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  1. JDK
  2. JDK-8095404

ComboBox/ChoiceBox: items in popup not updated




      This issue is related to RT-15793
      That issue is "fixed" by hacking, the deeper
      issue (might be reported in RT-16072 which I'm not allowed to see)
      is that there are use-cases where change events must be fired
      based on identity of values (vs. based on equality which is
      default here).

      This issue report is yet another example where it blows. Pretty sure that you can dig up many more: it happens if

      - some collaborator is listening to a list (or map/set)-type property with a ChangeListener
      - installs a ListChangeListener to the property value (which updates some internal state) which must be re-wired by the ChangeListener

      As the ChangeListener isn't notified when the newList equals the oldList, the ListChangeListener keeps listening to the oldList.

      The hack applied to the related issue isn't manageable everywhere (in fact, it isn't even a fix for ListView et al controls, because it effective prevents install of custom skins/selectionModels) - you simply can't know who's listening ...

      Tentative short-term mitigations
      - strongly doc the current limitation, so that developers are aware of it
      - install InvalidationListener instead of ChangeListeners (short-circuit the lazy eval sounds like a payable price)

      Long-term fix might be an option in ExpressionHelper that checks for identity (as supported f.i. in JGoodies and use that option in controls' collection-valued properties.

      Run the example (is for ChoiceBox which can be replaced by ComboBox to see it as well) and see two variants of the same underlying bug as described in the doc.

       * Created on 22.09.2014
      package de.swingempire.fx.scene.control.selection;

      import javafx.application.Application;
      import javafx.collections.FXCollections;
      import javafx.collections.ObservableList;
      import javafx.scene.Scene;
      import javafx.scene.control.Button;
      import javafx.scene.control.ChoiceBox;
      import javafx.scene.layout.Pane;
      import javafx.scene.layout.VBox;
      import javafx.stage.Stage;

       * variant 1:
       * - choicebox with initially empty list
       * - click the "set empty items and add" button
       * - click drop-down arrow
       * - expected: popup contains added item
       * - actual: no popup shown (because it is still empty)
       * variant 2:
       * - click on "set not empty items"
       * - click drop-down arrow
       * - expected and actual: popup contains the items of the list
       * - click on "set not empty items and add"
       * - click drop-down arrow
       * - expected: popup contains the added item
       * - actual: popup only contains the two initial items of the list
      public class ItemsListenerBug extends Application {

           * @param args the command line arguments
          public static void main(String[] args) {

          public void start(Stage primaryStage) throws Exception {
             Pane ap = new VBox();
             // empty list
             ChoiceBox choice = new ChoiceBox();
             Button choiceAdd = new Button("set empty items and add choice");
             choiceAdd.setOnAction(ev -> {
                 ObservableList cl = FXCollections.observableArrayList();
                 // reset items to new empty list
                 // add item to new list
             // list with data
             String[] data = {"one", "two"};
             Button choiceSetOnly = new Button("set not empty items");
             choiceSetOnly.setOnAction(ev -> {
                 ObservableList cl = FXCollections.observableArrayList(data);
                 // set items to not-empty list
             Button choiceSetNotEmpty = new Button("set not empty items and add");
             choiceSetNotEmpty.setOnAction(ev -> {
                 ObservableList cl = FXCollections.observableArrayList(data);
                 // set items to new not-empty list with same items
                 // add new item to new list
             ap.getChildren().addAll(choice, choiceAdd, choiceSetOnly, choiceSetNotEmpty);
             Scene scene = new Scene(ap);




            jgiles Jonathan Giles
            fastegal Jeanette Winzenburg
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