为什么我的Java repaint（）方法不起作用？

Question

Heyo，为了完成我的大学作业，我需要绘制一些图像并进行竞赛，但是即使在绘制图像（在本例中为图标）时，我也被困住了。我现在想在许多JPanel之一上画任何东西（这就是为什么我有drawLine方法，只是为了对其进行测试），但是我的repaint（）方法没有调用我的paintComponent方法，为什么？

import java.awt.*;  
import javax.swing.*;  
import java.lang.Math; 


public class Races{
   private int numberOfRacers;

   public Races(int numberOfRacers){
      this.numberOfRacers = numberOfRacers;
      JFrame frame = new JFrame("Races - Name Surname");

      Icon icon = new ImageIcon("races.jpg");
      frame.setLayout(new GridLayout(numberOfRacers, 1));
      frame.setSize(icon.getIconWidth()*20, (icon.getIconWidth()*2)*numberOfRacers);
      frame.setVisible(true);
      frame.setLocationRelativeTo(null);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      try{
         Thread.sleep(1000);  // Sleeping 1 sec 
         System.out.println("Sleeping one second for the user!");
      }catch(InterruptedException ie){
         System.out.println(ie);
      }


      for(int i = 0; i < numberOfRacers; i++){
         innerRacer racer = new innerRacer();
         frame.add(racer.panel);
         //JLabel iconLabel = new JLabel(icon);
         //iconLabel.setHorizontalAlignment(JLabel.LEFT);
         //panel.add(iconLabel);
         Thread t = new Thread(racer);
         t.start();

      }
   }

   public static void main(String args[]){

      if(args.length > 0 && Integer.parseInt(args[0]) > 0 && Integer.parseInt(args[0]) < 100){
         Races races = new Races(Integer.parseInt(args[0]));   // From command line number of racers
         System.out.println("Number of racers: " + args[0]);
      }else{
         Races races = new Races(5);      // Default number of racers
         System.out.println("Number of racers: 5");
      }
   }

   public class innerRacer extends JPanel implements Runnable{ 
      JPanel panel;
      Icon icon;
      public innerRacer(){
         panel = new JPanel();
         panel.setBackground(Color.WHITE);

         icon = new ImageIcon("races.jpg");
      } //end of innerRacer constructor

      @Override
         public void run(){
            repaint();     
            System.out.println("TEST");  
         }
     @Override
     public void paintComponent(Graphics g){
         super.paintComponent(g);
         g.drawLine(10, 20, 30, 40);
         System.out.println("Why is this one not called?");
         icon.paintIcon(panel, g, 0, 0);
     } 

   } // end of innerRacer class
} //end of Races class

提前感谢。

Answer 1

您添加了JPanel所包含的innerRacer而不是JPanel所包含的innerRacer。

更改：

     frame.add(racer.panel);

至：

     frame.add(racer);