dataexchangetest.java

Java编程例子(全新)演示基础的Java 功能,例如类,对象的使用,过程的调用,.

/**
   @version 1.32 2004-05-05
   @author Cay Horstmann
*/

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

public class DataExchangeTest
{
   public static void main(String[] args)
   {  
      DataExchangeFrame frame = new DataExchangeFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}

/**
   A frame with a menu whose File->Connect action shows a
   password dialog.
*/
class DataExchangeFrame extends JFrame 
{  
   public DataExchangeFrame()
   {
      setTitle("DataExchangeTest");
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

      // construct a File menu
      
      JMenuBar mbar = new JMenuBar();
      setJMenuBar(mbar);
      JMenu fileMenu = new JMenu("File");
      mbar.add(fileMenu);

      // add Connect and Exit menu items

      JMenuItem connectItem = new JMenuItem("Connect");
      connectItem.addActionListener(new ConnectAction());
      fileMenu.add(connectItem);

      // The Exit item exits the program

      JMenuItem exitItem = new JMenuItem("Exit");
      exitItem.addActionListener(new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               System.exit(0);
            }
         });
      fileMenu.add(exitItem);

      textArea = new JTextArea();
      add(new JScrollPane(textArea), BorderLayout.CENTER);
   }

   public static final int DEFAULT_WIDTH = 300;
   public static final int DEFAULT_HEIGHT = 200;  

   private PasswordChooser dialog = null;
   private JTextArea textArea;

   /**
      The Connect action pops up the password dialog.
   */

   private class ConnectAction implements ActionListener
   {
      public void actionPerformed(ActionEvent event)
      {
         // if first time, construct dialog

         if (dialog == null) 
            dialog = new PasswordChooser();
         
         // set default values
         dialog.setUser(new User("yourname", null));

         // pop up dialog
         if (dialog.showDialog(DataExchangeFrame.this, "Connect"))
         {
            // if accepted, retrieve user input
            User u = dialog.getUser();
            textArea.append(
               "user name = " + u.getName()
               + ", password = " + (new String(u.getPassword()))
               + "\n");
         }
      }
   }
}

/**
   A password chooser that is shown inside a dialog
*/
class PasswordChooser extends JPanel 
{  
   public PasswordChooser()
   {  
      setLayout(new BorderLayout());

      // construct a panel with user name and password fields

      JPanel panel = new JPanel();
      panel.setLayout(new GridLayout(2, 2));
      panel.add(new JLabel("User name:"));
      panel.add(username = new JTextField(""));
      panel.add(new JLabel("Password:"));
      panel.add(password = new JPasswordField(""));
      add(panel, BorderLayout.CENTER);

      // create Ok and Cancel buttons that terminate the dialog
      
      okButton = new JButton("Ok");
      okButton.addActionListener(new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               ok = true;
               dialog.setVisible(false);
            }
         });

      JButton cancelButton = new JButton("Cancel");
      cancelButton.addActionListener(new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               dialog.setVisible(false);
            }
         });

      // add buttons to southern border

      JPanel buttonPanel = new JPanel();
      buttonPanel.add(okButton);
      buttonPanel.add(cancelButton);
      add(buttonPanel, BorderLayout.SOUTH);
   }

   /**
      Sets the dialog defaults.
      @param u the default user information
   */
   public void setUser(User u)
   {
      username.setText(u.getName());
   }

   /**
      Gets the dialog entries.
      @return a User object whose state represents 
      the dialog entries
   */
   public User getUser()
   {
      return new User(username.getText(), password.getPassword());
   }

   /**
      Show the chooser panel in a dialog
      @param parent a component in the owner frame or null
      @param title the dialog window title
   */
   public boolean showDialog(Component parent, String title)
   {  
      ok = false;

      // locate the owner frame

      Frame owner = null;
      if (parent instanceof Frame)
         owner = (Frame) parent;
      else 
         owner = (Frame) SwingUtilities.getAncestorOfClass(Frame.class, parent);

      // if first time, or if owner has changed, make new dialog
      
      if (dialog == null || dialog.getOwner() != owner) 
      {      
         dialog = new JDialog(owner, true);
         dialog.add(this);
         dialog.getRootPane().setDefaultButton(okButton);
         dialog.pack();
      }

      // set title and show dialog

      dialog.setTitle(title);
      dialog.setVisible(true);
      return ok;
   }

   private JTextField username;
   private JPasswordField password;
   private JButton okButton;
   private boolean ok;
   private JDialog dialog;
}

/**
   A user has a name and password. For security reasons, the 
   password is stored as a char[], not a String.
*/
class User
{
   public User(String aName, char[] aPassword)
   {
      name = aName;
      password = aPassword;
   }
   
   public String getName() { return name; }
   public char[] getPassword() { return password; }

   public void setName(String aName) { name = aName; }
   public void setPassword(char[] aPassword) { password = aPassword; }

   private String name;
   private char[] password;
}