如何从主类使用/调用 KeyEvents 以在子类中使用

Question

好吧，基本上我已经在主类中设置了这些关键事件：https://prnt.sc/jhbxz9。

我在这里尝试完成的是使用在我的主类中设置的这些关键事件，这样我就可以在我的子类（播放器）的 peformAction 下编写一个带有 if/else 语句的方法，以使播放器在按下键时移动并且释放时停止移动。目前我所能做的就是始终向一个方向移动直到它离开屏幕而不需要按下任何键，但我希望它在按下 VK_LEFT 时改变 velX 但我不知道如何参考到我的子类中的关键事件而不会破坏代码。最后一件事是我注意到每个关键事件下都有 setKey，这让我觉得我需要使用 setKeys，但仍然没有。

如果您不能被要求阅读所有代码，请使用完整的屏幕截图。 玩家类（子类）：http://prntscr.com/jhbx58 + http://prntscr.com/jhbxim

GameManager 类（主类）：http://prntscr.com/jhbxz9

GameManager 类：

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Toolkit;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.swing.JFrame;

public class GameManager extends JFrame implements KeyListener {

    private int canvasWidth;
    private int canvasHeight;
    private int borderLeft;
    private int borderTop;
    private BufferedImage canvas;
    private Stage stage;
    private Enemy[] enemies;
    private Player player;
    private Goal goal;
    private Graphics gameGraphics;
    private Graphics canvasGraphics;
    private int numEnemies;
    private boolean continueGame;

    public static void main(String[] args) {
// During development, you can adjust the values provided in the brackets below
// as needed. However, your code must work with different/valid combinations
// of values.
        GameManager managerObj = new GameManager(1920, 1280, 30);
    }

    public GameManager(int preferredWidth, int preferredHeight, int maxEnemies) {
        this.borderLeft = getInsets().left;
        this.borderTop = getInsets().top;
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        if (screenSize.width < preferredWidth) {
            this.canvasWidth = screenSize.width - getInsets().left - getInsets().right;
        } else {
            this.canvasWidth = preferredWidth - getInsets().left - getInsets().right;
        }
        if (screenSize.height < preferredHeight) {
            this.canvasHeight = screenSize.height - getInsets().top - getInsets().bottom;
        } else {
            this.canvasHeight = preferredHeight - getInsets().top - getInsets().bottom;
        }
        setSize(this.canvasWidth, this.canvasHeight);
        setResizable(false);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);
        addKeyListener(this);
        Random rng = new Random(2);
        this.canvas = new BufferedImage(this.canvasWidth, this.canvasHeight, BufferedImage.TYPE_INT_RGB);
// Create a Stage object to hold the background images
        this.stage = new Stage();
// Create a Goal object with its initial x and y coordinates
        this.goal = new Goal(this.canvasWidth / 2, Math.abs(rng.nextInt()) % this.canvasHeight);
// Create a Player object with its initial x and y coordinates
        this.player = new Player(this.canvasWidth - (Math.abs(rng.nextInt()) % (this.canvasWidth / 2)),
                (Math.abs(rng.nextInt()) % this.canvasHeight));
// Create the Enemy objects, each with a reference to this (GameManager) object
// and their initial x and y coordinates.
        this.numEnemies = maxEnemies;
        this.enemies = new Enemy[this.numEnemies];
        for (int i = 0; i < this.numEnemies; i++) {
            this.enemies[i] = new Enemy(this, Math.abs(rng.nextInt()) % (this.canvasWidth / 4),
                    Math.abs(rng.nextInt()) % this.canvasHeight);
        }
        this.gameGraphics = getGraphics();
        this.canvasGraphics = this.canvas.getGraphics();
        this.continueGame = true;
        while (this.continueGame) {
            updateCanvas();
        }
        this.stage.setGameOverBackground();
        updateCanvas();
    }

