NFC zero-click sharing for Email.

This shares the e-mail address of the currently shown account
over P2P NFC links. Note that the currently set account must
be updated actively, because the callback to create the message
comes from one of the NFC threads, which don't have permissions
to retrieve the account and the correspondig e-mail address.

Change-Id: I12e48a3787d469179e7ca074429106ed24e3a212

AndroidManifest.xml

@@ -53,6 +53,9 @@
     <uses-permission
         android:name="android.permission.READ_CONTACTS"/>
 
+    <uses-permission
+        android:name="android.permission.NFC"/>
+
     <!-- Only required if a store implements push mail and needs to keep network open -->
     <uses-permission
         android:name="android.permission.WAKE_LOCK"/>

src/com/android/email/activity/NfcHandler.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.email.activity;
+
+import com.android.emailcommon.provider.Account;
+
+import android.app.Activity;
+import android.content.Context;
+import android.nfc.NdefMessage;
+import android.nfc.NdefRecord;
+import android.nfc.NfcAdapter;
+import android.text.TextUtils;
+import android.util.Log;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLEncoder;
+
+/**
+  * This class implements sharing the e-mail address of the
+  * active account to another device using NFC. NFC sharing is only
+  * enabled when the activity is in the foreground and resumed.
+  * When an NFC link is established, {@link #createMessage}
+  * will be called to create the data to be sent over the link,
+  * which is a vCard in this case.
+  */
+public class NfcHandler implements NfcAdapter.NdefPushCallback {
+    private NfcAdapter mNfcAdapter;
+    private UIControllerBase mUiController;
+    private Activity mActivity;
+    private String mCurrentEmail;
+    private static final String TAG = "ContactsNfcHandler";
+
+    public NfcHandler(UIControllerBase controller, Activity
+            activity) {
+        mUiController = controller;
+        mActivity = activity;
+        mNfcAdapter = NfcAdapter.getDefaultAdapter(mActivity);
+    }
+
+    public void onAccountChanged() {
+        if (mUiController.isActualAccountSelected()) {
+            final long accountId = mUiController.getActualAccountId();
+            final Account account = Account.restoreAccountWithId(
+                    mActivity, accountId);
+            mCurrentEmail = account.mEmailAddress;
+        } else {
+            mCurrentEmail = null;
+        }
+
+    }
+
+    public void onPause() {
+        if (mNfcAdapter != null) {
+            mNfcAdapter.disableForegroundNdefPush(
+                    mActivity);
+        }
+    }
+
+    public void onResume() {
+        if (mNfcAdapter != null) {
+            mNfcAdapter.enableForegroundNdefPush(
+                    mActivity, this);
+            onAccountChanged(); // Fetch current account
+        }
+    }
+
+    private static NdefMessage buildMailtoNdef(String address) {
+        if (TextUtils.isEmpty(address)) {
+            return null;
+        }
+        byte[] accountBytes;
+        try {
+            accountBytes = URLEncoder.encode(address, "UTF-8")
+                    .getBytes("UTF-8");
+        } catch (UnsupportedEncodingException e) {
+            return null;
+        }
+        byte[] recordBytes = new byte[accountBytes.length + 1];
+        recordBytes[0] = 0x06; // NDEF mailto: prefix
+        System.arraycopy(accountBytes, 0, recordBytes, 1, accountBytes.length);
+        NdefRecord mailto = new NdefRecord(NdefRecord.TNF_WELL_KNOWN, NdefRecord.RTD_URI,
+                new byte[0], recordBytes);
+        return new NdefMessage(new NdefRecord[] { mailto });
+    }
+
+    @Override
+    public NdefMessage createMessage() {
+        if (mCurrentEmail != null) {
+            return buildMailtoNdef(mCurrentEmail);
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public void onMessagePushed() {
+    }
+}

src/com/android/email/activity/UIControllerBase.java

@@ -93,6 +93,12 @@ abstract class UIControllerBase implements MailboxListFragment.Callback,
      */
     private final List<Fragment> mRemovedFragments = new LinkedList<Fragment>();
 
+    /**
+     * The NfcHandler implements Near Field Communication sharing features
+     * whenever the activity is in the foreground.
+     */
+    private NfcHandler mNfcHandler;
+
     /**
      * The active context for the current MessageList.
      * In some UI layouts such as the one-pane view, the message list may not be visible, but is
@@ -143,6 +149,7 @@ abstract class UIControllerBase implements MailboxListFragment.Callback,
         if (DEBUG_FRAGMENTS) {
             FragmentManager.enableDebugLogging(true);
         }
+        mNfcHandler = new NfcHandler(this, activity);
     }
 
     /**
@@ -196,6 +203,7 @@ abstract class UIControllerBase implements MailboxListFragment.Callback,
             Log.d(Logging.LOG_TAG, this + " onActivityResume");
         }
         refreshActionBar();
+        mNfcHandler.onResume();
     }
 
     /**
@@ -205,6 +213,7 @@ abstract class UIControllerBase implements MailboxListFragment.Callback,
         if (Logging.DEBUG_LIFECYCLE && Email.DEBUG) {
             Log.d(Logging.LOG_TAG, this + " onActivityPause");
         }
+        mNfcHandler.onPause();
     }
 
     /**
@@ -529,7 +538,6 @@ abstract class UIControllerBase implements MailboxListFragment.Callback,
             // Do nothing if the account is already selected.  Not even going back to the inbox.
             return;
         }
-
         if (accountId == Account.ACCOUNT_ID_COMBINED_VIEW) {
             openMailbox(accountId, Mailbox.QUERY_ALL_INBOXES);
         } else {
@@ -541,11 +549,11 @@ abstract class UIControllerBase implements MailboxListFragment.Callback,
                         + " to Welcome...");
                 Welcome.actionOpenAccountInbox(mActivity, accountId);
                 mActivity.finish();
-                return;
             } else {
                 openMailbox(accountId, inboxId);
             }
         }
+        mNfcHandler.onAccountChanged();
     }
 
     /**