java - 如何在单独的 java 类中包含关键监听器

Question

我已经研究单人乒乓球游戏有一段时间了，我已经成功地通过使用鼠标控制 Racket 来使代码正常工作。但是，我想弄清楚如何在该程序中包含一个关键监听器，以便我可以添加第二个桨以使其成为多人游戏。这是我现在拥有的代码:

主要类(还包含球类):

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.geom.*;
import java.util.concurrent.*;
import java.util.*;

public class Experiment extends JApplet {

    public static final int WIDTH = BallRoom.WIDTH;
    public static final int HEIGHT = BallRoom.HEIGHT;

    public PaintSurface canvas;

    public void init()
    {
        this.setSize(WIDTH, HEIGHT);
        canvas = new PaintSurface();
        this.add(canvas, BorderLayout.CENTER);

        ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(3);
        executor.scheduleAtFixedRate(new AnimationThread(this), 0L, 20L, TimeUnit.MILLISECONDS);

    }
}



class AnimationThread implements Runnable
{
    JApplet c;
    public AnimationThread(JApplet c)
    {
        this.c = c;
    }

    public void run()
    {
        c.repaint();
    }
}

class PaintSurface extends JComponent implements KeyListener
{
    int paddle_x = 0;
    int paddle_y = 360;

    int score = 0;
    float english = 1.0f;
    Ball ball;
    Color[] color = {Color.RED, Color.ORANGE, Color.MAGENTA, Color.ORANGE, Color.CYAN,   Color.BLUE};

    int colorIndex;

    @Override
    public void keyTyped(KeyEvent e)
    {
        System.out.println("Pressed" + e.getKeyChar()); //This doesn't show up when I type a key
    }

    @Override
    public void keyPressed(KeyEvent e)
    {

    }
    @Override
    public void keyReleased(KeyEvent e)
    {

    }

    public PaintSurface()
    {
        addMouseMotionListener(new MouseMotionAdapter()
        {
            public void mouseMoved(MouseEvent e)
            {
                if (e.getX() - 30 - paddle_x > 5)
                    english = 1.5f; 
                else if (e.getX() - 30 - paddle_x < 5)
                    english = -1.5f;
                else
                    english = 1.0f;
                paddle_x = e.getX() - 30;
            }
        });




        ball = new Ball(20);
    }


    public void paint(Graphics g)
    {
        Graphics2D g2 = (Graphics2D)g;
        Shape paddle = new Rectangle2D.Float(paddle_x, paddle_y, 60, 8);

        g2.setColor(color[colorIndex % 6]);

        if (ball.intersects(paddle_x, paddle_y, 60, 8) && ball.y_speed  > 0)
        {           
            ball.y_speed = -ball.y_speed * 1.1;
            ball.x_speed = ball.x_speed * 1.1;


            if (english != 1.0f)
            {
                colorIndex++;
            }
            score += Math.abs(ball.x_speed * 10);
        }

        if (ball.getY() + ball.getHeight() >= BallRoom.HEIGHT)
        {
            ball = new Ball(20);
            score -= 1000;
            colorIndex = 0;
        }
        ball.move();
        g2.fill(ball);

        g2.setColor(Color.BLACK);
        g2.fill(paddle);
        g2.drawString("Score: " + score, 250, 20);
    }
}

class Ball extends Ellipse2D.Float{
    public double x_speed, y_speed;
    private int d;
    private int width = BallRoom.WIDTH;
    private int height = BallRoom.HEIGHT;

    public Ball(int diameter)
    {
        super((int) (Math.random() * (BallRoom.WIDTH - 20) + 1), 0, diameter, diameter);
        this.d = diameter;
        this.x_speed = (int) (Math.random() * 5) + 1;
        this.y_speed = (int) (Math.random() * 5) + 1;
    }

    public void move()
    {       
        if (super.x < 0 || super.x > width - d)
            x_speed = -x_speed;
        if (super.y < 0 || super.y > height - d)
            y_speed = -y_speed;

        super.x += x_speed;
        super.y += y_speed;
    }
}

舞厅类:

import java.applet.*;
import java.awt.*;
import javax.swing.*;
import java.awt.geom.*;
import java.util.concurrent.*;

public class BallRoom extends JApplet{
public static final int WIDTH = 400;
public static final int HEIGHT = 400;
public void init()
{
    this.setSize(WIDTH, HEIGHT);
    this.setVisible(true);
}
}

Run class:


public class RunExperiment {
public static void main(String[] args)
{
    Experiment exp = new Experiment();

}
}

当我运行此代码时，打印语句不会执行，这使我相信它从未识别出该键被单击。我将不胜感激任何人能给我的任何帮助。

Answer 1

您需要在具有键监听器的组件上的某个位置调用 addKeyListener。

在您的情况下，您很可能想在 PaintSurface 构造函数中说 addKeyListener(this) 。