    public void updateCanvas() {
        long start = System.nanoTime();
// If the player is alive, this should move the player in the direction of the
// key that has been pressed
// Note: See keyPressed and keyReleased methods in the GameManager class.
        this.player.performAction();
// If the enemy is alive, the enemy must move towards the goal. The goal object
// is obtained
// via the GameManager object that is given at the time of creating an Enemy
// object.
// Note: The amount that the enemy moves by must be much smaller than that of
// the player above
// or else the game becomes too hard to play.
        for (int i = 0; i < this.numEnemies; i++) {
            this.enemies[i].performAction();
        }
        if ((Math.abs(this.goal.getX() - this.player.getX()) < (this.goal.getCurrentImage().getWidth() / 2))
                && (Math.abs(this.goal.getY() - this.player.getY()) < (this.goal.getCurrentImage().getWidth()
                / 2))) {
            for (int i = 0; i < this.numEnemies; i++) {
// Sets the image of the enemy to the "dead" image and sets its status to
// indicate dead
                this.enemies[i].die();
            }
// Sets the image of the enemy to the "dead" image and sets its status to
// indicate dead
            this.goal.die();
// Sets the background of the stage to the finished game background.
            this.stage.setGameOverBackground();
            this.continueGame = false;
        }
// If an enemy is close to the goal, the player and goal die
        int j = 0;
        while (j < this.numEnemies) {
            if ((Math.abs(this.goal.getX() - this.enemies[j].getX()) < (this.goal.getCurrentImage().getWidth() / 2))
                    && (Math.abs(this.goal.getY() - this.enemies[j].getY())
                    < (this.goal.getCurrentImage().getWidth() / 2))) {
                this.player.die();
                this.goal.die();
                this.stage.setGameOverBackground();
                j = this.numEnemies;
                this.continueGame = false;
            }
            j++;
        }
        try {
// Draw stage
            this.canvasGraphics.drawImage(stage.getCurrentImage(), 0, 0, null);
// Draw player
            this.canvasGraphics.drawImage(player.getCurrentImage(),
                    this.player.getX() - (this.player.getCurrentImage().getWidth() / 2),
                    this.player.getY() - (this.player.getCurrentImage().getHeight() / 2), null);
// Draw enemies
            for (int i = 0; i < this.numEnemies; i++) {
                this.canvasGraphics.drawImage(this.enemies[i].getCurrentImage(),
                        this.enemies[i].getX() - (this.enemies[i].getCurrentImage().getWidth() / 2),
                        this.enemies[i].getY() - (this.enemies[i].getCurrentImage().getHeight()
                        / 2), null);
            }
// Draw goal
            this.canvasGraphics.drawImage(this.goal.getCurrentImage(),
                    this.goal.getX() - (this.goal.getCurrentImage().getWidth() / 2),
                    this.goal.getY() - (this.goal.getCurrentImage().getHeight() / 2), null);
        } catch (Exception e) {
            System.err.println(e.getMessage());
        }
// Draw everything.
        this.gameGraphics.drawImage(this.canvas, this.borderLeft, this.borderTop, this);
        long end = System.nanoTime();
        this.gameGraphics.drawString("FPS: " + String.format("%2d", (int) (1000000000.0 / (end - start))),
                this.borderLeft + 50, this.borderTop + 50);
    }

    public Goal getGoal() {
        return this.goal;
    }

    public void keyPressed(KeyEvent ke) {
// Below, the setKey method is used to tell the Player object which key is
// currently pressed.
// The Player object must keep track of the pressed key and use it for
// determining the direction
// to move.
        if (ke.getKeyCode() == KeyEvent.VK_LEFT) {
            this.player.setKey('L', true);
        }
        if (ke.getKeyCode() == KeyEvent.VK_RIGHT) {
            this.player.setKey('R', true);
        }
        if (ke.getKeyCode() == KeyEvent.VK_UP) {
            this.player.setKey('U', true);
        }
        if (ke.getKeyCode() == KeyEvent.VK_DOWN) {
            this.player.setKey('D', true);
        }
        if (ke.getKeyCode() == KeyEvent.VK_ESCAPE) {
            this.continueGame = false;
        }
    }

    @Override
    public void keyReleased(KeyEvent ke) {
// Below, the setKey method is used to tell the Player object which key is
// currently released.
// The Player object must keep track of the pressed key and use it for
// determining the direction
// to move.
        if (ke.getKeyCode() == KeyEvent.VK_LEFT) {
            this.player.setKey('L', false);
        }
        if (ke.getKeyCode() == KeyEvent.VK_RIGHT) {
            this.player.setKey('R', false);
        }
        if (ke.getKeyCode() == KeyEvent.VK_UP) {
            this.player.setKey('U', false);
        }
        if (ke.getKeyCode() == KeyEvent.VK_DOWN) {
            this.player.setKey('D', false);
        }
    }

    @Override
    public void keyTyped(KeyEvent ke) {
    }
}

我的玩家类（子类）：

import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;

public class Player {

private BufferedImage imageRunning;
private BufferedImage imageOver;
private BufferedImage imageCurrent;
int valx = 500;
int valy = 100;


public Player(int valx, int valy) {

    try {
        this.imageRunning = ImageIO.read(new File("C:/Users/HUS/Desktop/Assigment222/images/player-alive.png"));
        this.imageOver = ImageIO.read(new File("C:/Users/HUS/Desktop/Assigment222/images/player-dead.png"));
    } catch (IOException e) {
        e.printStackTrace();
    }
    this.imageCurrent = this.imageRunning;
}

public BufferedImage getCurrentImage() {
    return this.imageCurrent;
}

public void setGameOverBackground() {
    this.imageCurrent = this.imageOver;
}

public void performAction() {
    if(Player.setKey('D', true) == true) {
        this.valx += 2;
    }
    else if(Player.setKey('D', false) == false) {
        this.valx = 0;
    }
    return;
}

public int getX() {
    return valx;
}

public int getY() {
    return valy;
}

public void die() {
    return;

}

public static boolean setKey(char c, boolean b) {
    return b;


}

}

Answer 1

所以当keyPressed 或keyReleased 被调用时，它们会依次调用Player.setKey。当它被调用时，你存储状态。

例如...

public class Player {

    //...

    // I really, really, really don't static been used this way, it
    // has a bad code smell about it...
    public static Set<Character> inputState = new TreeSet<Character>();

    //...

    public static void setKey(char c, boolean b) {
        if (b) {
            inputState.add(c);
        } else {
            inputState.remove(c);
        }
    }

}

所以，这实际上就是将char 添加到Set 或删除它。因为Set保证了唯一性，所以我们不需要关心这个键是否已经被按下了。

然后当调用performAction 时，您检查输入是否在Set 中并采取适当的措施...

public void performAction() {
    if (inputState.contains('U')) {
        // Going up
    } else if (inputState.contains('D')) {
        // Going down
    }
    //... other inputs
}