无法从 JavaFX 中的 MenuItem 获取场景

Question

I am trying to change the scene in a javafx stage based on menuItem click. Here is my sample.fxml:

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

<?import java.lang.*?>
<?import java.net.*?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.control.*?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.image.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.GridPane?>

<AnchorPane prefHeight="-1.0" prefWidth="560.0" styleClass="background" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/2.2" fx:controller="sample.Controller">
  <children>
    <MenuBar layoutY="0.0" maxWidth="1.7976931348623157E308" prefWidth="300.0" useSystemMenuBar="false" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="2.0">
      <menus>
        <Menu id="manageAccountsMenu" mnemonicParsing="false" onAction="#onManageAccountsMenuActionPerformed" text="Accounts" fx:id="manageAccountsMenu">
          <items>
            <MenuItem mnemonicParsing="false" onAction="#onTweetsMenuActionPerformed" text="Manage" fx:id="manageAccountsSubmenuItem" />
          </items>
        </Menu>
        <Menu mnemonicParsing="false" onAction="#onTweetsMenuActionPerformed" text="Tweets" fx:id="tweetsMenuItem" />
        <Menu mnemonicParsing="false" text="Retweets" />
      </menus>
    </MenuBar>
    <VBox id="VBox" alignment="CENTER" layoutY="24.0" spacing="5.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0">
      <children>
        <ScrollPane id="ScrollPane" fitToHeight="true" fitToWidth="true" prefViewportHeight="400.0" prefViewportWidth="300.0">
          <content>
            <TableView prefHeight="-1.0" prefWidth="-1.0" tableMenuButtonVisible="true">
              <columns>
                <TableColumn editable="false" prefWidth="75.0" text="SNO" />
                <TableColumn prefWidth="200.0" text="Account" />
                <TableColumn prefWidth="200.0" text="Status" />
                <TableColumn prefWidth="75.0" text="Actions" />
              </columns>
            </TableView>
          </content>
        </ScrollPane>
        <Button mnemonicParsing="false" text="Add Account" textAlignment="CENTER">
          <graphic>
            <ImageView fitHeight="150.0" fitWidth="200.0" mouseTransparent="true" pickOnBounds="true" preserveRatio="true">
              <image>
                <Image url="@addAccount.png" />
              </image>
            </ImageView>
          </graphic>
        </Button>
      </children>
    </VBox>
  </children>
  <stylesheets>
    <URL value="@darkTheme.css" />
  </stylesheets>
</AnchorPane>

Here is my Controller.java:

package sample;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.MenuItem;
import javafx.stage.Stage;

import java.net.URL;
import java.util.ResourceBundle;

public class Controller implements Initializable {
    @FXML
    protected void onManageAccountsMenuActionPerformed(ActionEvent event) {
        System.out.println("Manage Accbtnclick");
//        Node node=(Node) event.getSource();
//        Stage stage=(Stage) node.getScene().getWindow();
//
//        Scene scene = new Scene(root);
//        stage.setScene(scene);
//        stage.show();
    }
    @FXML
    protected void onTweetsMenuActionPerformed(ActionEvent event) {
        System.out.println("Manage Accbtnclick");
    Node node= (Node)event.getSource();
    Stage stage=(Stage) node.getScene().getWindow();
    Scene scene = Main.screens.get("tweet");
    stage.setScene(scene);
    stage.show();
    }

    @Override
    public void initialize(URL url, ResourceBundle resourceBundle) {
        //To change body of implemented methods use File | Settings | File Templates.
    }
}

Here is my Main.java:

package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.geometry.Pos;
import javafx.scene.Group;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.ProgressBar;
import javafx.scene.control.ProgressIndicator;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

import java.io.IOException;
import java.util.HashMap;

public class Main extends Application {

    public static HashMap<String,Scene> screens=new HashMap<String,Scene>();

    @Override
    public void start(Stage stage) {
        try {
            Parent accountScreen= FXMLLoader.load(getClass().getResource("sample.fxml"));
            Parent tweetScreen=FXMLLoader.load(getClass().getResource("tweetform.fxml"));
            //Parent retweetScreen=FXMLLoader.load(getClass().getResource("retweetform.fxml"));
            screens.put("account",new Scene(accountScreen));
            screens.put("tweet",new Scene(tweetScreen));
            //screens.put("retweet",new Scene(retweetScreen));
            stage.setTitle("Manage Accounts");
            stage.setScene(screens.get("account"));
            stage.show();
        } catch (IOException e) {
            e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
        }

    }
    public static void main(String[] args) {
        launch(args);
    }
}

When I click on the menuItem Manage under Accounts Menu, I get the following exception:

    "C:\Program Files\Java\jdk1.7.0_17\bin\java" -Didea.launcher.port=7541 "-Didea.launcher.bin.path=C:\Program Files (x86)\JetBrains\IntelliJ IDEA 12.1.4\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.7.0_17\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\jce.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\jfxrt.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\resources.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\rt.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.7.0_17\jre\lib\ext\zipfs.jar;C:\Users\rahulserver\IdeaProjects\DrawingText\out\production\DrawingText;C:\Program Files (x86)\JetBrains\IntelliJ IDEA 12.1.4\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain sample.Main
Manage Accbtnclick
Manage Accbtnclick
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1440)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.control.MenuItem.fire(MenuItem.java:456)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1188)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer$6.handle(ContextMenuContent.java:1139)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer$6.handle(ContextMenuContent.java:1137)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3328)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3168)
    at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3123)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1563)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2265)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:528)
    at com.sun.glass.ui.View.notifyMouse(View.java:922)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
    at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:73)
    at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:55)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:269)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1435)
    ... 40 more
Caused by: java.lang.ClassCastException: javafx.scene.control.MenuItem cannot be cast to javafx.scene.Node
    at sample.Controller.onTweetsMenuActionPerformed(Controller.java:29)
    ... 50 more

So how do I get the containing stage/scene from the menu Item clicked event handler?

