Improved fix for #11614 (#11618)

* #11614: Added test which demonstrates that the fix is incomplete

* #11614: UI.doRefresh() only calls navigator when the navigation state actually changes

* Added javadoc to Navigator.getCurrentNavigationState()

* Minor: Removed accidental star imports

2 files changed, 18 insertions, 12 deletions

diff --git a/server/src/main/java/com/vaadin/navigator/Navigator.java b/server/src/main/java/com/vaadin/navigator/Navigator.java
index 7107f7451d..fc22b19c3b 100644
--- a/server/src/main/java/com/vaadin/navigator/Navigator.java
+++ b/server/src/main/java/com/vaadin/navigator/Navigator.java
@@ -1272,4 +1272,17 @@ public class Navigator implements Serializable {
         ui.setNavigator(null);
     }
 
+    /**
+     * Returns the current navigation state for which the
+     * {@link #getCurrentView()} has been constructed. This may differ to
+     * {@link #getState()} in case the URL has been changed on the browser and
+     * the navigator wasn't yet given an opportunity to construct new view. The
+     * state is in the form of
+     * <code>current-view-name/optional/parameters</code>
+     *
+     * @return the current navigation state, may be {@code null}.
+     */
+    public String getCurrentNavigationState() {
+        return currentNavigationState;
+    }
 }
diff --git a/server/src/main/java/com/vaadin/ui/UI.java b/server/src/main/java/com/vaadin/ui/UI.java
index 2a3b913e16..e48390666e 100644
--- a/server/src/main/java/com/vaadin/ui/UI.java
+++ b/server/src/main/java/com/vaadin/ui/UI.java
@@ -31,6 +31,7 @@ import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Objects;
 import java.util.concurrent.Future;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -162,12 +163,6 @@ public abstract class UI extends AbstractSingleComponentContainer
             this);
 
     /**
-     * Holder for old navigation state, needed in doRefresh in order not to call
-     * navigateTo too often
-     */
-    private String oldNavigationState;
-
-    /**
      * Scroll Y position.
      */
     private int scrollTop = 0;
@@ -880,12 +875,10 @@ public abstract class UI extends AbstractSingleComponentContainer
         // PushStateNavigation. Call navigateTo only if state have
         // truly changed
         Navigator navigator = getNavigator();
-        if (navigator != null) {
-            if (oldNavigationState == null) oldNavigationState = getNavigator().getState();
-            if (!navigator.getState().equals(oldNavigationState)) {
-                navigator.navigateTo(navigator.getState());
-                oldNavigationState = navigator.getState();
-            }
+        if (navigator != null
+                && !Objects.equals(navigator.getCurrentNavigationState(),
+                        navigator.getState())) {
+            navigator.navigateTo(navigator.getState());
         }
     }