除非具有菜单项，否则无法单击菜单

Question

我正在尝试使用javafx对菜单栏中菜单上的click事件添加操作。事实是，我看到了很多关于它的文章，但没有答案对我有用。我设法使用菜单上的“正在显示”来做到这一点，这很好，but仅当菜单中至少有一个菜单项时才触发此事件（和其他事件一样）。这不是我想要的东西，但我现在别无选择。

这里是fxml：

    <?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Menu?>
<?import javafx.scene.control.MenuBar?>
<?import javafx.scene.control.MenuItem?>
<?import javafx.scene.layout.BorderPane?>

<BorderPane maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" prefHeight="200.0" prefWidth="500.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="org.HangmanGameFXViews.view.MenuesActionsControlleur">
   <top>
      <MenuBar fx:id="menusBar" maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" onMouseReleased="#switchToAbout" prefWidth="400.0" BorderPane.alignment="CENTER">
         <menus>
            <Menu mnemonicParsing="false" text="Fichiers">
               <items>
                  <MenuItem mnemonicParsing="false" text="Nouveau" />
                  <MenuItem mnemonicParsing="false" onAction="#switchToScore" text="Scores" />
                  <MenuItem mnemonicParsing="false" onAction="#switchToRules" text="Règles" />
                  <MenuItem mnemonicParsing="false" onAction="#exit" text="Quitter" />
               </items>
            </Menu>
            <Menu fx:id="about" mnemonicParsing="false" onShowing="#switchToAbout" text="À propos">
               <items>
<!--                THIS THE DUMMY MENU I USE TO BE ABLE TO TRIGGER THE EVENT ON THE PARENT -->
                  <MenuItem fx:id="dummyMenuItem" mnemonicParsing="false" />
               </items></Menu>
         </menus>
      </MenuBar>
   </top>
</BorderPane>

视图控制器的代码：

package org.HangmanGameFXViews.view;
import org.HangmanGameFXViews.Main;
import javafx.event.ActionEvent;
import javafx.event.Event;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.scene.control.MenuItem;
import javafx.stage.Stage;

public class MenuesActionsControlleur {
    private Stage stageDialogue;
    private Main main;

    @FXML
    private Menu about;
    @FXML
    private MenuBar menusBar;
    @FXML
    private MenuItem dummyMenuItem;

    @FXML
    private void initialize() {

        about.addEventHandler(Event.ANY, new EventHandler<Event>() {

            @Override
            public void handle(Event event) {
                System.out.println("Showing Menu 1");
                System.out.println(event.getTarget().toString());
                System.out.println(event.getEventType().toString());

            }
        });
    }

    @FXML
    public void switchToRules() {
        main.switchToRules();
    }

    @FXML
    public void switchToAbout() {

        dummyMenuItem.setDisable(true);
        main.switchToAbout();
        dummyMenuItem.setDisable(false);

    }
    @FXML
    public void clickableMenu(ActionEvent e){
        System.out.println("Menu clicked");
    }

    @FXML
    public void switchToNew() {
        main.switchToNew();
    }
    @FXML
    public void switchToScore() {
        main.switchToScore();
    }

    public Stage getStageDialogue() {
        return stageDialogue;
    }

    public void setStageDialogue(Stage stageDialogue) {
        this.stageDialogue = stageDialogue;
    }

    @FXML
    public void exit() {
        stageDialogue.close();
    }

    public void setMainClass(Main m) {
        main = m;
        stageDialogue = main.getStagePrincipal();
    }
}

谢谢您的帮助。

Answer 1

就是说：安装自定义处理程序的基本思想是在代表Menu的styleableNode上进行安装。默认情况下，仅当Menu是ContextMenu中的一项时才实现对该节点的访问，而不是由MenuBar中的MenuButton表示时才实现（我认为这是一个错误，但这是另一个故事）。

所以我们必须自己做

扩展菜单

添加api设置包含菜单栏的对象
• 实现getStyleableNode以访问MenuButton
• 添加一些连线以重定向mouseReleased（或其他）触发菜单的动作

自定义菜单可能有点类似（显然不是生产质量：）：

public class MyMenu extends Menu {

    private MenuBar parentMenuBar;
    private Parent menuBarContainer;
    private MenuButton menuButton;

    private EventHandler<MouseEvent> redirector = this::redirect;

    public MyMenu(String string) {
        super(string);
    }

    public void setParentMenuBar(MenuBar menuBar) {
        this.parentMenuBar = menuBar;
        // tbd: cleanup if menuBar and/or its skin disposed/changed 
        if (menuBar != null) {
            menuBar.skinProperty().addListener((src, ov, nv) -> {
                if (nv instanceof MenuBarSkin && menuBar.getChildrenUnmodifiable().size() == 1) {
                    menuBarContainer = (Parent) menuBar.getChildrenUnmodifiable().get(0);
                    menuBarContainer.getChildrenUnmodifiable().addListener((ListChangeListener)c -> {
                        updateEventRedirector();
                    });
                    updateEventRedirector();
                }
            });
        }
    }

    protected void redirect(MouseEvent e) {
        // fire only if there are no items 
        if (getItems().size() == 0) fire();
    }

    /**
     * Rewire eventHandler when our styleable node is changed
     */
    private void updateEventRedirector() {
        if (menuButton != null) {
            menuButton.removeEventHandler(MouseEvent.MOUSE_RELEASED, redirector);
        }
        menuButton = getParentMenuButton();
        if (menuButton != null) {
            menuButton.addEventHandler(MouseEvent.MOUSE_RELEASED, redirector);
        }
    }

    @Override
    public Node getStyleableNode() {
        if (parentMenuBar != null && parentMenuBar.getChildrenUnmodifiable().size() == 1) {
            return menuButton;
        }
        return super.getStyleableNode();
    }

     private MenuButton getParentMenuButton() {
        if (parentMenuBar == null || parentMenuBar.getChildrenUnmodifiable().size() != 1) return null;
        // beware: implementation detail of menuBarSkin!
        Parent parent = (Parent) parentMenuBar.getChildrenUnmodifiable().get(0);
        for (Node child : parent.getChildrenUnmodifiable()) {
            // beware: internal api!
            if (child instanceof MenuBarButton) {
                MenuBarButton menuButton = (MenuBarButton) child;
                if (menuButton.menu == this) {
                    return menuButton;
                }
            }
        }
        return null;
    }
}

要使用：

bar = new MenuBar();
first = new MyMenu("dummy");
first.setParentMenuBar(bar);
first.setOnAction(e -> System.out.println("menu handler"));
bar.getMenus().addAll(first, new Menu("other"));