Introduce empty selection functionality for NativeSelect. (#8336)

* Introduce empty selection functionality for NativeSelect.

Fixes vaadin/framework8-issues#545

1 files changed, 56 insertions, 0 deletions

diff --git a/server/src/main/java/com/vaadin/ui/NativeSelect.java b/server/src/main/java/com/vaadin/ui/NativeSelect.java
index 9ae3409b66..f7427568ff 100644
--- a/server/src/main/java/com/vaadin/ui/NativeSelect.java
+++ b/server/src/main/java/com/vaadin/ui/NativeSelect.java
@@ -17,6 +17,7 @@
 package com.vaadin.ui;
 
 import java.util.Collection;
+import java.util.Objects;
 
 import com.vaadin.data.HasDataProvider;
 import com.vaadin.data.provider.DataProvider;
@@ -139,4 +140,59 @@ public class NativeSelect<T> extends AbstractSingleSelect<T>
     public ItemCaptionGenerator<T> getItemCaptionGenerator() {
         return super.getItemCaptionGenerator();
     }
+
+    /**
+     * Returns whether the user is allowed to select nothing in the combo box.
+     *
+     * @return true if empty selection is allowed, false otherwise
+     */
+    public boolean isEmptySelectionAllowed() {
+        return getState(false).emptySelectionAllowed;
+    }
+
+    /**
+     * Sets whether the user is allowed to select nothing in the combo box. When
+     * true, a special empty item is shown to the user.
+     *
+     * @param emptySelectionAllowed
+     *            true to allow not selecting anything, false to require
+     *            selection
+     */
+    public void setEmptySelectionAllowed(boolean emptySelectionAllowed) {
+        getState().emptySelectionAllowed = emptySelectionAllowed;
+    }
+
+    /**
+     * Returns the empty selection caption.
+     * <p>
+     * The empty string {@code ""} is the default empty selection caption.
+     *
+     * @see #setEmptySelectionAllowed(boolean)
+     * @see #isEmptySelectionAllowed()
+     * @see #setEmptySelectionCaption(String)
+     * @see #isSelected(Object)
+     *
+     * @return the empty selection caption, not {@code null}
+     */
+    public String getEmptySelectionCaption() {
+        return getState(false).emptySelectionCaption;
+    }
+
+    /**
+     * Sets the empty selection caption.
+     * <p>
+     * The empty string {@code ""} is the default empty selection caption.
+     * <p>
+     * If empty selection is allowed via the
+     * {@link #setEmptySelectionAllowed(boolean)} method (it is by default) then
+     * the empty item will be shown with the given caption.
+     *
+     * @param caption
+     *            the caption to set, not {@code null}
+     * @see #isSelected(Object)
+     */
+    public void setEmptySelectionCaption(String caption) {
+        Objects.nonNull(caption);
+        getState().emptySelectionCaption = caption;
+    }
 }