恐怕还是面板布局的问题。谢谢。

Question

relive(六道轮回，无想转生)
再给指导指导。

Answer 1

构造方法中第一个下面的语句改为：
constraints.fill = GridBagConstraints.BOTH;
即可。

Answer 2

/* 
 *@(#)Traffic5.java  1.5  2003/03/28
 *
 * Copyright (c) Since 2003 WisdomLeague  
 * JRT 1.4.1
 */
/**
 *
 *@version      1.5   28 March 2003
 *@author   Fan
 */ import javax.swing.*;
 import java.awt.*;
 import java.awt.event.*; public class Traffic5 extends JFrame {
     public int num = 0;      
     Traffic5() {
         super("Traffic");
         setSize(100,410);
         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 GridBagLayout gridbag = new GridBagLayout();
 GridBagConstraints constraints = new GridBagConstraints();
 JPanel pane = new JPanel();
 pane.setLayout(gridbag);
         setContentPane(pane);         buildConstraints(constraints, 0, 1, 1, 1, 100,75);
 constraints.fill = GridBagConstraints.NONE;
 constraints.anchor = GridBagConstraints.CENTER;
 TrafficLights tl = new TrafficLights();
         tl.setPreferredSize(new Dimension(100,300));
         gridbag.setConstraints(tl, constraints);
 pane.add(tl);
         
         buildConstraints(constraints, 0, 2, 1, 1, 100, 0);
 constraints.fill = GridBagConstraints.NONE;
 constraints.anchor = GridBagConstraints.CENTER;
 TrafficButtons tb = new TrafficButtons();
 gridbag.setConstraints(tb, constraints);         
         pane.add(tb);             
    }    void buildConstraints(GridBagConstraints gbc, int gx, int gy, int gw, int gh, int wx, int wy) {
gbc.gridx = gx;
gbc.gridy = gy;
gbc.gridwidth = gw;
gbc.gridheight = gh;
gbc.weightx = wx;
gbc.weighty = wy;
    }
     public static void main (String[] arg) {
         Traffic5 tr = new Traffic5();
         tr.show();
     }
 //}     class TrafficLights extends JPanel implements Runnable {
         //public int num = 0;
         Thread runner;         public TrafficLights () {
             
             if (runner == null) {
                runner = new Thread(this);
                runner.start();
             }
         }
 
         public void run() {
             while (true) {
                 repaint();
                 try {
                     Thread.sleep(100);
                 } catch (InterruptedException e) { }
             }
         }         public void paintComponent(Graphics comp) {
             Graphics2D comp2D = (Graphics2D)comp;
             comp2D.setColor(Color.black);
             comp2D.fillRect(0, 0, 300, 300);
             if (num == 1)
                 comp2D.setColor(Color.green);
             else
                 comp2D.setColor(Color.black);
                 comp2D.fillOval(0, 0, 100, 100);
             if (num == 2)
                 comp2D.setColor(Color.yellow);
             else
                 comp2D.setColor(Color.black);
                 comp2D.fillOval(0, 100, 100, 100);
             if (num == 3)
                 comp2D.setColor(Color.red);
             else
                 comp2D.setColor(Color.black);
                 comp2D.fillOval(0, 200, 100, 100);
         }
     }
      class TrafficButtons extends JPanel implements ActionListener {
         //public int num = 0;         JButton green = new JButton("Green");
         JButton yellow = new JButton("Yellow");
         JButton red = new JButton("Red");         TrafficButtons () {
             green.addActionListener(this);
             yellow.addActionListener(this);
             red.addActionListener(this);             GridLayout family = new GridLayout(3,1,1,1);
             setLayout(family);             add(green);
             add(yellow);
             add(red);
         }         public void actionPerformed(ActionEvent evt) {
             Object src = evt.getSource();             if ( src == green )
                 num = 1;
             else if ( src == yellow )
                 num = 2;
             else if ( src == red )
                 num = 3;
         }
     }
 }
 /*好了
 */