Perform menu item operations using identifiers as references (#2053)

Change-Id: Ib52c9c26f468c25b8c52fa3a99720898dc1b5c9a

appinventor/appengine/src/com/google/appinventor/client/widgets/DropDownButton.java

@@ -16,7 +16,9 @@ import com.google.gwt.user.client.ui.MenuItem;
 import com.google.gwt.user.client.ui.Image;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 /**
  * Class representing a drop-down button with its associated menu. Note
@@ -26,6 +28,7 @@ import java.util.List;
 public class DropDownButton extends TextButton {
 
   private final ContextMenu menu;
+  private final Map<String, MenuItem> itemsById = new HashMap<>();
   private final List<MenuItem> items;
   private final boolean rightAlign;
 
@@ -187,7 +190,22 @@ public class DropDownButton extends TextButton {
     if (item == null) {
       menu.addSeparator();
     } else {
-      items.add(menu.addItem(item.caption, true, item.command));
+      MenuItem menuItem = menu.addItem(item.caption, true, item.command);
+      itemsById.put(item.widgetName, menuItem);
+      items.add(menuItem);
+    }
+  }
+
+  /**
+   * Removes a menu item identified by {@code id} if it exists.
+   *
+   * @param id the identifier of the menu item
+   */
+  public void removeItemById(String id) {
+    if (itemsById.containsKey(id)) {
+      MenuItem item = itemsById.remove(id);
+      items.remove(item);
+      menu.removeItem(item);
     }
   }
 
@@ -201,6 +219,19 @@ public class DropDownButton extends TextButton {
     }
   }
 
+  /**
+   * Enables or disables a menu item identified by {@code id}.
+   *
+   * @param id the identifier of the menu item
+   * @param enabled true if the menu item should be enabled, false for disabled
+   */
+  public void setItemEnabledById(String id, boolean enabled) {
+    MenuItem item = itemsById.get(id);
+    if (item != null) {
+      item.setEnabled(enabled);
+    }
+  }
+
   public void setItemEnabled(String itemName, boolean enabled) {
     for (MenuItem item : items) {
       if (item.getText().equals(itemName)) {
@@ -216,6 +247,19 @@ public class DropDownButton extends TextButton {
     items.add(menu.addItem(item.caption, true, item.command));
   }
 
+  /**
+   * Sets the HTML content of a menu item, identified by {@code id}, to the given {@code html}.
+   *
+   * @param id the identifier of the menu item
+   * @param html the HTML content to use for the menu item
+   */
+  public void setItemHtmlById(String id, String html) {
+    MenuItem item = itemsById.get(id);
+    if (item != null) {
+      item.setHTML(html);
+    }
+  }
+
   public void setCaption(String caption) {
     this.setText(caption + " \u25BE ");
   }