communication.java

Java程序设计实验与实训源代码经典的JAVA学习教材

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.net.URL;
import java.net.MalformedURLException;

public class Communication extends Applet 
                          implements ActionListener 
{
	URLWindow urlWindow;

    public void init() 
	{
        Button button = new Button("Bring up URL window");
        button.addActionListener(this);
        add(button);
        urlWindow = new URLWindow(getAppletContext());
        urlWindow.pack();
}

    public void destroy() 
	{
        urlWindow.setVisible(false);
        urlWindow = null;
}

    public void actionPerformed(ActionEvent event) 
	{
        urlWindow.setVisible(true);
    }
}

class URLWindow extends Frame 
                implements ActionListener 
{
    TextField urlField;
    Choice choice;
AppletContext appletContext;

    public URLWindow(AppletContext appletContext) 
	{
        super("Show a Document!");
        this.appletContext = appletContext;
        GridBagLayout gridBag = new GridBagLayout();
        GridBagConstraints c = new GridBagConstraints();
        setLayout(gridBag);
        Label label1 = new Label("URL of document to show:",
				 Label.RIGHT);
        gridBag.setConstraints(label1, c);
        add(label1);
        urlField = new TextField("http://java.sun.com/", 40);
        urlField.addActionListener(this);
        c.gridwidth = GridBagConstraints.REMAINDER;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.weightx = 1.0;
        gridBag.setConstraints(urlField, c);
        add(urlField);
        Label label2 = new Label("Window/frame to show it in:",
				 Label.RIGHT);
        c.gridwidth = 1;
        c.weightx = 0.0;
        gridBag.setConstraints(label2, c);
        add(label2);
        choice = new Choice();
        choice.addItem("(browser's choice)"); 
        // 一个名称为My Personal Window窗口
		choice.addItem("My Personal Window"); 
        // 一个新的未命名的窗口
		choice.addItem("_blank");
        choice.addItem("_self"); 
        choice.addItem("_parent");
		// 包含该Applet的窗口
        choice.addItem("_top");
        c.fill = GridBagConstraints.NONE;
        c.gridwidth = GridBagConstraints.REMAINDER;
        c.anchor = GridBagConstraints.WEST;
        gridBag.setConstraints(choice, c);
        add(choice);
        Button button = new Button("Show document");
        button.addActionListener(this);
        c.weighty = 1.0;
        c.ipadx = 10;
        c.ipady = 10;
        c.insets = new Insets(5,0,0,0);
        c.anchor = GridBagConstraints.SOUTH;
        gridBag.setConstraints(button, c);
        add(button);
        addWindowListener(
			new WindowAdapter() 
			{
		        public void windowClosing(WindowEvent event) 
				{
			        setVisible(false);
				}
	        });
}     

    public void actionPerformed(ActionEvent event) 
	{
        String urlString = urlField.getText();
        URL url = null;
        try 
		{
            url = new URL(urlString);
        }
		catch (MalformedURLException e) 
		{
            System.err.println("Malformed URL: " + urlString);
        }
        if (url != null) 
		{
            if (choice.getSelectedIndex() == 0) 
			{
                appletContext.showDocument(url);
            }
			else 
			{
                appletContext.showDocument(url, 
				  choice.getSelectedItem());
            }
        }
    }
}