Iterate over copies of listener lists (#17477)

Allows adding/removing view change listeners from listeners.

Change-Id: Idb2227e1423c0297887f01f6df03b74e633ad917

1 files changed, 9 insertions, 2 deletions

diff --git a/server/src/com/vaadin/navigator/Navigator.java b/server/src/com/vaadin/navigator/Navigator.java
index ef5c61a294..65b3fec488 100644
--- a/server/src/com/vaadin/navigator/Navigator.java
+++ b/server/src/com/vaadin/navigator/Navigator.java
@@ -32,6 +32,7 @@ package com.vaadin.navigator;
  */
 
 import java.io.Serializable;
+import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
@@ -597,7 +598,10 @@ public class Navigator implements Serializable {
      *         block the navigation operation
      */
     protected boolean fireBeforeViewChange(ViewChangeEvent event) {
-        for (ViewChangeListener l : listeners) {
+        // a copy of the listener list is needed to avoid
+        // ConcurrentModificationException as a listener can add/remove
+        // listeners
+        for (ViewChangeListener l : new ArrayList<ViewChangeListener>(listeners)) {
             if (!l.beforeViewChange(event)) {
                 return false;
             }
@@ -647,7 +651,10 @@ public class Navigator implements Serializable {
      *            view change event (not null)
      */
     protected void fireAfterViewChange(ViewChangeEvent event) {
-        for (ViewChangeListener l : listeners) {
+        // a copy of the listener list is needed to avoid
+        // ConcurrentModificationException as a listener can add/remove
+        // listeners
+        for (ViewChangeListener l : new ArrayList<ViewChangeListener>(listeners)) {
             l.afterViewChange(event);
         }
     }