JavaFX：如何在同一fxml文件中动态更改控制器？

Question

专家！ 我只想对几个控制器使用一个按钮，以便使代码简短。 在玻色窗格的底部，我制作了用于更改边框窗格中心视图的按钮，一旦单击了下一个按钮，它便更改了位于边框窗格中心的另一个视图。 但是，如果我单击复选按钮，我希望显示displayMassageLabel的消息会出现，但是会出错。是否有人可以解决此问题。 以下是我在下面简单编写的示例代码。

ChangeControllerTestMain.java

package javafxapplication2;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

/**
 *
 * @author James
 */
public class ChangeControllerTestMain extends Application {

    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("Main.fxml"));

        Scene scene = new Scene(root);

        stage.setScene(scene);
        stage.show();
    }

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

}

Main.fxml

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

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<BorderPane fx:id="borderPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="javafxapplication2.MainController">
   <bottom>
      <HBox alignment="CENTER" prefHeight="39.0" prefWidth="600.0" spacing="100.0" BorderPane.alignment="CENTER">
         <children>
            <Button fx:id="backButton" mnemonicParsing="false" onAction="#handleBackButtonAction" text="&lt;Back" />
            <Button fx:id="checkButton" mnemonicParsing="false" onAction="#handleCheckButtonAction" text="Check" />
            <Button fx:id="nextButton" mnemonicParsing="false" onAction="#handleNextButtonAction" text="Next&gt;" />
         </children></HBox>
   </bottom>
</BorderPane>

MainColtroller.java

package javafxapplication2;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;

/**
 *
 * @author James
 */
public class MainController implements Initializable {

    @FXML
    private BorderPane borderPane;
    private AnchorPane anchorPane;
    private Label displayMassageLabel;

    @FXML
    private Button backButton;
    @FXML
    private Button checkButton;
    @FXML
    private Button nextButton;

    private int currentMenuNum;
    private String currentViewerPath;
    private String pathList[] = {"StartDisplay.fxml", "Menu1Display.fxml", "Menu2Display.fxml", "Menu3Display.fxml"};

    private Menu1DisplayController menu1DisplayController = new Menu1DisplayController();
    private Menu2DisplayController menu2DisplayController = new Menu2DisplayController();
    private Menu3DisplayController menu3DisplayController = new Menu3DisplayController();

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
        currentMenuNum = 0;
        currentViewerPath = pathList[currentMenuNum];
        System.out.println(currentViewerPath);
        setControlItems(currentViewerPath, currentMenuNum);
    }

    private void setControlItems(String path, int currentMenuNum) {
        //Display setting for menu
        FXMLLoader fxmlLoader = new FXMLLoader();
        try {
            fxmlLoader.setLocation(getClass().getResource(path));
            anchorPane = fxmlLoader.load();
            //connectionViewerController = (ConnectionViewerController) fxmlLoader.getController();
        } catch (Exception e) {
            System.out.println(e.getStackTrace().toString());
            System.out.println(e.getMessage());
        }
        borderPane.setCenter(anchorPane);

        if (currentMenuNum == 1) {
            menu1DisplayController = (Menu1DisplayController) fxmlLoader.getController();
        } else if (currentMenuNum == 2) {
            menu2DisplayController = (Menu2DisplayController) fxmlLoader.getController();
        } else if (currentMenuNum == 3) {
            menu3DisplayController = (Menu3DisplayController) fxmlLoader.getController();
        }
    }

    private String getCurrentViewerPath(int currentMenuNum) {
        currentViewerPath = pathList[currentMenuNum];
        return currentViewerPath;
    }

    @FXML
    private void handleBackButtonAction(ActionEvent event) {
        if (currentMenuNum == 0) {
            return;
        }
        currentMenuNum = currentMenuNum - 1;
        currentViewerPath = getCurrentViewerPath(currentMenuNum);
        setControlItems(currentViewerPath, currentMenuNum);
    }

    @FXML
    private void handleNextButtonAction(ActionEvent event) {
        currentMenuNum = currentMenuNum + 1;
        currentViewerPath = getCurrentViewerPath(currentMenuNum);
        setControlItems(currentViewerPath, currentMenuNum);
    }

    @FXML
    private void handleCheckButtonAction(ActionEvent event) {
        displayMassageLabel.setText("Welcome Menu " + currentMenuNum);
    }
}

StartDisplay.fxml

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

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane id="AnchorPane" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1">
   <children>
      <VBox alignment="CENTER" layoutX="10.0" layoutY="10.0" prefHeight="361.0" prefWidth="600.0" spacing="20.0">
         <children>
            <Label text="Display Message" />
            <Label text="Start Display" />
            <Label fx:id="displayMassageLabel" />
         </children>
      </VBox>
   </children>
</AnchorPane>

Menu1DisplayController.java

package javafxapplication2;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;

/**
 * FXML Controller class
 *
 * @author James
 */
public class Menu1DisplayController implements Initializable {
    @FXML
    private Label displayMassageLabel;

    /**
     * Initializes the controller class.
     */
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }   

    @FXML
    private void handleCheckButtonAction(ActionEvent event) {
        displayMassageLabel.setText("Welcome Menu 1");
    }

}

Menu1Display.fxml

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

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane id="AnchorPane" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="javafxapplication2.Menu1DisplayController">
   <children>
      <VBox alignment="CENTER" layoutX="10.0" layoutY="10.0" prefHeight="361.0" prefWidth="600.0" spacing="20.0">
         <children>
            <Label text="Display Message" />
            <Label text="Current Menu is 1" />
            <Label fx:id="displayMassageLabel" />
         </children>
      </VBox>
   </children>
</AnchorPane>

菜单2和3的FXML文件和控制器与菜单1相同。 请帮我。

这些是错误。

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1770)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1653)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8390)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3758)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3486)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2495)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:350)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$350(GlassViewEventHandler.java:385)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$$Lambda$105/472212858.get(Unknown Source)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:404)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:384)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:927)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
    at com.sun.glass.ui.win.WinApplication$$Lambda$36/1963387170.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1765)
    ... 50 more
Caused by: java.lang.NullPointerException
    at javafxapplication2.MainController.handleCheckButtonAction(MainController.java:101)
    ... 60 more

Answer 1

添加功能

public void setDisplayMessageLabel(String message){
     displayMassageLabel.setText(message);
}

到所有的Menu1DisplayControllers（Menu1，Menu2，...）。 知道您可以像这样从MainContorller调用此函数

@FXML
private void handleCheckButtonAction(ActionEvent event) {
   if (currentMenuNum == 1) {
        menu1DisplayController.setDisplayMassageLabel("Welcome Menu " + currentMenuNum;
    } else if (currentMenuNum == 2) {
        menu2DisplayController.setDisplayMassageLabel("Welcome Menu " + currentMenuNum;
    } else if (currentMenuNum == 3) {
        menu3DisplayController.setDisplayMassageLabel("Welcome Menu " + currentMenuNum;
    }

}