我是Java新手，我正在创建一个带时区的时钟 . 我对 JComboBox 的 repaint 方法有一点问题 . 如果我将 repaint() 放在我的代码中，我在Applet窗口中看不到 JComboBox ，如果我删除了 repaint() ，那么它是可见的 . 如您所知，将repaint（）放入代码中是非常必要的 .

我究竟做错了什么？

`包应用;

import java.awt . *;

import java.awt.event . *;

import java.util.Calendar;

import javax.swing . *;

公共类Alarm2扩展JFrame实现ItemListener，Runnable {

private Graphics dbg;

private Image dbImage;

JComboBox c=new JComboBox();

Thread t;

int h,m,s;

boolean alarm=false;

String time="";



TextField tf=new TextField("SEX:",10);

Alarm2(){





  setTitle("BALVEER");

  setSize(250,250);

  setResizable(false);

  setLocationRelativeTo(null);

  setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  c.addItem("MALE");

  c.addItem("FEMALE");

  setBackground(Color.GREEN);


  c.addItemListener(this);

  add(c);

  add(tf);

  setLayout(new FlowLayout(FlowLayout.RIGHT,10,195));

  setVisible(true);


}

public void aisha（）{

t=new Thread(this);

t.start();



}

public void run（）{

try{

       while(true){

       Calendar cal=Calendar.getInstance();

        h=cal.get(Calendar.HOUR);

        m=cal.get(Calendar.MINUTE);


        s=cal.get(Calendar.SECOND);

        t.sleep(1000);

        time=" "+h+" : "+m+" : "+s;

               repaint();



       }



   }

   catch(Exception e){



   }

}

public void itemStateChanged（ItemEvent e）{

tf.setText("SEX: "+e.getItem());

}



public void paint(Graphics g){

dbImage =createImage(getWidth(),getHeight()); 


dbg=dbImage.getGraphics();

draw(dbg);

g.drawImage(dbImage,0,0,this);

}

public void draw(Graphics g){

    g.setColor(Color.red);

    g.drawString("TIME:"+time, 50, 100);



}

public static void main(String[] args) {

      Alarm2 java=new Alarm2();

      java.aisha();

}

}`

java jcombobox