package dataExchange;import java.awt.*;
import javax.swing.*;/*** @version 1.34 2015-06-12* @author Cay Horstmann*/
public class DataExchangeTest
{public static void main(String[] args){EventQueue.invokeLater(() -> {JFrame frame = new DataExchangeFrame();frame.setTitle("DataExchangeTest");frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setVisible(true);});}
}

package dataExchange;import java.awt.*;
import java.awt.event.*;
import javax.swing.*;/*** A frame with a menu whose File->Connect action shows a password dialog.*/
public class DataExchangeFrame extends JFrame
{public static final int TEXT_ROWS = 20;public static final int TEXT_COLUMNS = 40;private PasswordChooser dialog = null;private JTextArea textArea;public DataExchangeFrame(){// 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(event -> System.exit(0));fileMenu.add(exitItem);textArea = new JTextArea(TEXT_ROWS, TEXT_COLUMNS);add(new JScrollPane(textArea), BorderLayout.CENTER);pack();}/*** The Connect action pops up the password dialog.*/private class ConnectAction implements ActionListener{public void actionPerformed(ActionEvent event){// if first time, construct dialogif (dialog == null) dialog = new PasswordChooser();// set default valuesdialog.setUser(new User("yourname", null));// pop up dialogif (dialog.showDialog(DataExchangeFrame.this, "Connect")){// if accepted, retrieve user inputUser u = dialog.getUser();textArea.append("user name = " + u.getName() + ", password = "+ (new String(u.getPassword())) + "\n");}}}
}

package dataExchange;import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Frame;
import java.awt.GridLayout;import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;/*** A password chooser that is shown inside a dialog*/
public class PasswordChooser extends JPanel
{private JTextField username;private JPasswordField password;private JButton okButton;private boolean ok;private JDialog dialog;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(event -> {ok = true;dialog.setVisible(false);});JButton cancelButton = new JButton("Cancel");cancelButton.addActionListener(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;elseowner = (Frame) SwingUtilities.getAncestorOfClass(Frame.class, parent);// if first time, or if owner has changed, make new dialogif (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;}
}

package dataExchange;import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Frame;
import java.awt.GridLayout;import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;/*** A password chooser that is shown inside a dialog*/
public class PasswordChooser extends JPanel
{private JTextField username;private JPasswordField password;private JButton okButton;private boolean ok;private JDialog dialog;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(event -> {ok = true;dialog.setVisible(false);});JButton cancelButton = new JButton("Cancel");cancelButton.addActionListener(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;elseowner = (Frame) SwingUtilities.getAncestorOfClass(Frame.class, parent);// if first time, or if owner has changed, make new dialogif (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;}
}

负责程序：12-19。该程序主要是进行了数据的交换，使用对话框最通常的目的是获取用户的输人信息。在前面已经看到，构造对话框对象非常简单；首先初始化数据，然后调用 set Visible（true）就会在屏幕上显示对话框。                                         

 (图1) 

图2所示的对话框，可以用来获得用户名和用户密码以便连接某些在线服务。                                    

（图2）

对话框应该提供设置默认数据的方法。例如，示例程序中的 Passwordchooser类提供了一个 setuser方法，用来将默认值放到下面的字段中:

public vold setuser(User u){

    username, settext(u, getname 0);

}         

一但设置了默认值（如果需要）就可以调用 setvisible（true）让对话框显示在屏幕上。然后用户输入信息，点击OK或者 Cancel按钮。这两个按钮的事件处理器都会调用set Visible（ false）终止对 set Visible（true）的调用。另外，用户也可以选择关闭对话框。如果没有为对话框安装窗口监听器，就会执行默认的窗口结東操作，即对话框变为不可见，这也中止了对 setvisible（ue）的调用。    重要的问题是在用户解除这个对话框之前，一直调用 setvisible（true）阻塞。这样易于实现模式对话框。希望知道用户是接收对话框，还是取消对话框。在示例代码中设置了OK标志，在对话框显示之前是 false。只有OK按钮的事件处理器可以将它设置为tnue。这样，就可以获得对话框中的用户输入。