问让JButtons在每个循环周期中刷新标签

EN

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class GeorgeBridge extends JApplet implements ActionListener{
  // Create a frame to hold the contents of application
  JFrame frame = new JFrame ("George's Big Bridge Crossing");

  // Panel to hold the bridge
  JPanel bridgePanel = new JPanel(new GridLayout(1,7));

  /* The following JLabels are used for spacing of the panels in the frame to make the window look more like a bridge 
   * crossing over a river
   */
  JLabel northLabel = new JLabel(" ");
  JLabel eastLabel = new JLabel("         ");
  JLabel westLabel = new JLabel("         ");
  // Asks the user whether or not they would like George to cross the bridge
  JLabel southLabel = new JLabel("Would you like George to cross the Bridge?"); 

  // George is represented by a red X
  String george = "X";

  // An array of 7 JButtons to act as the bridge
  JButton [] bridge = new JButton [7];

  int spot;





  public void init() { 
    bridge[0] = new JButton ("");
    bridge[1] = new JButton ("");
    bridge[2] = new JButton ("");
    bridge[3] = new JButton ("");
    bridge[4] = new JButton ("");
    bridge[5] = new JButton ("");
    bridge[6] = new JButton ("");



    // Set the program to exit when the JFrame is closed
    frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    //set a border layout manager to the frame
    frame.setLayout(new BorderLayout());

    // Background set to look like water under the bridge
    bridgePanel.setBackground (new Color(0,191,246));

    // Panel to make it look like the bridge is crossing a river
    JPanel northPanel = new JPanel();
    northPanel.setBackground (new Color (0,191,246));

    // Panel to make it look like the bridge is crossing a river
    JPanel eastPanel = new JPanel();
    eastPanel.setBackground (new Color (0,184,48));

    // Panel to make it look like the bridge is crossing a river
    JPanel southPanel = new JPanel();
    southPanel.setBackground (new Color (0,191,246));

    // Panel to make it look like the bridge is crossing a river
    JPanel westPanel = new JPanel();
    westPanel.setBackground (new Color(0,184,48));

    // JButton to let the user choose when George crosses the bridge
    JButton cross = new JButton("Make George cross!");
    cross.setActionCommand("cross");
    cross.addActionListener(this);   

    // Starts George standing on the West Bank
    westLabel.setText(george);
    // Makes George red so he is more visible
    westLabel.setForeground(new Color(255,0,0));
    // Makes George size 24 font so he is more visible
    westLabel.setFont(westPanel.getFont().deriveFont(24.0f));

    // Initiates the first button that represents a foot of the bridge
//    bridge[0] = new JButton ("");
    bridge[0].setBackground(new Color(143,66,19));// Set the background to a brown to make the bridge look like a wooden bridge
    bridge[0].setForeground(new Color(255,0,0));// Set the colour of George to red
    bridge[0].setFont(bridge[0].getFont().deriveFont(24.0f));// Set the font for George to 24

    // Initiates the second button that represents a foot of the bridge
//    bridge[1] = new JButton ("");
    bridge[1].setBackground(new Color(143,66,19));// Set the background to a brown to make the bridge look like a wooden bridge
    bridge[1].setForeground(new Color(255,0,0));// Set the colour of George to red
    bridge[1].setFont(bridge[0].getFont().deriveFont(24.0f));// Set the font for George to 24

    // Initiates the third button that represents a foot of the bridge
//    bridge[2] = new JButton ("");
    bridge[2].setBackground(new Color(143,66,19));// Set the background to a brown to make the bridge look like a wooden bridge
    bridge[2].setForeground(new Color(255,0,0));// Set the colour of George to red
    bridge[2].setFont(bridge[0].getFont().deriveFont(24.0f));// Set the font for George to 24

    // Initiates the fourth button that represents a foot of the bridge
//    bridge[3] = new JButton ("");
    bridge[3].setBackground(new Color(143,66,19));// Set the background to a brown to make the bridge look like a wooden bridge
    bridge[3].setForeground(new Color(255,0,0));// Set the colour of George to red
    bridge[3].setFont(bridge[0].getFont().deriveFont(24.0f));// Set the font for George to 24

    // Initiates the fifth button that represents a foot of the bridge
//    bridge[4] = new JButton ("");
    bridge[4].setBackground(new Color(143,66,19));// Set the background to a brown to make the bridge look like a wooden bridge
    bridge[4].setForeground(new Color(255,0,0));// Set the colour of George to red
    bridge[4].setFont(bridge[0].getFont().deriveFont(24.0f));// Set the font for George to 24

    // Initiates the sixth button that represents a foot of the bridge
//    bridge[5] = new JButton ("");
    bridge[5].setBackground(new Color(143,66,19));// Set the background to a brown to make the bridge look like a wooden bridge
    bridge[5].setForeground(new Color(255,0,0));// Set the colour of George to red
    bridge[5].setFont(bridge[0].getFont().deriveFont(24.0f));// Set the font for George to 24

    // Initiates the seventh button that represents a foot of the bridge
//    bridge[6] = new JButton ("");
    bridge[6].setBackground(new Color(143,66,19));// Set the background to a brown to make the bridge look like a wooden bridge
    bridge[6].setForeground(new Color(255,0,0));// Set the colour of George to red
    bridge[6].setFont(bridge[0].getFont().deriveFont(24.0f));// Set the font for George to 24

    // Add the bridge buttons to the bridge panel
    bridgePanel.add(bridge[0]);
    bridgePanel.add(bridge[1]);
    bridgePanel.add(bridge[2]);
    bridgePanel.add(bridge[3]);
    bridgePanel.add(bridge[4]);
    bridgePanel.add(bridge[5]);
    bridgePanel.add(bridge[6]);

    // Add the labels and buttons to the 4 border panels
    northPanel.add(northLabel);
    eastPanel.add(eastLabel);
    southPanel.add(southLabel);
    southPanel.add(cross);
    westPanel.add(westLabel);

    // Add all the panels to the JFrame
    frame.getContentPane().add(northPanel, BorderLayout.NORTH);
    frame.getContentPane().add(eastPanel, BorderLayout.EAST);
    frame.getContentPane().add(bridgePanel, BorderLayout.CENTER);
    frame.getContentPane().add(southPanel, BorderLayout.SOUTH);
    frame.getContentPane().add(westPanel, BorderLayout.WEST);

    // Set the JFrame size and visibility
    frame.setSize(450,150);
    frame.setVisible(true);
  }

  public void actionPerformed (ActionEvent event) {

    new Thread (new Runnable() {
      public void run() {
        moveGeorge();
      }
    }).start();
  }

  public void moveGeorge() {
    for(int i=0; i<7; i++) {
      spot = i;
      SwingUtilities.invokeLater(new Runnable() {
        public void run() {
          if (spot > 0) {
            bridge[spot].setText(george);
            bridge[spot-1].setText("");
          }
          else {
            westLabel.setText("");
            bridge[spot].setText(george);
          }

          try
        {
          Thread.sleep(1000); // do nothing for 1000 miliseconds (1 second)
        }
        catch(InterruptedException e)
        {
          e.printStackTrace();
        }

          frame.setVisible(true);
        }
      });
    }
  }
}