paintComponent方法将不起作用 - Java

Question

当我使用此代码时，我的屏幕将为空。所以这意味着 我的paintComponent方法有些问题。但是，什么是错的？我该如何解决它？我的预期输出是一个深灰色的矩形和一个图像。

代码：

package _47b3n.seg.main.engine; 

import java.awt.Color; 
import java.awt.Graphics; 
import java.awt.event.KeyAdapter; 
import java.awt.event.KeyEvent; 
import javax.swing.ImageIcon; 
import javax.swing.JPanel; 
import _47b3n.seg.main.frame.Frame; 

public class Engine extends JPanel { 

public int xOff; 
public int yOff; 
public int x; 
public int y; 
public int fpsInt = 199; 

public boolean isRunning = true; 

public FPS fps = new FPS(); 

public static void main(String [] args) { 
    Frame frame = new Frame(); 
    frame.setFrame(800, 600, "Super easy game", "0.0.1"); 
    new Engine(); 
} 

public Engine() { 
    start(); 
} 

public void move() { 
    x+=xOff; 
    y+=yOff; 
} 

public void start() { 
    Thread loop = new Thread() { 
     public void run() { 
      gameLoop(); 
      addKeyListener(new keyInput()); 
     } 
    }; 
    loop.start(); 
} 


public void paintComponent(Graphics g) { 
    super.paintComponent(g); 
    g.setColor(Color.DARK_GRAY); 
    g.fillRect(10, 10, 10, 10); 
    g.drawImage(new ImageIcon("Poppetje.jpg").getImage(), x, y, null); 
} 

public void gameLoop() { 
    while(isRunning) { 
     move(); 
     repaint(); 
     fps.update(); 
     fpsInt++; 
     if (fpsInt == 200) { 
      System.out.println("[Console] " + fps.getFPS() + " FPS"); 
      fpsInt = 0; 
     } 
     try {Thread.sleep(17);} catch (InterruptedException e) {e.printStackTrace();} 
    } 
} 

public class keyInput extends KeyAdapter { 

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

     if(key == KeyEvent.VK_W) { 
      yOff = -1; 
     } 

     if (key == KeyEvent.VK_S) { 
      yOff = 1; 
     } 

     if (key == KeyEvent.VK_A) { 
      yOff = -1; 
     } 

     if (key == KeyEvent.VK_D) { 
      xOff = 1; 
     } 
    } 

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


     if (key == KeyEvent.VK_W) { 
      yOff = 0; 

     } 

     if (key == KeyEvent.VK_S) { 
      yOff = 0; 
     } 

     if (key == KeyEvent.VK_A) { 
      xOff = 0; 
     } 

     if (key == KeyEvent.VK_D) { 
      xOff = 0; 
     } 

    } 

} 

} 

感谢

Answer 1

不知道这是否是唯一的问题，但你永远面板添加到框架：

//new Engine(); 
Engine engine = new Engine(); 
frame.add(engine); 
frame.setVisible(true);