EDIT The line

Node node= (Node)event.getSource();

in controller.java is line number 29 which is giving problems.

Answer 1

Your real error is shown in the second to last line of the stack trace:

Caused by: java.lang.ClassCastException: javafx.scene.control.MenuItem cannot be cast to javafx.scene.Node
    at sample.Controller.onTweetsMenuActionPerformed(Controller.java:29)

This error is referring to the following line from your controller:

Node node= (Node)event.getSource();

Looking at the JavaFX API Docs, neither MenuItem nor Menu are subclasses of Node. http://docs.oracle.com/javafx/2/api/javafx/scene/control/MenuItem.html http://docs.oracle.com/javafx/2/api/javafx/scene/control/Menu.html

I would suggest grabbing the source as an Object, then checking its type before continuing. Also, I ran into problems using the getSource() method; the getTarget() method worked better for me. Either way, you still need a way to get the to the Stage.

To do this, you might want to use the fx:id tag in your FXML instead of the id tag. This will allow you to inject the FXML elements directly into your controller. For example, you could grab the Stage from the MenuBar (which is a subclass of Node) by injecting the MenuBar element into your controller.

In the FXML:

<MenuBar fx:id="myMenuBar" layoutY="0.0" maxWidth="1.7976931348623157E308" prefWidth="300.0" useSystemMenuBar="false" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="2.0">

In the controller:

public class Controller implements Initializable {
    @FXML MenuBar myMenuBar;
    ...
    @FXML
    protected void onTweetsMenuActionPerformed(ActionEvent event) {
        System.out.println("Manage Accbtnclick");
        Stage stage = (Stage) myMenuBar.getScene().getWindow();
        Scene scene = Main.screens.get("tweet");
        stage.setScene(scene);
        stage.show();
    }
    ...
}

You may need to do a bit of tweaking here, but hopefully it helps.

Answer 2

Here is a way to get the Scene and Window based on a menu item being clicked without it being an injected FXML element, or without referencing it if you did create it with FXML. In other words by using the Event 's target.

In my problem I had a MenuButton with a dropdown menu (a ContextMenu as I found out, which I didn't know as I had created my menu in FXML) containing MenuItems and I wanted to open a FileChooser , which needs the Window as an argument, when the "Save" MenuItem was clicked.

Normally I would have gone down the route of getting the event's target, then the Parent, then the next Parent etc. and finally the Scene and then Window. As Menu and MenuItem are not Node s and therefore do not have Parent s In this case however I did the following:

FileChooser fileChooser = new FileChooser();

MenuItem menuItem = (MenuItem)event.getTarget();
ContextMenu cm = menuItem.getParentPopup();
Scene scene = cm.getScene();
Window window = scene.getWindow();

fileChooser.showSaveDialog(window);

Or, converting the bulk into a one line argument:

FileChooser fileChooser = new FileChooser();

fileChooser.showSaveDialog(((MenuItem)event.getTarget()).getParentPopup().getScene().getWindow());

Just adapt this as necessary based on your own scene-graph (ie how many parents you need to get through in cases of sub-menus etc) and what you are wanting to do once you have the Window , but once you get to the ContextMenu (the popup list of MenuItems ), you can get the Scene and then from that get the Window .

As an aside, here is the FXML I used to create my MenuButton , and hence why I didn't realise I had to get the ContextMenu through a call to getParentPopup() without some trial and error:

<MenuButton fx:id="menu" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" prefHeight="34.0" prefWidth="35.0" style="-fx-background-color: #6600ff; -fx-border-width: 0; -fx-mark-color: white; -fx-padding: 5;" textAlignment="CENTER" textFill="WHITE" underline="true">
    <items>
        <MenuItem fx:id="newSearch" mnemonicParsing="false" text="New Search" onAction="#clearSearch" />
        <SeparatorMenuItem  />
        <MenuItem fx:id="saveSearch" mnemonicParsing="false" text="Save Search" onAction="#saveSearch" />
        <MenuItem fx:id="loadSearch" mnemonicParsing="false" text="Load Search" />
        <SeparatorMenuItem  />
        <MenuItem fx:id="saveResults" mnemonicParsing="false" text="Save Results" />
        <MenuItem fx:id="loadResults" mnemonicParsing="false" text="Load Results" />
        <SeparatorMenuItem />
        <MenuItem fx:id="exportResults" mnemonicParsing="false" text="Export Results" />
    </items>
    <font>
        <Font name="Arial" size="12.0" />
    </font>
</MenuButton>

Answer 3

In JavaFX 15.0.1, you can use getOwnerWindow to get the Stage and get the Scene from the stage.

Stage owner = (Stage)menuItem.getParentPopup().getOwnerWindow();
Scene scene = owner.getScene();

Answer 4

Stage stage = (Stage) ((Node) myMenuBar).getScene().getWindow();