Introduce empty selection functionality for NativeSelect. (#8336)

* Introduce empty selection functionality for NativeSelect.

Fixes vaadin/framework8-issues#545

1 files changed, 22 insertions, 4 deletions

diff --git a/client/src/main/java/com/vaadin/client/ui/nativeselect/NativeSelectConnector.java b/client/src/main/java/com/vaadin/client/ui/nativeselect/NativeSelectConnector.java
index 33c3170168..2426996ba4 100644
--- a/client/src/main/java/com/vaadin/client/ui/nativeselect/NativeSelectConnector.java
+++ b/client/src/main/java/com/vaadin/client/ui/nativeselect/NativeSelectConnector.java
@@ -17,6 +17,7 @@
 package com.vaadin.client.ui.nativeselect;
 
 import com.google.gwt.event.shared.HandlerRegistration;
+import com.google.gwt.user.client.ui.ListBox;
 import com.vaadin.client.annotations.OnStateChange;
 import com.vaadin.client.connectors.AbstractSingleSelectConnector;
 import com.vaadin.client.data.DataSource;
@@ -91,6 +92,21 @@ public class NativeSelectConnector
         getWidget().setTabIndex(getState().tabIndex);
     }
 
+    @OnStateChange({ "emptySelectionCaption", "emptySelectionAllowed" })
+    private void onEmptySelectionCaptionChange() {
+        ListBox listBox = getWidget().getListBox();
+        boolean hasEmptyItem = listBox.getItemCount() > 0
+                && listBox.getValue(0).isEmpty();
+        if (hasEmptyItem && getState().emptySelectionAllowed) {
+            listBox.setItemText(0, getState().emptySelectionCaption);
+        } else if (hasEmptyItem && !getState().emptySelectionAllowed) {
+            listBox.removeItem(0);
+        } else if (!hasEmptyItem && getState().emptySelectionAllowed) {
+            listBox.insertItem(getState().emptySelectionCaption, 0);
+            listBox.setValue(0, "");
+        }
+    }
+
     @Override
     public NativeSelectState getState() {
         return (NativeSelectState) super.getState();
@@ -112,9 +128,11 @@ public class NativeSelectConnector
         final VNativeSelect select = getWidget();
         final int itemCount = select.getListBox().getItemCount();
 
-        for (int i = range.getStart(); i < range.getEnd(); i++) {
+        int increment = getState().emptySelectionAllowed ? 1 : 0;
+        for (int i = range.getStart() + increment; i < range.getEnd()
+                + increment; i++) {
 
-            final JsonObject row = getDataSource().getRow(i);
+            final JsonObject row = getDataSource().getRow(i - increment);
 
             if (i < itemCount) {
                 // Reuse and update an existing item
@@ -127,8 +145,8 @@ public class NativeSelectConnector
             }
         }
 
-        for (int i = select.getListBox().getItemCount() - 1; i >= range
-                .getEnd(); i--) {
+        for (int i = select.getListBox().getItemCount() - 1; i >= range.getEnd()
+                + increment; i--) {
             // Remove extra items if the new dataset is smaller than the old
             select.getListBox().removeItem(i);
         }