如何在java中正确使用keylistener

Question

我正在尝试使用KeyListner 使用左右键来前后移动游戏中的角色，但我似乎无法稍微移动角色。我看着这个答案没有运气：

How to use keyListener properly in Java 和 How do i use KeyListener in java?

这是我的代码：

package test2;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Test
{
    public static void main(String[] args)
    {
        Frame A1 = new Frame();
    }

}

class Frame
{
    JFrame window;

    public Frame ()
    {
        awt();
    }

    public void awt()
    {
        Design A2 = new Design()
        {
            @Override
            public void keyTyped(KeyEvent e)
            {
                throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
            }

            @Override
            public void keyPressed(KeyEvent e)
            {
                throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
            }

            @Override
            public void keyReleased(KeyEvent e)
            {
                throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
            }
        };

        window = new JFrame("Kyo's test");

        window.setVisible(true);
        window.setSize(1280, 786);
        window.add(A2);

        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}


abstract class Design extends JPanel implements ActionListener, KeyListener
{
    // Timer objects for character and saws
    Timer movementOfCharacter = new Timer(5, this);
    Timer movementOfSaw = new Timer(15, this);

    // Variables for movement
    int xAxisOfCharacter = 50, velocityOfCharacter=2, yAxisOfSaw = 0, velocityOfSaw = 10;

    private Image tree, background, character, saw;


    // Constructor
    Design()
    {
        movementOfCharacter.start();

        addKeyListener(this);

        setFocusable(true);
        setFocusTraversalKeysEnabled(false);
    }

    // Constructor of Graphics
    protected void paintComponent(Graphics graphics)
    {
        super.paintComponent(graphics);

        Graphics2D graphics2d = (Graphics2D) graphics;

        graphics2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);

        movementOfSaw.start();

        // Body for background
        {
            ImageIcon whale = new ImageIcon(this.getClass().getResource("whale.jpg"));
            background = whale.getImage();

            graphics2d.drawImage(background, 0, 0, getWidth(), getHeight(), this);
        }

        // Body for trees
        {
            ImageIcon environment = new ImageIcon(this.getClass().getResource("Tree_Alt.png"));
            tree = environment.getImage();

            graphics2d.drawImage(tree, getWidth()/8, getHeight()-217, this);
            graphics2d.drawImage(tree, (getWidth()/5)*2, getHeight()-217, this);
            graphics2d.drawImage(tree, (getWidth()/6)*4, getHeight()-217, this);
        }

        // Body for Saws of death
        {
            ImageIcon sawOfDeath = new ImageIcon(this.getClass().getResource("saw.gif"));
            saw = sawOfDeath.getImage();

            // First saw
            {
                graphics2d.drawImage(saw, (getWidth()/11), yAxisOfSaw, 100, 100, this);
            }

            // Second saw
            {
                graphics2d.drawImage(saw, (getWidth()/7)*2, yAxisOfSaw, 100, 100, this);
            }

            // Thirf saw
            {
                graphics2d.drawImage(saw, (getWidth()/2)-10, yAxisOfSaw, 100, 100, this);
            }

            // Fourth saw
            {
                graphics2d.drawImage(saw, (getWidth()/6)*4, yAxisOfSaw, 100, 100, this);
            }

            // Fifth saw
            {
                graphics2d.drawImage(saw, (getWidth()/6)*5, yAxisOfSaw, 100, 100, this);
            }
        }

        // Body for exit
        {
            graphics.setColor(Color.red);
            graphics.fillRect(getWidth()-5, getHeight()-150, 5, 150);
        }

        // Body for Character
        {
            ImageIcon blanka = new ImageIcon(this.getClass().getResource("Blank.gif"));
            character = blanka.getImage();

            graphics2d.drawImage(character, xAxisOfCharacter, getHeight()-150, 150, 155, this);
        }
    }

    public void actionPerformed(ActionEvent e)
    {
        yAxisOfSaw += velocityOfSaw;

        if(yAxisOfSaw > 0 || yAxisOfSaw < getHeight()-100)
            velocityOfSaw = -velocityOfSaw;

        repaint();
    }

    public void keyPressed(KeyEvent e)
    {
        int key = e.getKeyCode();

        if(key == KeyEvent.VK_LEFT)
        {
            velocityOfCharacter = -5;
        }
        if(key == KeyEvent.VK_RIGHT)
        {
            velocityOfCharacter = 5;
        }
    }

    public void keyTyped(KeyEvent e)
    {
    }

    public void keyReleased(KeyEvent e)
    {
    }
}

谁能告诉我我在哪里做错了什么？

Answer 1

问题

当你这样做时

Design A2 = new Design() {
    @Override
    public void keyTyped(KeyEvent e) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
     public void keyPressed(KeyEvent e) {
         throw new UnsupportedOperationException("Not supported yet."); 
    }

    @Override
    public void keyReleased(KeyEvent e) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
};

您正在覆盖您在 Design 抽象类中编写的代码，只是抛出异常。

解决方案

您的Design 类不必是abstract，因为它没有未实现的方法。所以我可以看到 2 种方法来使用你在 Design 类中编写的代码：

第一种方式

删除 abstract 关键字，以便您可以像使用 new 关键字的普通类一样实例化您的 Design 类。所以以这种方式声明Design 类：

class Design extends JPanel implements ActionListener, KeyListener

然后以这种方式实例化 A2：

Design A2 = new Design();

第二种方式

如果出于某种原因，您需要抽象类，请以这种方式实例化您的 A2 对象：

Design A2 = new Design() {};

这将起作用并且不会覆盖您在Design 类中编写的任何方法。但这没什么意义，上面的第一种方式更有意义。

注意事项

注 1

现在，如果您在 Design.keyPressed 中添加打印输出，您可以看到它被调用（您将在控制台中看到日志）：

public void keyPressed(KeyEvent e) {
    System.out.println("KeyEvent: "+e);
    int key = e.getKeyCode();
    ...

注2

另外看keyPressed方法，我觉得你还需要更新字符X轴坐标，所以在你的if语句后面加上这行：

xAxisOfCharacter += velocityOfCharacter;

应该是这样的：

public void keyPressed(KeyEvent e) {
    System.out.println("KeyEvent: "+e);
    int key = e.getKeyCode();

    if(key == KeyEvent.VK_LEFT) {
        velocityOfCharacter = -5;
    }
    else if(key == KeyEvent.VK_RIGHT) {
        velocityOfCharacter = 5;
    }
    xAxisOfCharacter += velocityOfCharacter;
}