Add RosterLoadedListener

smack-im/src/main/java/org/jivesoftware/smack/roster/Roster.java

@@ -134,6 +134,11 @@ public class Roster extends Manager {
     private final Set<RosterListener> rosterListeners = new LinkedHashSet<>();
     private final Map<String, Map<String, Presence>> presenceMap = new ConcurrentHashMap<String, Map<String, Presence>>();
 
+    /**
+     * Listeners called when the Roster was loaded.
+     */
+    private final Set<RosterLoadedListener> rosterLoadedListeners = new LinkedHashSet<>();
+
     /**
      * Mutually exclude roster listener invocation and changing the {@link entries} map. Also used
      * to synchronize access to either the roster listeners or the entries map.
@@ -387,6 +392,34 @@ public class Roster extends Manager {
         }
     }
 
+    /**
+     * Add a roster loaded listener.
+     *
+     * @param rosterLoadedListener the listener to add.
+     * @return true if the listener was not already added.
+     * @see RosterLoadedListener
+     * @since 4.1
+     */
+    public boolean addRosterLoadedListener(RosterLoadedListener rosterLoadedListener) {
+        synchronized (rosterLoadedListener) {
+            return rosterLoadedListeners.add(rosterLoadedListener);
+        }
+    }
+
+    /**
+     * Remove a roster loaded listener.
+     *
+     * @param rosterLoadedListener the listener to remove.
+     * @return true if the listener was active and got removed.
+     * @see RosterLoadedListener
+     * @since 4.1
+     */
+    public boolean removeRosterLoadedListener(RosterLoadedListener rosterLoadedListener) {
+        synchronized (rosterLoadedListener) {
+            return rosterLoadedListeners.remove(rosterLoadedListener);
+        }
+    }
+
     /**
      * Creates a new group.<p>
      * <p/>
@@ -1309,6 +1342,22 @@ public class Roster extends Manager {
             }
             // Fire event for roster listeners.
             fireRosterChangedEvent(addedEntries, updatedEntries, deletedEntries);
+
+            // Call the roster loaded listeners after the roster events have been fired. This is
+            // imporant because the user may call getEntriesAndAddListener() in onRosterLoaded(),
+            // and if the order would be the other way around, the roster listener added by
+            // getEntriesAndAddListener() would be invoked with information that was already
+            // available at the time getEntriesAndAddListenr() was called.
+            try {
+                synchronized (rosterLoadedListeners) {
+                    for (RosterLoadedListener rosterLoadedListener : rosterLoadedListeners) {
+                        rosterLoadedListener.onRosterLoaded(Roster.this);
+                    }
+                }
+            }
+            catch (Exception e) {
+                LOGGER.log(Level.WARNING, "RosterLoadedListener threw exception", e);
+            }
         }
     }
 

smack-im/src/main/java/org/jivesoftware/smack/roster/RosterLoadedListener.java

@@ -0,0 +1,38 @@
+/**
+ *
+ * Copyright 2015 Florian Schmaus
+ *
+ * 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 org.jivesoftware.smack.roster;
+
+/**
+ * Roster loaded listeners are invoked once the {@link Roster} was successfully loaded.
+ * <p>
+ * A common approach is to call
+ * {@link Roster#getEntriesAndAddListener(RosterListener, RosterEntries)} within
+ * {@link #onRosterLoaded(Roster)}, to initialize or update your UI components with the current
+ * roster state.
+ * </p>
+ */
+public interface RosterLoadedListener {
+
+    /**
+     * Called when the Roster was loaded successfully.
+     *
+     * @param roster the Roster that was loaded successfully.
+     */
+    public void onRosterLoaded(Roster roster);
+
+}