up-front to the user when dealing with account, profile, and contact data. If you misuse a user's email address or other personal information, bad things can happen.

Method A: Use AccountManager (API level 5+)

You can use AccountManager.getAccounts or AccountManager.getAccountsByType to get a list of all account names on the device. Fortunately, for certain account types (including com.google), the account names are email addresses. Example snippet below.

Pattern emailPattern = Patterns.EMAIL_ADDRESS; // API level 8+Account[] accounts = AccountManager.get(context).getAccounts();for (Account account : accounts) {    if (emailPattern.matcher(account.name).matches()) {        String possibleEmail = account.name;        ...    }}

Note that this requires the GET_ACCOUNTS permission:

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

More on using AccountManager can be found at the Contact Manager sample code in the SDK.

Method B: Use ContactsContract.Profile (API level 14+)

As of Android 4.0 (Ice Cream Sandwich), you can get the user's email addresses by accessing their profile. Accessing the user profile is a bit heavyweight as it requires two permissions (more on that below), but email addresses are fairly sensitive pieces of data, so this is the price of admission.

Below is a full example that uses a CursorLoader to retrieve profile data rows containing email addresses.

public class ExampleActivity extends Activity implements LoaderManager.LoaderCallbacks<Cursor> {    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        getLoaderManager().initLoader(0, null, this);    }    @Override    public Loader<Cursor> onCreateLoader(int id, Bundle arguments) {        return new CursorLoader(this,                // Retrieve data rows for the device user's 'profile' contact.                Uri.withAppendedPath(                        ContactsContract.Profile.CONTENT_URI,                        ContactsContract.Contacts.Data.CONTENT_DIRECTORY),                ProfileQuery.PROJECTION,                // Select only email addresses.                ContactsContract.Contacts.Data.MIMETYPE + " = ?",                new String[]{ContactsContract.CommonDataKinds.Email.CONTENT_ITEM_TYPE},                // Show primary email addresses first. Note that there won't be                // a primary email address if the user hasn't specified one.                ContactsContract.Contacts.Data.IS_PRIMARY + " DESC");    }    @Override    public void onLoadFinished(Loader<Cursor> cursorLoader, Cursor cursor) {        List<String> emails = new ArrayList<String>();        cursor.moveToFirst();        while (!cursor.isAfterLast()) {            emails.add(cursor.getString(ProfileQuery.ADDRESS));            // Potentially filter on ProfileQuery.IS_PRIMARY            cursor.moveToNext();        }        ...    }    @Override    public void onLoaderReset(Loader<Cursor> cursorLoader) {    }    private interface ProfileQuery {        String[] PROJECTION = {                ContactsContract.CommonDataKinds.Email.ADDRESS,                ContactsContract.CommonDataKinds.Email.IS_PRIMARY,        };        int ADDRESS = 0;        int IS_PRIMARY = 1;    }}

This requires both the READ_PROFILE and READ_CONTACTS permissions:

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

This could be useful to others:

Using AccountPicker to get user's email address without any global permissions, and allowing the user to be aware and authorize or cancel the process.

I would use Android's AccountPicker, introduced in ICS.

Intent googlePicker = AccountPicker.newChooseAccountIntent(null, null, new String[]{GoogleAuthUtil.GOOGLE_ACCOUNT_TYPE}, true, null, null, null, null);startActivityForResult(googlePicker, REQUEST_CODE);

And then wait for the result:

protected void onActivityResult(final int requestCode, final int resultCode,                                final Intent data) {    if (requestCode == REQUEST_CODE && resultCode == RESULT_OK) {        String accountName = data.getStringExtra(AccountManager.KEY_ACCOUNT_NAME);    }}