Show Log Out instead of Login in menu when logged in.

By asynchronously caching the login status (async because we are asking
the AccountManager, not being we are asking the server) in onResume()
and using that in onPrepareOptionsMenu().
However, this will incorrectly show the user as logged in if they
change their password on the web server - clients have no way
to check that the api_key is still valid, even when using the api_key
to submit a classification:
zooniverse/Galaxy-Zoo#184

This fixes this issue:
#18

app/src/main/java/com/murrayc/galaxyzoo/app/ListFragment.java

@@ -147,7 +147,6 @@ public View onCreateView(final LayoutInflater inflater, final ViewGroup containe
                              final Bundle savedInstanceState) {
         // We would only call the base class's onCreateView if we wanted the default layout:
         // super.onCreateView(inflater, container, savedInstanceState);
-
         mRootView = inflater.inflate(R.layout.fragment_list, container, false);
         assert mRootView != null;
 

app/src/main/java/com/murrayc/galaxyzoo/app/LoginUtils.java

@@ -24,13 +24,15 @@
 import android.accounts.AccountManagerFuture;
 import android.accounts.AuthenticatorException;
 import android.accounts.OperationCanceledException;
+import android.app.Activity;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.os.AsyncTask;
 import android.os.Build;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
+import android.support.v4.app.FragmentActivity;
 import android.text.TextUtils;
 import android.util.JsonReader;
 
@@ -69,6 +71,17 @@ public final class LoginUtils {
      */
     public static boolean getLoggedIn(final Context context) {
         final LoginDetails loginDetails = getAccountLoginDetails(context);
+        return getLoggedIn(loginDetails);
+    }
+
+    /**
+     * This is a just a utility method that examines the LoginDetails.
+     * Unlike getLoggedIn(Context), this can be called from any thread.
+     *
+     * @param loginDetails
+     * @return
+     */
+    public static boolean getLoggedIn(final LoginDetails loginDetails) {
         if (loginDetails == null) {
             return false;
         }
@@ -184,6 +197,30 @@ public static LoginDetails getAccountLoginDetails(final Context context) {
         }
     }
 
+    public static void logOut(final ZooFragment fragment) {
+        final Activity activity = fragment.getActivity();
+        final AccountRemoveTask task = new AccountRemoveTask(activity) {
+            @Override
+            protected void onPostExecute(final Void result) {
+                super.onPostExecute(result);
+
+                //Make sure that the currently-shown menu will update:
+                fragment.setLoggedIn(false);
+
+                //TODO: This doesn't actually seem to cause the (various) child fragments'
+                //onPrepareOptionsMenu() methods to be called. Maybe it doesn't work with
+                //nested child fragments.
+                if (activity instanceof FragmentActivity) {
+                    final FragmentActivity fragmentActivity = (FragmentActivity) activity;
+                    fragmentActivity.supportInvalidateOptionsMenu();
+                } else {
+                    activity.invalidateOptionsMenu();
+                }
+            }
+        };
+        task.execute();
+    }
+
     /**
      * Add the anonymous Account.
      *
@@ -436,6 +473,48 @@ protected void onCancelled() {
         }
     }
 
+    /** Run this to log out.
+     */
+    private static class AccountRemoveTask extends AsyncTask<Void, Void, Void> {
+
+        private final WeakReference<Context> contextReference;
+
+        AccountRemoveTask(final Context context) {
+            this.contextReference = new WeakReference<>(context);
+        }
+
+        @Override
+        protected Void doInBackground(final Void... params) {
+
+            if (contextReference == null) {
+                return null;
+            }
+
+            final Context context = contextReference.get();
+            if (context == null) {
+                return null;
+            }
+
+            LoginUtils.LoginDetails loginDetails = LoginUtils.getAccountLoginDetails(context);
+            if(!LoginUtils.getLoggedIn(loginDetails)) {
+                return null;
+            }
+
+            final String accountName = loginDetails.name;
+            if (TextUtils.isEmpty(accountName)) {
+                return null;
+            }
+
+            final AccountManager accountManager = AccountManager.get(context);
+            LoginUtils.removeAccount(context, accountName);
+
+            LoginUtils.addAnonymousAccount(context);
+
+            return null;
+        }
+    }
+
+
     public static class LoginResult {
         private final boolean success;
         private final String name;
@@ -459,4 +538,4 @@ public String getName() {
             return name;
         }
     }
-}
+}

app/src/main/java/com/murrayc/galaxyzoo/app/ZooFragment.java

@@ -21,19 +21,54 @@
 
 import android.app.Activity;
 import android.content.Intent;
+import android.os.Bundle;
 import android.support.v4.app.Fragment;
 import android.support.v7.app.AlertDialog;
 import android.text.SpannableStringBuilder;
 import android.text.method.LinkMovementMethod;
 import android.view.LayoutInflater;
+import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
+import android.view.ViewGroup;
 import android.widget.TextView;
 
