Keeps track of "last account used"

This only applies for the main EmailActivity. The compose window still
uses the user-visible setting for "Default account" as the default
account when handling intents like "mailto:" links.

In the future, we should probably just remove that setting, now that we
remember the last account in the reading-email case.

Bug: 4460450
Change-Id: I4b3e7c9e13b7e89320891346383780cd670492ae

src/com/android/email/Preferences.java

@@ -22,6 +22,7 @@ import android.text.TextUtils;
 import android.util.Log;
 
 import com.android.emailcommon.Logging;
+import com.android.emailcommon.provider.Account;
 
 import org.json.JSONArray;
 import org.json.JSONException;
@@ -48,6 +49,7 @@ public class Preferences {
     private static final String TEXT_ZOOM = "textZoom";
     private static final String BACKGROUND_ATTACHMENTS = "backgroundAttachments";
     private static final String TRUSTED_SENDERS = "trustedSenders";
+    private static final String LAST_ACCOUNT_USED = "lastAccountUsed";
 
     public static final int AUTO_ADVANCE_NEWER = 0;
     public static final int AUTO_ADVANCE_OLDER = 1;
@@ -262,6 +264,29 @@ public class Preferences {
         return new JSONArray(set).toString();
     }
 
+    /**
+     * Returns the last used account ID as set by {@link #setLastUsedAccountId}.
+     * The system makes no attempt to automatically track what is considered a "use" - clients
+     * are expected to call {@link #setLastUsedAccountId} manually.
+     *
+     * Note that the last used account may have been deleted in the background so there is also
+     * no guarantee that the account exists.
+     */
+    public long getLastUsedAccountId() {
+        return mSharedPreferences.getLong(LAST_ACCOUNT_USED, Account.NO_ACCOUNT);
+    }
+
+    /**
+     * Sets the specified ID of the last account used. Treated as an opaque ID and does not
+     * validate the value. Value is saved asynchronously.
+     */
+    public void setLastUsedAccountId(long accountId) {
+        mSharedPreferences
+                .edit()
+                .putLong(LAST_ACCOUNT_USED, accountId)
+                .apply();
+    }
+
     public void clear() {
         mSharedPreferences.edit().clear().apply();
     }

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

@@ -206,6 +206,7 @@ abstract class UIControllerBase implements MailboxListFragment.Callback,
         if (mNfcHandler != null) {
             mNfcHandler.onAccountChanged();  // workaround for email not set on initial load
         }
+        Preferences.getPreferences(mActivity).setLastUsedAccountId(getUIAccountId());
     }
 
     /**
@@ -556,6 +557,7 @@ abstract class UIControllerBase implements MailboxListFragment.Callback,
         if (mNfcHandler != null) {
             mNfcHandler.onAccountChanged();
         }
+        Preferences.getPreferences(mActivity).setLastUsedAccountId(accountId);
     }
 
     /**

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

@@ -30,6 +30,7 @@ import android.view.View;
 import android.view.ViewGroup.LayoutParams;
 
 import com.android.email.Email;
+import com.android.email.Preferences;
 import com.android.email.R;
 import com.android.email.activity.setup.AccountSettings;
 import com.android.email.activity.setup.AccountSetupBasics;
@@ -314,8 +315,18 @@ public class Welcome extends Activity {
             }
         } else {
             // Neither an accountID or a UUID is specified.
-            // Use the default, without showing the "account removed?" toast.
-            accountId = Account.getDefaultAccountId(context);
+            // Use the last account used, falling back to the default.
+            long lastUsedId = Preferences.getPreferences(context).getLastUsedAccountId();
+            if (lastUsedId != Account.NO_ACCOUNT) {
+                if (!Account.isValidId(context, lastUsedId)) {
+                    // The last account that was used has since been deleted.
+                    lastUsedId = Account.NO_ACCOUNT;
+                    Preferences.getPreferences(context).setLastUsedAccountId(Account.NO_ACCOUNT);
+                }
+            }
+            accountId = (lastUsedId == Account.NO_ACCOUNT)
+                    ? Account.getDefaultAccountId(context)
+                    : lastUsedId;
         }
         if (accountId != Account.NO_ACCOUNT) {
             // Okay, the given account is valid.