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Message:
Enjoy your java HTML browser...
Posted by Kishori Sharan on November 11, 2000 at 2:09 PM
Hi
Here is the mini HTML browser in Java. The name of the class is JavaBrowser. Compile the program and then run it. You can also pass command line parameter which is a HTML file to display in the beginning. You can also enter an internet address and it will open the webpage in the frame. I have attached the short description of the program and the code.
Thanx
Kishori
/////////////////////////////////////
Here is the description of program:
//////////////////////////////////////
1. JavaBrowser is the name of the class you will run.
It extends Jframe to show the HTML file. The JFrame contains
a panel in North and a JEditorPane in center. In panel
we have address label, address field and go button.
JavaBrowser implements HyperlinkListener so that when
user clicks on a link then we can load another page. For
HyperlinkListener interface we have implement updateHyperlink ( ) method. It also implements ActionListener so that when user
types in a new URL and clicks the GO button or hits enter key then we can load the new page.
2. In constructor of JavaBrowser I have adde3d the panel and JEditorPane described in STEP 1.
3. displayPage ( String page ) method: This method first
checks whether the string passed to this is a file name
or a URL. If it is a file name then it prefixes "file:///"
to the string and then tries to load the page else tries to
check if it is a valid URL and tries to load the page
from that URL. 4. main ( String[] args ) method: Checks if user has
provided any URL at common prompt then
passes that URL to displayPage ( String page ) method which
in turn tries to load the page. 5. hyperlinkUpdate ( ) method : This has to be implented because
JavaBrowser implements HyperlinkListener. This method
is invoked when user clicks on a link in HTML page.
6. actionPerformed: ( ) method: This method is invoked when
user hits enter in address text field or hits GO button.
This method reads the address entered by user and passes it to displayPage method to load the new page. //////////////// JavaBrowser.java //////////
import java.io.* ;
import javax.swing.* ;
import java.awt.* ;
import javax.swing.event.* ;
import java.awt.event.* ;
import java.net.URL ; public class JavaBrowser extends JFrame implements HyperlinkListener, ActionListener {
private JLabel addrLabel = new JLabel ( "Address:" ) ;
private JTextField addrText = new JTextField ( "http://www." ) ;
private JButton goButton = new JButton ( "Go" ) ;
private JEditorPane browser = new JEditorPane ( ) ; // The main HTML pane
public JavaBrowser ( ) {
// Set the title for the frame
setTitle ( "Java Browser" ) ;
// Set the position and size of frame
setBounds ( 10, 10 , 500, 500 ) ;
/* Make the JEditoPane non-editable so that when user
clicks on a link then another page is loaded. By default,
JEditorPane is editable and works as a HTML editor not as
a browser. Make make it work as a browser we must make it
non-editable */
browser.setEditable ( false ) ;
/* Add a hyperlink listener so that when user clicks on a
link then hyperlinkUpdate ( ) method is called and we
will load another page */
browser.addHyperlinkListener ( this ) ;
//Put the address text filed and button on the north of frame
JPanel panel = new JPanel ( ) ;
panel.setLayout ( new BoxLayout ( panel, BoxLayout.X_AXIS ) ) ;
panel.add ( addrLabel ) ;
panel.add ( addrText ) ;
panel.add ( goButton ) ;
// Add the action listener to button and address text field so that
// when user hits enter in address text filed or presses the Go button
// then new page is displayed
addrText.addActionListener ( this ) ;
goButton.addActionListener ( this ) ;
// Add the panel and editor pane to the frame
Container cp = getContentPane ( ) ;
// Add the panel to the north
cp.add ( panel, "North" ) ;
cp.add ( new JScrollPane ( browser, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS ) ) ;
}
public static void main ( String[] args ) {
String initPage = "" ;
JavaBrowser jb = new JavaBrowser ( ) ;
jb.show ( ) ;
// Check if user has specified any command line parameter
if ( args.length > 0 ) {
// Read the first argument
initPage = args[0] ;
// Display the page
jb.displayPage ( initPage ) ;
}
}
public void displayPage ( String page ) {
// Check if user has specified any command line parameter
if ( page != null && page.trim().length() > 0 ) {
// Set this address
addrText.setText ( page ) ;
/* User may specify one of the following
1. A relative path for a local file
2. An absolute path for a local file
3. A URL
Check for a valid user input
*/ File localFile = new File ( page ) ; // Chgeck if the file exists on the dist
if ( localFile.exists ( ) && localFile.isFile () ) {
/* Check if user specified the absolute path
Add the file protocol in front of file name */
page = "file:///" + localFile.getAbsolutePath ( ) ;
try {
browser.setPage ( page ) ;
}
catch ( Exception e1 ) {
// Not a valid URL
browser.setText ( "Could not load page:" + page + "\n" +
"Error:" + e1.getMessage ( ) ) ;
}
}
else {
// Maybe user specified a URL
try {
URL url = new URL ( page ) ;
browser.setPage ( url ) ;
}
catch ( Exception e ) {
// Not a valid URL
browser.setText ( "Could not load page:" + page + "\n" +
"Error:" + e.getMessage ( ) ) ;
} } }
else {
browser.setText ( "Could not load page:" + page ) ;
}
}
public void hyperlinkUpdate ( HyperlinkEvent e ) {
/* Get the event type for the link. There could be three types
of event generated by user actions on a link.When user's mouse
enters a link then ENTERED event is triggerd. When user clicks the
link the ACTIVATED is triggered and when user exits the link then
EXITED is triggerd. */
if ( e.getEventType ( ) == HyperlinkEvent.EventType.ACTIVATED ) {
try {
// Loads the new page represented by link clicked
URL url = e.getURL ( ) ;
browser.setPage ( url ) ;
addrText.setText ( url.toString ( ) ) ;
}
catch ( Exception exc ) {
}
}
}
public void actionPerformed ( ActionEvent e ) {
// Load the new page
String page = "" ;
try {
// Get the new url
page = addrText.getText ( ) ;
// User may eneter a file name or URL. displayPage handles both of them
displayPage ( page ) ;
}
catch ( Exception exc ) {
browser.setText ( "Page could not be loaded:" + page + "\n" +
"Error:" + exc.getMessage ( ) ) ;
}
}
}
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