 /**
  * Created by murrayc on 8/7/14.
  */
 public class ZooFragment extends Fragment {
+    private boolean loggedIn = false;
+
+    @Override
+    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+        return super.onCreateView(inflater, container, savedInstanceState);
+    }
+
+    @Override
+    public void onResume() {
+        super.onResume();
+
+        cacheLoggedInStatus();
+    }
+
+    /** Asynchronously cache the log in status in loggedIn.
+     * Derived classes can call this in their onCreateView.
+     **/
+    protected void cacheLoggedInStatus() {
+        final LoginUtils.GetExistingLogin task = new LoginUtils.GetExistingLogin(getActivity()) {
+            @Override
+            protected void onPostExecute(final LoginUtils.LoginDetails loginDetails) {
+                super.onPostExecute(loginDetails);
+
+                ZooFragment.this.setLoggedIn(LoginUtils.getLoggedIn(loginDetails));
+            }
+        };
+        task.execute();
+    }
+
+    public void setLoggedIn(boolean loggedIn) {
+        this.loggedIn = loggedIn;
+    }
 
     @Override
     public boolean onOptionsItemSelected(final MenuItem item) {
@@ -42,6 +77,9 @@ public boolean onOptionsItemSelected(final MenuItem item) {
             case R.id.option_menu_item_login:
                 requestLogin();
                 return true;
+            case R.id.option_menu_item_logout:
+                requestLogout();
+                return true;
             case R.id.option_menu_item_about:
                 showAbout();
                 return true;
@@ -53,6 +91,25 @@ public boolean onOptionsItemSelected(final MenuItem item) {
         }
     }
 
+    @Override
+    public void onPrepareOptionsMenu(final Menu menu) {
+        super.onPrepareOptionsMenu(menu);
+
+        //Before the menu item is displayed,
+        //show either "Log in" or "Log out":
+        //This depends on cacheLoggedInStatus() having been called in onResume().
+        final MenuItem itemLogin = menu.findItem(R.id.option_menu_item_login);
+        final MenuItem itemLogout = menu.findItem(R.id.option_menu_item_logout);
+
+        if ((itemLogin == null) || (itemLogout == null)) {
+            Log.error("onPrepareOptionsMenu(): Could not find menu items.");
+            return;
+        }
+
+        itemLogin.setVisible(!loggedIn);
+        itemLogout.setVisible(loggedIn);
+    }
+
     /*
     void requestMoreItems() {
         final Activity activity = getActivity();
@@ -78,6 +135,10 @@ private void requestLogin() {
         startActivity(intent);
     }
 
+    private void requestLogout() {
+        LoginUtils.logOut(this);
+    }
+
     private void showAbout() {
         final Activity activity = getActivity();
         final AlertDialog.Builder builder = new AlertDialog.Builder(activity);

app/src/main/res/menu/actionbar_menu_item_common.xml

@@ -5,6 +5,10 @@
         android:id="@+id/option_menu_item_login"
         android:title="@string/action_login"
         android:orderInCategory="7" />
+    <item
+        android:id="@+id/option_menu_item_logout"
+        android:title="@string/action_logout"
+        android:orderInCategory="7" />
     <item
         android:id="@+id/option_menu_item_list"
         android:title="@string/action_list"

app/src/main/res/menu/actionbar_menu_list.xml

@@ -6,6 +6,9 @@
     <item
         android:id="@+id/option_menu_item_login"
         android:title="@string/action_login" />
+    <item
+        android:id="@+id/option_menu_item_logout"
+        android:title="@string/action_logout" />
     <!-- The More action is only useful for debugging:
     <item
         android:id="@+id/option_menu_item_more"

app/src/main/res/values/strings.xml

@@ -38,6 +38,9 @@
     <!-- An action. Shown on a button or menu item. -->
     <string name="action_login">Login</string>
 
+    <!-- An action. Shown on a button or menu item. -->
+    <string name="action_logout">Log out</string>
+
     <!-- A checkable action with two states. It is either a favorite or not. Shown on a button or menu item. -->
     <string name="action_favorite">Favorite</string>