JavaFX 游戏循环中键盘输入事件的正确处理方法

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.input.KeyCode;
import javafx.scene.input.KeyEvent;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.event.EventHandler;
import javafx.animation.AnimationTimer;

import java.util.ArrayList;
import java.util.List;

// Main class (保持不变，但为了完整性在此处包含)
public class Main extends Application {
    private static Game game;

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

    @Override
    public void start(Stage stage) {
        game = new Game(stage);

        final long startNanoTime = System.nanoTime();
        new AnimationTimer() {
            public void handle(long currentNanoTime) {
                double t = (currentNanoTime - startNanoTime) / 1000000000.0;
                game.update(t);
                game.render();
            }
        }.start();
    }
}

// 修正后的 Game 类
class Game {
    private Stage stage;
    private Group root;
    private Scene scene;
    private Canvas canvas;
    private GraphicsContext gc;
    final static int WINDOW_WIDTH = 800;
    final static int WINDOW_HEIGHT = 600;

    // 使用实例变量来存储当前按下的键
    private List<KeyCode> input = new ArrayList<>();

    public Game(Stage stage) {
        this.stage = stage;
        this.root = new Group();
        this.scene = new Scene(this.root);
        this.canvas = new Canvas(WINDOW_WIDTH, WINDOW_HEIGHT);
        this.gc = this.canvas.getGraphicsContext2D();

        this.stage.setTitle("Pong");
        this.stage.setScene(this.scene);
        this.root.getChildren().add(this.canvas);

        // 在构造函数中只注册一次事件处理器
        this.scene.setOnKeyPressed(
            new EventHandler<KeyEvent>() {
                public void handle(KeyEvent e) {
                    KeyCode code = e.getCode();
                    if (!input.contains(code)) {
                        input.add(code);
                    }
                }
        });
        this.scene.setOnKeyReleased(
            new EventHandler<KeyEvent>() {
                public void handle(KeyEvent e) {
                    KeyCode code = e.getCode();
                    input.remove(code);
                }
        });
    }

    public void update(double time) {
        // handleInput现在只负责读取和处理input列表
        this.handleInput();

        // 游戏逻辑更新，例如根据input列表移动角色
        this.gc.setFill(Color.RED);
        this.gc.fillRect(0,0, WINDOW_WIDTH, WINDOW_HEIGHT);
    }

    public void render() {
        this.stage.show();
    }

    private void handleInput() {
        // 打印当前按下的键，用于调试
        System.out.println("当前按下的键: " + input);
        // 在实际游戏中，会根据input列表中的键来更新游戏状态
        // 例如：if (input.contains(KeyCode.LEFT)) { /* 角色向左移动 */ }
    }
}