Question

现在我正在玩JavaFX，我想做的是在已经使用Scene Builder创建的画布上绘制某种动画。不幸的是，我无法在画布上得到任何东西，因为我在使用GraphicsContext做任何事情时都会遇到一些异常。

我对Java和JavaFX都很陌生，我一直在寻找很多东西来解决这个问题，但我无法解决这个问题。

循环似乎已成功运行，因为我能够获取控件打印件，但与gameCanvas Canvas上的渲染图形相关的任何内容都会触发异常。

错误：（例如，由于gc.setFill(Color.RED)方法中的run()，我得到了这些错误。

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
    at Game.lambda$0(Game.java:54)
    at javafx.graphics/com.sun.scenario.animation.shared.TimelineClipCore.visitKeyFrame(Unknown Source)
    at javafx.graphics/com.sun.scenario.animation.shared.TimelineClipCore.playTo(Unknown Source)
    at javafx.graphics/javafx.animation.Timeline.doPlayTo(Unknown Source)
    at javafx.graphics/javafx.animation.AnimationAccessorImpl.playTo(Unknown Source)
    at javafx.graphics/com.sun.scenario.animation.shared.InfiniteClipEnvelope.timePulse(Unknown Source)
    at javafx.graphics/javafx.animation.Animation.doTimePulse(Unknown Source)
    at javafx.graphics/javafx.animation.Animation$1.lambda$timePulse$0(Unknown Source)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.graphics/javafx.animation.Animation$1.timePulse(Unknown Source)
    at javafx.graphics/com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(Unknown Source)
    at javafx.graphics/com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(Unknown Source)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(Unknown Source)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(Unknown Source)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulseFromQueue(Unknown Source)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$11(Unknown Source)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(Unknown Source)
    at java.base/java.lang.Thread.run(Unknown Source)

我的代码：

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

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.paint.Color;
import javafx.util.Duration;
import javafx.scene.shape.*;

public class Game implements Initializable, Runnable, ControlledScreen {

    @FXML
    public Canvas gameCanvas;
    private GraphicsContext gc;
    public enum difficulties {EASY, MEDIUM, HARD};

    difficulties difficultyLevel;
    int score = 0;
    Snake snake;
    Food food;
    boolean running = true;
    private Timeline gameloop = new Timeline();

    @Override
    public void setScreenParent(ScreensController screenPage) {

    }

    public void setLevelEasy() {
        difficultyLevel = difficulties.EASY;
    }

    public void setLevelMedium() {
        difficultyLevel = difficulties.MEDIUM;
    }

    public void setLevelHard() {
        difficultyLevel = difficulties.HARD;
    }

    @Override

    public void run() { 

        KeyFrame frame = new KeyFrame(Duration.seconds(0.2), event -> {
            if (!running)
                return;
            System.out.println("The loop's running, yai!");

            gc.setFill(Color.RED);

        });

        gameloop.getKeyFrames().add(frame);
        gameloop.setCycleCount(Timeline.INDEFINITE);
        gameloop.play();

    }

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        gc = gameCanvas.getGraphicsContext2D();
    }

}

提前致谢！

使用Scene Builder创建的画布上绘图

0 个答案: