当另一个 FXML 已经处于活动状态时如何加载 FXML？

Question

我在我的 Java 项目中使用了 Oracle FXML 示例。 问题是我有 2 个 FXML 文件（load.fxml，main.fxml）。我首先加载load.fxml，然后想按下一个按钮触发一个方法（handleLoadButton()）来加载main.fxml。但这不起作用。我收到错误“JavaFX 应用程序线程”。所以也许我是个白痴，但我目前有点沮丧，因为我找不到任何解决方案。 我将如何加载 main.fxml？

到目前为止我的代码：

import java.io.IOException;

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

public class Main extends Application {

    private Stage myStage;

    public static void main(String[] args) {
        Application.launch(Main.class, args);
    }

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

        stage.setTitle("FXML Welcome");
        stage.setScene(new Scene(root, 300, 275));
        stage.show();

        myStage = stage;
    }

    @FXML
    private void handleLoadButton() throws IOException {
        Parent root = FXMLLoader.load(getClass().getResource("main.fxml"));

        myStage.setTitle("FXML Main");
        myStage.setScene(new Scene(root, 300, 275));
        myStage.show();
    }
}

我得到的错误：

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1449)
    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.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.Node.fireEvent(Node.java:6867)
    at javafx.scene.control.Button.fire(Button.java:179)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:193)
    at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:336)
    at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:329)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:64)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3311)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3151)
    at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3106)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1563)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2248)
    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:530)
    at com.sun.glass.ui.View.notifyMouse(View.java:924)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication$3$1.run(GtkApplication.java:89)
    at java.lang.Thread.run(Thread.java:724)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:75)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:279)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1446)
    ... 43 more
Caused by: java.lang.IllegalStateException: Application launch must not be called more than once
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:94)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:75)
    at javafx.application.Application.launch(Application.java:148)
    at program.Main.handleLoadButton(Main.java:35)
    ... 53 more

嘿，谢谢大家帮助我！

Answer 1

您的问题是，您使用 Application 类作为控制器。这意味着FXMLLoader 尝试创建Main 的另一个实例。您必须为控制器创建一个不同的类。

你修改后的 Main 类：

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

public class Main extends Application {

    private Stage myStage;

    public static void main(String[] args) {
        Application.launch(Main.class, args);
    }


    @Override
    public void start(Stage stage) throws Exception {
        FXMLLoader loader = new FXMLLoader();

        // this creates a instance of Controller now
        // and not a instance of Main
        Parent root = (Parent) loader.load(getClass().getResourceAsStream("load.fxml"));

        // get the controller corresponding to root
        Controller controller = loader.getController();

        // tell the controller that this is it's Main class
        controller.setMain(this);

        stage.setTitle("FXML Welcome");
        stage.setScene(new Scene(root, 300, 275));
        stage.show();

        myStage = stage;
    }

    public void handleLoadButton() throws IOException {
        Parent root = FXMLLoader.load(getClass().getResource("main.fxml"));

        myStage.setTitle("FXML Main");
        myStage.setScene(new Scene(root, 300, 275));
        myStage.show();
    }
}

控制器类：

import java.io.IOException;
import javafx.fxml.FXML;

public class Controller {

    @FXML
    private void handleLoadButton() throws IOException {
        myMain.handleLoadButton();
    }

    private Main myMain;

    public void setMain(Main myMain) {
        this.myMain = myMain;
    }

}

当然要替换load.fxml中的控制器类：

文件根节点中的fx:controller属性应该是：

fx:controller="Controller"

如果您不使用默认包，则可能需要添加包名称。