Fixed #294 and #301

Author: kevzlou7979

src/main/java/gwt/material/design/addins/client/combobox/MaterialComboBox.java

@@ -20,6 +20,7 @@
 package gwt.material.design.addins.client.combobox;
 
 import com.google.gwt.core.client.GWT;
+import com.google.gwt.core.client.Scheduler;
 import com.google.gwt.dom.client.Document;
 import com.google.gwt.dom.client.Style;
 import com.google.gwt.event.logical.shared.*;
@@ -302,6 +303,31 @@ public JQueryElement getDropdownParent() {
         return options.dropdownParent;
     }
 
+    /**
+     * Will get the Selection Results ul element containing all the combobox items.
+     */
+    public JQueryElement getDropdownResultElement() {
+        String dropdownId = getDropdownContainerElement().attr("id").toString();
+        if (dropdownId != null && !(dropdownId.isEmpty())) {
+            dropdownId = dropdownId.replace("container", "results");
+            return $("#" + dropdownId);
+        } else {
+            GWT.log("The element dropdown-result ul element is undefined.", new NullPointerException());
+        }
+        return null;
+    }
+
+    /**
+     * Will get the Selection dropdown container rendered
+     */
+    public JQueryElement getDropdownContainerElement() {
+        JQueryElement element = $(getElement()).find(".select2 .selection .select2-selection__rendered");
+        if (element == null) {
+            GWT.log("The element dropdown-container element is undefined.", new NullPointerException());
+        }
+        return element;
+    }
+
     /**
      * Set the upper label above the combobox
      */
@@ -650,6 +676,10 @@ public void setTags(boolean tags) {
         options.tags = tags;
     }
 
+    public void scrollTop(int offset) {
+        Scheduler.get().scheduleDeferred(() -> getDropdownResultElement().scrollTop(offset));
+    }
+
     @Override
     public void setEnabled(boolean enabled) {
         super.setEnabled(enabled);

src/test/java/gwt/material/design/addins/client/ui/MaterialComboBoxTest.java

@@ -28,6 +28,7 @@
 import gwt.material.design.addins.client.combobox.MaterialComboBox;
 import gwt.material.design.addins.client.combobox.events.SelectItemEvent;
 import gwt.material.design.addins.client.combobox.events.UnselectItemEvent;
+import gwt.material.design.addins.client.combobox.js.JsComboBox;
 import gwt.material.design.addins.client.ui.base.AbstractValueWidgetTest;
 import gwt.material.design.addins.client.ui.base.dto.User;
 import gwt.material.design.client.base.MaterialWidget;
@@ -239,4 +240,20 @@ public void testAddItemOption() {
         Label lblTitle = (Label) comboBox.getWidget(1);
         assertTrue(lblTitle.getElement().hasClassName(AddinsCssName.SELECT2LABEL));
     }
+
+    public void testElements() {
+        MaterialComboBox<User> comboBox = getWidget();
+
+        assertNotNull(comboBox.getDropdownContainerElement());
+        assertEquals(JsComboBox.$(comboBox.getElement()).find(".select2 .selection .select2-selection__rendered").html(), comboBox.getDropdownContainerElement().html());
+
+        final boolean[] firedOpenHandler = {false};
+        comboBox.addOpenHandler(openEvent -> {
+            firedOpenHandler[0] = true;
+            assertNotNull(comboBox.getDropdownResultElement());
+        });
+        comboBox.open();
+
+        assertTrue(firedOpenHandler[0]);
+    }
 }