Fix moving a single component inside a split panel (#11920)

Change-Id: Ib9b3625e4104763143906eb1b7986ef7b3b80737

2 files changed, 41 insertions, 0 deletions

diff --git a/client/src/com/vaadin/client/ui/VAbstractSplitPanel.java b/client/src/com/vaadin/client/ui/VAbstractSplitPanel.java
index 269db23366..6ee88d51dd 100644
--- a/client/src/com/vaadin/client/ui/VAbstractSplitPanel.java
+++ b/client/src/com/vaadin/client/ui/VAbstractSplitPanel.java
@@ -511,6 +511,10 @@ public class VAbstractSplitPanel extends ComplexPanel {
         firstChild = w;
     }
 
+    public Widget getFirstWidget() {
+        return firstChild;
+    }
+
     /** For internal use only. May be removed or replaced in the future. */
     public void setSecondWidget(Widget w) {
         if (secondChild == w) {
@@ -525,6 +529,10 @@ public class VAbstractSplitPanel extends ComplexPanel {
         secondChild = w;
     }
 
+    public Widget getSecondWidget() {
+        return secondChild;
+    }
+
     @Override
     public void onBrowserEvent(Event event) {
         switch (DOM.eventGetType(event)) {
diff --git a/client/src/com/vaadin/client/ui/splitpanel/AbstractSplitPanelConnector.java b/client/src/com/vaadin/client/ui/splitpanel/AbstractSplitPanelConnector.java
index ce8b3c8fea..6bf03ad880 100644
--- a/client/src/com/vaadin/client/ui/splitpanel/AbstractSplitPanelConnector.java
+++ b/client/src/com/vaadin/client/ui/splitpanel/AbstractSplitPanelConnector.java
@@ -161,6 +161,35 @@ public abstract class AbstractSplitPanelConnector extends
         getLayoutManager().setNeedsLayout(this);
 
         getWidget().makeScrollable();
+
+        handleSingleComponentMove();
+    }
+
+    /**
+     * Handles the case when there is only one child component and that
+     * component is moved between first <-> second. This does not trigger a
+     * hierarchy change event as the list of children contains the same
+     * component in both cases.
+     */
+    private void handleSingleComponentMove() {
+        if (getChildComponents().size() == 1) {
+            Widget stateFirstChild = null;
+            Widget stateSecondChild = null;
+            if (getState().firstChild != null) {
+                stateFirstChild = ((ComponentConnector) getState().firstChild)
+                        .getWidget();
+            }
+            if (getState().secondChild != null) {
+                stateSecondChild = ((ComponentConnector) getState().secondChild)
+                        .getWidget();
+            }
+
+            if (stateFirstChild == getWidget().getSecondWidget()
+                    || stateSecondChild == getWidget().getFirstWidget()) {
+                handleHierarchyChange();
+            }
+        }
+
     }
 
     @Override
@@ -212,6 +241,10 @@ public abstract class AbstractSplitPanelConnector extends
 
     @Override
     public void onConnectorHierarchyChange(ConnectorHierarchyChangeEvent event) {
+        handleHierarchyChange();
+    }
+
+    private void handleHierarchyChange() {
         /*
          * When the connector gets detached, the state isn't updated but there's
          * still a hierarchy change -> verify that the child from the state is