java - KeyListener和MouseListener不起作用

我致力于制作一个简单的Java游戏，并且有一个很好的主意，即将我的输入处理与主游戏分开到一个单独的类中。我无法让InputHandler类实际接收输入。

主游戏类（DrawPanel.java）

package com.eriksaulnier.DesignedToFail;

import java.awt.*;
import java.awt.image.*;
import com.eriksaulnier.DesignedToFail.InputHandler;

import javax.swing.*;

public class DrawPanel extends JPanel {
private static final long serialVersionUID = 1L;
BufferedImage buffer;
InputHandler inputHandler;
Entity player;
Entity enemy;
public boolean spawnBullet = false;

public DrawPanel () {
    setIgnoreRepaint(true);
    setVisible(true);
    setFocusable(true);
    addKeyListener(inputHandler);
    addMouseListener(inputHandler);
    new InputHandler();
}

public void initialize() {
    buffer = new BufferedImage(800,600,BufferedImage.TYPE_INT_RGB);
    player = new Entity(370, 270);
    enemy = new Entity(100, 100);
}

public void update() {
    player.move();
}

public void checkCollisions() {
    if (player.getBounds().intersects(enemy.getBounds()))
        player.collision = true;
    else
        player.collision = false;
}

public void drawBuffer() {
    Graphics2D b = buffer.createGraphics();
    b.setColor(Color.white);
    b.fillRect(0, 0, 800, 600);
    if (player.collision == false) {
        b.setColor(Color.blue);
        b.fillRect(player.getX(), player.getY(), player.getWidth(), player.getHeight());
        b.setColor(Color.red);
        b.fillRect(enemy.getX(), enemy.getY(), enemy.getWidth(), enemy.getHeight());
        b.dispose();
    }
    else {
        b.setColor(Color.black);
        b.drawString("Collision!", 350, 300);
        b.dispose();
    }
}

public void drawScreen() {
    Graphics2D g = (Graphics2D)this.getGraphics();
    g.drawImage(buffer, 0, 0, this);
    Toolkit.getDefaultToolkit().sync();
    g.dispose();
}

public void startGame() {
    initialize();
    while(true) {
        try {
            update();
            checkCollisions();
            drawBuffer();
            drawScreen();
            Thread.sleep(15);
        }
        catch(Exception e) {
            e.printStackTrace();
        }
    }

}

}

InputHandler（InputHandler.java）

package com.eriksaulnier.DesignedToFail;

import java.awt.event.KeyListener;
import java.awt.event.MouseListener;
import java.awt.event.KeyEvent;
import java.awt.event.MouseEvent;

import javax.swing.JPanel;

public class InputHandler extends JPanel implements KeyListener, MouseListener {
public boolean isShooting = false;
Entity player;

public InputHandler () {
    System.out.println("Listener Works!");
}

public void mouseClicked(MouseEvent e) {

}

public void mousePressed(MouseEvent e) {
    int button = e.getButton();
    if (button == MouseEvent.BUTTON1)
        isShooting = true;
        System.out.println("Shooting!");
}

public void mouseReleased(MouseEvent e) {
    int button = e.getButton();
    if (button == MouseEvent.BUTTON1)
        isShooting = false;
        System.out.println("Not Shooting!");
}

public void mouseEntered(MouseEvent e) {

}

public void mouseExited(MouseEvent e) {

}

public void keyTyped(KeyEvent e) {

}

public void keyPressed(KeyEvent e) {
    int key = e.getKeyCode();
    if (key == KeyEvent.VK_W)
        player.up = true;
    if (key == KeyEvent.VK_S)
        player.down = true;
    if (key == KeyEvent.VK_A)
        player.left = true;
    if (key == KeyEvent.VK_D)
        player.right = true;
}

public void keyReleased(KeyEvent e) {
    int key = e.getKeyCode();
    if (key == KeyEvent.VK_W)
        player.up = false;
    if (key == KeyEvent.VK_S)
        player.down = false;
    if (key == KeyEvent.VK_A)
        player.left = false;
    if (key == KeyEvent.VK_D)
        player.right = false;
}

}

最佳答案

您似乎正在将null处理程序传递到GUI中。例如，您在哪里在实例化inputHandler变量之前使用它？

例如：

public class DrawPanel extends JPanel {
  //...

  InputHandler inputHandler; // here you declare the variable

  //...

  public DrawPanel () {
    setIgnoreRepaint(true); // why this line?
    setVisible(true); // not needed in a JPanel's code
    setFocusable(true);
    addKeyListener(inputHandler); // here you use a null variable
    addMouseListener(inputHandler); // ditto, here you use a null variable
    new InputHandler(); // I don't know what you're doing here
  }

在上面的代码中，在使用inputHandler = new InputHandler()之前，我看不到任何地方。您似乎在其中创建新InputHandler的行，没有将对象分配给任何变量或使用它，因此这似乎是徒劳的代码行，因此，我对如何确定该行的不确定之处发表了评论实现。请注意，这些问题与Swing无关，而与基本的Java核心无关。

也：


处理程序类不应扩展JPanels等Swing组件。他们应该仅实现侦听器接口。
您应该避免在Swing GUI中使用KeyListener，而尽可能使用Key Bindings。请Google搜索并查看“键绑定”教程，以获取更多有关此内容的信息。
在Oracle Swing教程中很好地解释了处理程序的使用。同样，请谷歌搜索并研究它们。我可以证明它们的用处，因为它们是我学习Swing编码的地方。

关于java - KeyListener和MouseListener不起作用，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/14149204/