webbrowserpane.java

java 编程源代码

// WebBrowserPane.java
// WebBrowserPane is a simple Web-browsing component that 
// extends JEditorPane and maintains a history of visited URLs.
package com.deitel.advjhtp1.gui.webbrowser;

// Java core packages
import java.util.*;
import java.net.*;
import java.io.*;

// Java extension packages
import javax.swing.*;
import javax.swing.event.*;

public class WebBrowserPane extends JEditorPane {
   
   private List history = new ArrayList();
   private int historyIndex;
   
   // WebBrowserPane constructor
   public WebBrowserPane() 
   {
      // disable editing to enable hyperlinks
      setEditable( false );
   }
   
   // display given URL and add it to history
   public void goToURL( URL url )
   { 
      displayPage( url );
      history.add( url ); 
      historyIndex = history.size() - 1;
   }
   
   // display next history URL in editorPane
   public URL forward()
   {
      historyIndex++;
      
      // do not go past end of history
      if ( historyIndex >= history.size() )
         historyIndex = history.size() - 1;
      
      URL url = ( URL ) history.get( historyIndex );
      displayPage( url );
         
      return url;
   }
   
   // display previous history URL in editorPane
   public URL back()
   {
      historyIndex--;
      
      // do not go past beginning of history
      if ( historyIndex < 0 )
         historyIndex = 0;
      
      // display previous URL
      URL url = ( URL ) history.get( historyIndex );
      displayPage( url );

      return url;      
   }
   
   // display given URL in JEditorPane
   private void displayPage( URL pageURL )
   {
      // display URL
      try {
         setPage( pageURL );
      }

      // handle exception reading from URL
      catch ( IOException ioException ) {
         ioException.printStackTrace();
      }
   }     
}