[Bug #825] Fix bug

The previous listeners associated to the recommended allocation were
not removed, so pressing the recommended allocation button caused it
to be executed several times.

FEA: ItEr69S04BugFixing

navalplanner-webapp/src/main/java/org/navalplanner/web/common/Util.java

@@ -26,6 +26,7 @@ import static org.navalplanner.web.I18nHelper._;
 import java.math.BigDecimal;
 import java.util.ArrayList;
 import java.util.Date;
+import java.util.Iterator;
 import java.util.List;
 
 import org.zkoss.ganttz.util.ComponentsFinder;
@@ -578,4 +579,23 @@ public class Util {
         return ifNotFound.createAt(container);
     }
 
+    /**
+     * It removes all listeners registered for eventName and adds the new
+     * listener. It's ensured that the only listener left in the component for
+     * events of name eventName is uniqueListener
+     *
+     * @param component
+     * @param eventName
+     * @param uniqueListener
+     */
+    public static void ensureUniqueListener(Component component, String eventName,
+            EventListener uniqueListener) {
+        Iterator<?> listenerIterator = component.getListenerIterator(eventName);
+        while (listenerIterator.hasNext()) {
+            listenerIterator.next();
+            listenerIterator.remove();
+        }
+        component.addEventListener(eventName, uniqueListener);
+    }
+
 }

navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/TaskInformation.java

@@ -75,8 +75,9 @@ public class TaskInformation extends HtmlMacroComponent {
         gridTaskRows.setRowRenderer(newTaskRowsRenderer());
     }
 
-    public void onRecomendAllocation(EventListener event) {
-        btnRecommendedAllocation.addEventListener(Events.ON_CLICK, event);
+    public void onRecomendAllocation(EventListener eventListener) {
+        Util.ensureUniqueListener(btnRecommendedAllocation, Events.ON_CLICK,
+                eventListener);
     }
 
     public void showRecomendedAllocationButton() {