JAVA：程序未检测到使用KeyListener进行按键操作

Question

我正在Java中制作太空射击游戏。当我按下向上键时，它已经设置为向上移动，但它目前不工作。我在KeyListener界面中使用KeyPressed方法。这是我的代码。它在2个班。

Game.java

package main; 

import java.awt.Canvas; 
import java.awt.Color; 
import java.awt.Graphics; 
import java.awt.event.KeyEvent; 
import java.awt.event.KeyListener; 
import java.awt.image.BufferStrategy; 
import java.awt.image.BufferedImage; 
import java.io.IOException; 

import javax.imageio.ImageIO; 
import javax.swing.JFrame; 

public class Game extends Canvas implements Runnable, KeyListener { 

    private static final long serialVersionUID = 1L; 
    public static final int WIDTH = 800; 
    public static final int HEIGHT = 600; 
    public static final String TITLE = "Space Shooter"; 

    private boolean running = false; 
    private Thread thread; 

    private Player player; 

    private BufferedImage playerImage; 

    int playerx; 
    int playery; 

    public Game() { 
     player = new Player((WIDTH/2)-32, 400); 
     try { 
      playerImage = ImageIO.read(this.getClass().getResourceAsStream("/res/player.png")); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 

     addKeyListener(this); 
    } 

    private synchronized void start() { 
     if (running) 
      return; 

     running = true; 
     thread = new Thread(this); 
     thread.start(); 
    } 

    private synchronized void stop() { 
     if (!running) 
      return; 

     running = false; 
     try { 
      thread.join(); 
     } catch (InterruptedException e) { 
      e.printStackTrace(); 
     } 
     System.exit(1); 
    } 

    @Override 
    public void run() {  
     long lastTime = System.nanoTime(); 
     final double amountOfTicks = 60.0; 
     double ns = 1000000000/amountOfTicks; 
     double delta = 0; 
     int updates = 0; 
     int frames = 0; 
     long timer = System.currentTimeMillis(); 
     while (running) { 
      long now = System.nanoTime(); 
      delta += (now - lastTime)/ns; 
      lastTime = now; 
      if (delta > 1) { 
       tick(); 
       updates++; 
       delta--; 
      } 
      render(); 
      frames++; 

      if (System.currentTimeMillis() - timer > 1000) { 
       timer += 1000; 
       System.out.println(updates + " TICKS, " + frames + " FPS"); 
       updates = 0; 
       frames = 0; 
      } 
     } 
     stop(); 
    } 

    public void tick() { 
     playerx = player.getX(); 
     playery = player.getY(); 
    } 

    public void render() { 
     BufferStrategy bs = this.getBufferStrategy(); 
     if (bs == null) { 
      createBufferStrategy(3); 
      return; 
     } 
     Graphics g = bs.getDrawGraphics(); 

     g.drawImage(playerImage, playerx, playery, this); 

     g.dispose(); 
     bs.show(); 
    } 

    @Override 
    public void keyPressed(KeyEvent e) { 
     int key = e.getKeyCode(); 
     if (key == KeyEvent.VK_UP) { 
      player.setY(playery -= 5); 
     } 
    } 

    public void keyReleased(KeyEvent e) {} 
    public void keyTyped(KeyEvent e) {} 

    public static void main(String[] args) { 

     Game game = new Game(); 
     JFrame frame = new JFrame(TITLE); 

     frame.setSize(WIDTH, HEIGHT); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.setResizable(false); 
     frame.add(game); 
     frame.getContentPane().setBackground(Color.BLACK); 
     frame.setVisible(true); 

     game.start(); 

    } 

} 

Player.java

package main; 

public class Player { 

    int x, y; 

    public Player(int x, int y) { 
     this.x = x; 
     this.y = y; 
    } 

    public int getX() { 
     return x; 
    } 

    public int getY() { 
     return y; 
    } 

    public void setX(int x) { 
     this.x = x; 
    } 

    public void setY(int y) { 
     this.y = y; 
    } 

} 

Answer 1

当你点击游戏，然后按下键操作呢？ 如果是这样，所有你需要做的就是调用

setFocusable(true); 
requestFocus(); 

那么它应该工作