为什么我的JAVAFX程序报错？

Question

为什么我的JAVAFX程序，明明代码语法都没有问题，却编译错误？
当我debug程序后，总是获得：“Exception in Application start method”的报错。
我用的是JAVASE-17和javafx-sdk-22.02。程序代码如下：

package application;

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.PerspectiveCamera;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.paint.PhongMaterial;
import javafx.scene.shape.Box;
import javafx.scene.transform.Rotate;
import javafx.scene.transform.Translate;
import javafx.stage.Stage;

public class Main extends Application {

    private double anchorX, anchorY;
    private double anchorAngleX = 0;
    private double anchorAngleY = 0;

    private final Rotate rotateX = new Rotate(0, Rotate.X_AXIS);
    private final Rotate rotateY = new Rotate(0, Rotate.Y_AXIS);
    private final Translate cameraTranslate = new Translate(0, 0, -500);

    @Override
    public void start(Stage primaryStage) {
        // Create a 3D box
        Box box = new Box(100, 100, 100);
        PhongMaterial material = new PhongMaterial(Color.BLUE);
        box.setMaterial(material);

        // Create a camera
        PerspectiveCamera camera = new PerspectiveCamera(true);
        camera.getTransforms().addAll(cameraTranslate, rotateX, rotateY);

        Group root = new Group();
        root.getChildren().addAll(box, camera);

        Scene scene3D = new Scene(root, 800, 600);
        scene3D.setFill(Color.BLACK);
        scene3D.setCamera(camera);

        // Handle mouse events for camera rotation
        scene3D.setOnMousePressed(event -> {
            anchorX = event.getSceneX();
            anchorY = event.getSceneY();
            anchorAngleX = rotateX.getAngle();
            anchorAngleY = rotateY.getAngle();
        });

        scene3D.setOnMouseDragged(event -> {
            rotateX.setAngle(anchorAngleX - (anchorY - event.getSceneY()));
            rotateY.setAngle(anchorAngleY + (anchorX - event.getSceneX()));
        });

        scene3D.setOnScroll(event -> {
            double delta = event.getDeltaY();
            cameraTranslate.setZ(cameraTranslate.getZ() + delta);
        });

        // Create a 2D target icon
        ImageView targetIcon = new ImageView(new Image("target.png")); // Replace with your image file
        targetIcon.setFitWidth(40);
        targetIcon.setFitHeight(40);

        // Alternatively, you could use a simple circle if you don't have an image:
        // Circle targetIcon = new Circle(20, Color.RED);
        // targetIcon.setStroke(Color.BLACK);

        // StackPane to hold both the 3D scene and the 2D icon
        StackPane stackPane = new StackPane();
        stackPane.getChildren().addAll(scene3D.getRoot(), targetIcon);

        // Ensure the target icon stays centered
        StackPane.setAlignment(targetIcon, javafx.geometry.Pos.CENTER);

        // Create the main scene and add the StackPane
        Scene scene = new Scene(stackPane, 800, 600);

        primaryStage.setTitle("Fixed Target Icon Example");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

Answer 1

该回答引用自GPT-deepseek, 由博主 GISer Liu 编写：

问题分析

用户在使用JavaFX开发程序时遇到了编译错误，报错信息为“Exception in Application start method”。尽管代码语法没有问题，但程序在启动时仍然报错。用户使用的环境是JavaSE-17和javafx-sdk-22.02。

解决方案

1. 检查模块依赖

JavaFX应用程序需要显式声明模块依赖。在Java 9及更高版本中，模块系统要求明确声明所需的模块。用户可能需要在其项目中添加对JavaFX模块的依赖。

2. 检查资源文件路径

用户在代码中使用了图像资源（target.png），需要确保该资源文件路径正确且文件存在。

3. 检查JavaFX库的正确配置

确保JavaFX库已正确配置在项目中，包括在IDE或构建工具（如Maven或Gradle）中正确引用JavaFX SDK。

详细步骤

1. 添加模块依赖

在模块描述文件（module-info.java）中添加对JavaFX模块的依赖。如果项目中没有module-info.java文件，需要创建一个：

module application {
    requires javafx.controls;
    requires javafx.graphics;
    requires javafx.base;
    requires javafx.media;
    requires javafx.swing;
    requires javafx.web;

    opens application to javafx.graphics;
}

2. 确保资源文件路径正确

确保target.png文件存在于类路径中，通常放在src/main/resources目录下。修改图像路径以确保正确加载：

ImageView targetIcon = new ImageView(new Image(getClass().getResourceAsStream("/target.png")));

3. 配置JavaFX库

在IDE中，确保JavaFX库已添加到项目库路径中。在Maven或Gradle项目中，确保已正确配置依赖项。

示例代码

以下是修改后的完整代码示例：

package application;

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.PerspectiveCamera;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.paint.PhongMaterial;
import javafx.scene.shape.Box;
import javafx.scene.transform.Rotate;
import javafx.scene.transform.Translate;
import javafx.stage.Stage;

public class Main extends Application {

    private double anchorX, anchorY;
    private double anchorAngleX = 0;
    private double anchorAngleY = 0;

    private final Rotate rotateX = new Rotate(0, Rotate.X_AXIS);
    private final Rotate rotateY = new Rotate(0, Rotate.Y_AXIS);
    private final Translate cameraTranslate = new Translate(0, 0, -500);

    @Override
    public void start(Stage primaryStage) {
        Box box = new Box(100, 100, 100);
        PhongMaterial material = new PhongMaterial(Color.BLUE);
        box.setMaterial(material);

        PerspectiveCamera camera = new PerspectiveCamera(true);
        camera.getTransforms().addAll(cameraTranslate, rotateX, rotateY);

        Group root = new Group();
        root.getChildren().addAll(box, camera);

        Scene scene3D = new Scene(root, 800, 600);
        scene3D.setFill(Color.BLACK);
        scene3D.setCamera(camera);

        scene3D.setOnMousePressed(event -> {
            anchorX = event.getSceneX();
            anchorY = event.getSceneY();
            anchorAngleX = rotateX.getAngle();
            anchorAngleY = rotateY.getAngle();
        });

        scene3D.setOnMouseDragged(event -> {
            rotateX.setAngle(anchorAngleX - (anchorY - event.getSceneY()));
            rotateY.setAngle(anchorAngleY + (anchorX - event.getSceneX()));
        });

        scene3D.setOnScroll(event -> {
            double delta = event.getDeltaY();
            cameraTranslate.setZ(cameraTranslate.getZ() + delta);
        });

        ImageView targetIcon = new ImageView(new Image(getClass().getResourceAsStream("/target.png")));
        targetIcon.setFitWidth(40);
        targetIcon.setFitHeight(40);

        StackPane stackPane = new StackPane();
        stackPane.getChildren().addAll(scene3D.getRoot(), targetIcon);

        StackPane.setAlignment(targetIcon, javafx.geometry.Pos.CENTER);

        Scene scene = new Scene(stackPane, 800, 600);

        primaryStage.setTitle("Fixed Target Icon Example");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

总结

通过添加模块依赖、确保资源文件路径正确以及正确配置JavaFX库，可以解决“Exception in Application start method”报错问题。用户应检查并修改上述提到的代码区域，以确保程序正确运行。

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