大侠们，帮个忙！我编个计时器出现问题！

Question

好像没有地方，重画窗口，每次label变了要强制调用repaint()，否则label不会变。你每次改变窗口大小时，label就会变的！

Answer 1

每一次
L.setText("XXXXXXXX");
后
L.repaint();

Answer 2

////////////////////////////////////////做了如下修改
void btn_Clock_actionPerformed(ActionEvent e) {
        ClockThread nowClock=new ClockThread();
        nowClock.setLabel(jLabel1);
        nowClock.start();
/*        jLabel1.setText(nowClock.repaint());
        Date now=new Date();
        String s;
        s=now.getHours()+":"+now.getMinutes() +":"+now.getSeconds();
        jLabel1.setText(s);*/
    }
}class ClockThread extends Thread {
    private Thread clockTh=null;
    JLabel L;
    public  void  setLabel(JLabel L)
    {
      this.L = L;
    }
    /*
    public void start(){        if(clockTh==null){
            //clockTh=new Thread(this,"ClockThread");
            clockTh.start();
        }    }
    */
    public void run(){
        //Thread myThread=Thread.currentThread();
        //start();
        //System.out.println("currentThread = "+myThread);
        System.out.println("this = "+this);
        //System.out.println("clockTh = "+clockTh);
        try{
            Thread.sleep(1000);
        }catch(InterruptedException e){}
        L.setText("Zhangping");
    /*        try{
                Thread.sleep(1000);
            }catch(InterruptedException e){}
            L.setText("23:59:59");*/        //while(clockTh==myThread){
          while  (true)
          {
            L.setText(repaint());
            try{
                Thread.sleep(1000);
            }catch(InterruptedException e){}
          }
           // //i//f(clockTh.getThreadGroup()!=myThread.getThreadGroup())
              //  System.out.println("Flase");
            //e//lse
               // System.out.println("True");
            //}
        }
    public String repaint(){
        String s;
        Date now=new Date();
        s=now.getHours() +":"+now.getMinutes()+":"+now.getSeconds();
        return s;
    }
}

