java - 为什么我在 Java 中收到 javafx.fxml.LoadException

Question

这个问题已经有答案了:

What is a NullPointerException, and how do I fix it? (12 个回答)

已关闭 4 年前。

我正在为我的学校项目制作数独，需要打开新窗口，其中将列出高分，但每次我单击菜单项时，控制台都会抛出错误，我不知道我能做什么。

我已经尝试在互联网上查找某些内容，但我尝试的所有内容都导致了相同的错误

package controller;

import java.io.IOException;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.control.Button;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.stage.Modality;
import javafx.stage.Stage;
import model.GameBoard;

public class Controller implements Initializable {

    @FXML
    Button button_one;
    @FXML
    Button button_two;
    @FXML
    Button button_three;
    @FXML
    Button button_four;
    @FXML
    Button button_five;
    @FXML
    Button button_six;
    @FXML
    Button button_seven;
    @FXML
    Button button_eight;
    @FXML
    Button button_nine;
    @FXML
    Canvas canvas;

    GameBoard gameboard;

    int psr; // ausgewählte reihe
    int psc; // ausgewählte spalte



    @Override
    public void initialize(URL location, ResourceBundle resources) {
        gameboard = new GameBoard();
        psr = 0;
        psc = 0;
        GraphicsContext context = canvas.getGraphicsContext2D();
        try {
            drawOnCanvas(context);
        } catch (IOException e) {

            e.printStackTrace();
        }

    }

    public void drawOnCanvas(GraphicsContext context) throws IOException {
        context.clearRect(0, 0, 450, 450);
        for (int row = 0; row < 9; row++) {
            for (int col = 0; col < 9; col++) {
                int posy = row * 50 + 2;
                int posx = col * 50 + 2;
                int width = 46;
                context.setFill(Color.LIGHTGRAY);
                context.fillRoundRect(posx, posy, width, width,10,10);
            }
        }
        context.setStroke(Color.RED);
        context.setLineWidth(2);
        context.strokeRoundRect(psc * 50 + 2, psr * 50 + 2, 46, 46, 10, 10);

        int[][] initial = gameboard.getInitial();
        for (int row = 0; row < 9; row++) {
            for (int col = 0; col < 9; col++) {
                int posy = row * 50 + 30;
                int posx = col * 50 + 20;
                context.setFill(Color.BLACK);
                context.setFont(new Font(20));
                if (initial[row][col] != 0) {
                    context.fillText(initial[row][col] + "", posx, posy);
                }

            }
        }

        int[][] player = gameboard.getPlayer();
        for(int row = 0; row < 9;row++) {
            for(int col = 0; col < 9; col++) {
                int posy = row * 50 + 30;
                int posx = col * 50 + 20;
                context.setFill(Color.RED);
                context.setFont(new Font(20));
                if(player[row][col] != 0) {
                    context.fillText(player[row][col] + "", posx, posy);
                }
            }
        }


        //Die vier Linien für die 3x3 Trennung
        context.setStroke(Color.BLACK);
        context.strokeLine(450, 150, 0, 150);
        context.strokeLine(450, 300, 0, 300);
        context.strokeLine(150, 0, 150, 450);
        context.strokeLine(300, 0, 300, 450);
        context.setLineWidth(3);


        if(gameboard.checkSuccess()) {
            context.clearRect(0, 0, 450, 450);
            context.setFill(Color.GREEN);
            context.setFont(new Font(36));
            context.fillText("SUPER!", 150, 200);
            newWindow();






        }



    }

    public void canvasMouseClick() throws IOException{
        canvas.setOnMouseClicked(new EventHandler<MouseEvent>() {

            @Override
            public void handle(MouseEvent event) {
                int mousex = (int) event.getX();
                int mousey = (int) event.getY();

                psr = (int) (mousey / 50);
                psc = (int) (mousex / 50);

                // System.out.println(psr + "," + psc);

                try {
                    drawOnCanvas(canvas.getGraphicsContext2D());
                } catch (IOException e) {

                    e.printStackTrace();
                }

            }
        });

    }







public void button1pressed() throws IOException{
                gameboard.modifyPlayer(1, psr, psc);
                drawOnCanvas(canvas.getGraphicsContext2D());

            }




public void button2pressed() throws IOException{
            gameboard.modifyPlayer(2, psr, psc);
            drawOnCanvas(canvas.getGraphicsContext2D());

        }







public void button3pressed() throws IOException{
            gameboard.modifyPlayer(3, psr, psc);
            drawOnCanvas(canvas.getGraphicsContext2D());

           }





 public void button4pressed() throws IOException{
            gameboard.modifyPlayer(4, psr, psc);
            drawOnCanvas(canvas.getGraphicsContext2D());

         }




public void button5pressed() throws IOException{
            gameboard.modifyPlayer(5, psr, psc);
            drawOnCanvas(canvas.getGraphicsContext2D());

         }





public void button6pressed() throws IOException{
            gameboard.modifyPlayer(6, psr, psc);
            drawOnCanvas(canvas.getGraphicsContext2D());
        }





public void button7pressed() throws IOException{
            gameboard.modifyPlayer(7, psr, psc);
            drawOnCanvas(canvas.getGraphicsContext2D());
        }





public void button8pressed() throws IOException {
            gameboard.modifyPlayer(8, psr, psc);
            drawOnCanvas(canvas.getGraphicsContext2D());
        }





public void button9pressed() throws IOException {
            gameboard.modifyPlayer(9, psr, psc);
            drawOnCanvas(canvas.getGraphicsContext2D());
        }





    public void neuesSpiel() throws IOException {
        gameboard = new GameBoard();
        psr = 0;
        psc = 0;
        GraphicsContext context = canvas.getGraphicsContext2D();
        drawOnCanvas(context);
    }

    public void newWindow() throws IOException {

        try {
            FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("/controller/highscore.fxml"));
            VBox root1 = (VBox) fxmlLoader.load();
            Stage stage = new Stage();
            stage.setScene(new Scene(root1));  
            stage.show();
        } catch(Exception e) {
            e.printStackTrace();
        }


    }



}

堆栈跟踪:

Mai 21, 2019 5:31:30 PM javafx.fxml.FXMLLoader$ValueElement processValue
WARNING: Loading FXML document with JavaFX API of version 11.0.1 by JavaFX runtime of version 8.0.181
Mai 21, 2019 5:31:32 PM javafx.fxml.FXMLLoader$ValueElement processValue
WARNING: Loading FXML document with JavaFX API of version 11.0.1 by JavaFX runtime of version 8.0.181

javafx.fxml.LoadException: 
/C:/Users/Luka%20Lajic/eclipse-workspace/Sudoku/bin/controller/highscore.fxml

at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2579)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
at controller.Controller.newWindow(Controller.java:223)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.Trampoline.invoke(Unknown Source)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1771)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
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.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
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.control.MenuItem.fire(MenuItem.java:462)
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1405)
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.lambda$createChildren$343(ContextMenuContent.java:1358)
at com.sun.javafx.event.CompositeEventHandler$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.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$MouseHandler.process(Scene.java:3757)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$353(GlassViewEventHandler.java:432)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
    at controller.Controller.initialize(Controller.java:58)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
    ... 56 more

Answer 1

Caused by: java.lang.NullPointerException
at controller.Controller.initialize(Controller.java:58)

表明错误出现在您的 Controller 类的第 58 行。这似乎是这一行:

GraphicsContext context = canvas.getGraphicsContext2D();

如果是这样，如果 canvas 为空，就会发生这种情况。

您很可能能够通过确保正确实例化 canvas 来解决该错误，但如果您需要进一步帮助，可以阅读更多内容 here .