Answer 3

也许不太规范，但你所要的功能是实现了：
import javax.swing.*;
import java.awt.*;
import javax.swing.border.*;
import java.awt.event.*;
import java.util.*;
import java.util.*;
import javax.swing.*;
import java.lang.Thread;
/**
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2002</p>
 * <p>Company: </p>
 * @author unascribed
 * @version 1.0
 */public class Clock {    ClockThread nowClock=new ClockThread();    private static JPanel jPanel1 = new JPanel();
    private JLabel jLabel1 = new JLabel();
    private JButton btn_Start = new JButton();
    private JButton btn_Clean = new JButton();
    private JButton btn_Clock = new JButton();
    private BorderLayout borderLayout1 = new BorderLayout();
    private TitledBorder titledBorder1;    public Clock() {
        try {
            jbInit();
        }
        catch(Exception e) {
            e.printStackTrace();
        }
    }
    private void jbInit() throws Exception {
        titledBorder1 = new TitledBorder("");
        jLabel1.setBackground(Color.white);
        jLabel1.setFont(new java.awt.Font("Dialog", 1, 14));
        jLabel1.setForeground(Color.red);
        jLabel1.setBorder(titledBorder1);
        jLabel1.setHorizontalAlignment(SwingConstants.CENTER);
        jLabel1.setText("jLabel1");
        btn_Start.setBackground(Color.orange);
        btn_Start.setFont(new java.awt.Font("Dialog", 0, 14));
        btn_Start.setForeground(Color.red);
        btn_Start.setBorder(titledBorder1);
        btn_Start.setToolTipText("");
        btn_Start.setMnemonic('S');
        btn_Start.setText("开始(S)");
        btn_Start.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(ActionEvent e) {
                btn_Start_actionPerformed(e);
            }
        });
        btn_Clean.setBackground(Color.orange);
        btn_Clean.setFont(new java.awt.Font("Dialog", 0, 14));
        btn_Clean.setForeground(Color.red);
        btn_Clean.setBorder(titledBorder1);
        btn_Clean.setMnemonic('C');
        btn_Clean.setText(" 清零(C)");
        btn_Clean.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(ActionEvent e) {
                btn_Clean_actionPerformed(e);
            }
        });
        btn_Clock.setBackground(Color.orange);
        btn_Clock.setFont(new java.awt.Font("Dialog", 0, 14));
        btn_Clock.setForeground(Color.magenta);
        btn_Clock.setBorder(titledBorder1);
        btn_Clock.setMnemonic('O');
        btn_Clock.setText(" 时钟(O)");
        btn_Clock.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(ActionEvent e) {
                btn_Clock_actionPerformed(e);
            }
        });
        jPanel1.setLayout(borderLayout1);
        borderLayout1.setHgap(2);
        borderLayout1.setVgap(2);
        jPanel1.setEnabled(true);
        jPanel1.add(jLabel1, BorderLayout.NORTH);
        jPanel1.add(btn_Start, BorderLayout.WEST);
        jPanel1.add(btn_Clean, BorderLayout.CENTER);
        jPanel1.add(btn_Clock, BorderLayout.EAST);//        ClockThread nowClock=new ClockThread();
    }
/*    public void start(){
        Thread clockThread;
        if(clockThread==null){
            clockThread=new java.lang.Thread(this,"Clock");
            clockThread.start();
        }
    }*/
    public static void main(String args[]){
        JFrame frame=new JFrame("nihao");
        frame.addWindowListener(new WindowAdapter(){
            public void windowClosing(WindowEvent e){
                System.exit(0);
            }
        });
        new Clock();
        frame.getContentPane().add(jPanel1,BorderLayout.CENTER );
        frame.pack();
        frame.setVisible(true);
    }    void btn_Start_actionPerformed(ActionEvent e) {
        jLabel1.setText("nihao");
        try{
        nowClock.suspend();
        }
        catch(Exception e1) {
          e1.printStackTrace();
        }
    }    void btn_Clean_actionPerformed(ActionEvent e) {
        jLabel1.setText("00:00:00");
        try{
        nowClock.suspend();
        }
        catch(Exception e1) {
          e1.printStackTrace();
        }
    }void btn_Clock_actionPerformed(ActionEvent e) {
//        ClockThread nowClock=new ClockThread();
        nowClock.setLabel(jLabel1);
        if(nowClock.isAlive()) nowClock.resume();
        else  nowClock.start();
/*        jLabel1.setText(nowClock.repaint());
        Date now=new Date();
        String s;
        s=now.getHours()+":"+now.getMinutes() +":"+now.getSeconds();
        jLabel1.setText(s);*/
    }
}class ClockThread extends Thread {
    private Thread clockTh=null;
    JLabel L;
    public  void  setLabel(JLabel L)
    {
      this.L = L;
    }
    /*
    public void start(){        if(clockTh==null){
            //clockTh=new Thread(this,"ClockThread");
            clockTh.start();
        }    }
    */
    public void run(){
        //Thread myThread=Thread.currentThread();
        //start();
        //System.out.println("currentThread = "+myThread);
        //System.out.println("this = "+this);
        //System.out.println("clockTh = "+clockTh);
        try{
            Thread.sleep(1000);
        }catch(InterruptedException e){}
        L.setText("Zhangping");
    /*        try{
                Thread.sleep(1000);
            }catch(InterruptedException e){}
            L.setText("23:59:59");*/        //while(clockTh==myThread){
          while  (true)
          {
            L.setText(repaint());
            try{
                Thread.sleep(1000);
            }catch(InterruptedException e){}
          }
           // //i//f(clockTh.getThreadGroup()!=myThread.getThreadGroup())
              //  System.out.println("Flase");
            //e//lse
               // System.out.println("True");
            //}
        }
    public String repaint(){
        String s;
        Date now=new Date();
        s=now.getHours() +":"+now.getMinutes()+":"+now.getSeconds();
        return s;
    }
}