MiniBrowser FilesHEADmaster

2 files changed, 242 insertions, 0 deletions

diff --git a/MiniBrowser.class b/MiniBrowser.class
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+++ b/MiniBrowser.class
diff --git a/MiniBrowser.java b/MiniBrowser.java
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+++ b/MiniBrowser.java
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+import java.awt.*;
+import java.awt.event.*;
+import java.net.*;
+import java.util.*;
+import javax.swing.*;
+import javax.swing.event.*;
+import javax.swing.text.html.*;
+ 
+// The Simple Web Browser.
+public class MiniBrowser extends JFrame
+         
+        implements HyperlinkListener {
+    // These are the buttons for iterating through the page list.
+    private JButton backButton, forwardButton;
+     
+    // Page location text field.
+    private JTextField locationTextField;
+     
+    // Editor pane for displaying pages.
+    private JEditorPane displayEditorPane;
+     
+    // Browser's list of pages that have been visited.
+    private ArrayList pageList = new ArrayList();
+     
+    // Constructor for Mini Web Browser.
+    public MiniBrowser() {
+        // Set application title.
+        super("Mini Browser");
+         
+        // Set window size.
+        setSize(640, 480);
+         
+        // Handle closing events.
+        addWindowListener(new WindowAdapter() {
+            public void windowClosing(WindowEvent e) {
+                actionExit();
+            }
+        });
+         
+        // Set up file menu.
+        JMenuBar menuBar = new JMenuBar();
+        JMenu fileMenu = new JMenu("File");
+        fileMenu.setMnemonic(KeyEvent.VK_F);
+        JMenuItem fileExitMenuItem = new JMenuItem("Exit",
+                KeyEvent.VK_X);
+        fileExitMenuItem.addActionListener(new ActionListener() {
+            public void actionPerformed(ActionEvent e) {
+                actionExit();
+            }
+        });
+        fileMenu.add(fileExitMenuItem);
+        menuBar.add(fileMenu);
+        setJMenuBar(menuBar);
+         
+        // Set up button panel.
+        JPanel buttonPanel = new JPanel();
+        backButton = new JButton("< Back");
+        backButton.addActionListener(new ActionListener() {
+            public void actionPerformed(ActionEvent e) {
+                actionBack();
+            }
+        });
+        backButton.setEnabled(false);
+        buttonPanel.add(backButton);
+        forwardButton = new JButton("Forward >");
+        forwardButton.addActionListener(new ActionListener() {
+            public void actionPerformed(ActionEvent e) {
+                actionForward();
+            }
+        });
+        forwardButton.setEnabled(false);
+        buttonPanel.add(forwardButton);
+        locationTextField = new JTextField(35);
+        locationTextField.addKeyListener(new KeyAdapter() {
+            public void keyReleased(KeyEvent e) {
+                if (e.getKeyCode() == KeyEvent.VK_ENTER) {
+                    actionGo();
+                }
+            }
+        });
+        buttonPanel.add(locationTextField);
+        JButton goButton = new JButton("GO");
+        goButton.addActionListener(new ActionListener() {
+            public void actionPerformed(ActionEvent e) {
+                actionGo();
+            }
+        });
+        buttonPanel.add(goButton);
+         
+        // Set up page display.
+        displayEditorPane = new JEditorPane();
+        displayEditorPane.setContentType("text/html");
+        displayEditorPane.setEditable(false);
+        displayEditorPane.addHyperlinkListener(this);
+         
+        getContentPane().setLayout(new BorderLayout());
+        getContentPane().add(buttonPanel, BorderLayout.NORTH);
+        getContentPane().add(new JScrollPane(displayEditorPane),
+                BorderLayout.CENTER);
+    }
+     
+    // Exit this program.
+    private void actionExit() {
+        System.exit(0);
+    }
+     
+    // Go back to the page viewed before the current page.
+    private void actionBack() {
+        URL currentUrl = displayEditorPane.getPage();
+ 
+        int pageIndex = pageList.indexOf(currentUrl.toString());
+        try {
+            showPage(
+                    new URL((String) pageList.get(pageIndex - 1)), false);
+        } catch (Exception e) {}
+    }
+     
+    // Go forward to the page viewed after the current page.
+    private void actionForward() {
+        URL currentUrl = displayEditorPane.getPage();
+        int pageIndex = pageList.indexOf(currentUrl.toString());
+        try {
+            showPage(
+                    new URL((String) pageList.get(pageIndex + 1)), false);
+        } catch (Exception e) {}
+    }
+     
+    // Load and show the page specified in the location text field.
+    private void actionGo() {
+        URL verifiedUrl = verifyUrl(locationTextField.getText());
+        if (verifiedUrl != null) {
+            showPage(verifiedUrl, true);
+        } else {
+            showError("Invalid URL");
+        }
+    }
+     
+    // Show dialog box with error message.
+    private void showError(String errorMessage) {
+        JOptionPane.showMessageDialog(this, errorMessage,
+                "Error", JOptionPane.ERROR_MESSAGE);
+    }
+     
+    // Verify URL format.
+    private URL verifyUrl(String url) {
+        // Only allow HTTP URLs.
+        if (!url.toLowerCase().startsWith("http://"))
+            return null;
+         
+        // Verify format of URL.
+        URL verifiedUrl = null;
+        try {
+            verifiedUrl = new URL(url);
+        } catch (Exception e) {
+            return null;
+        }
+         
+        return verifiedUrl;
+    }
+     
+  /* Show the specified page and add it to
+     the page list if specified. */
+    private void showPage(URL pageUrl, boolean addToList) {
+        // Show hour glass cursor while crawling is under way.
+        setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
+         
+        try {
+            // Get URL of page currently being displayed.
+            URL currentUrl = displayEditorPane.getPage();
+             
+            // Load and display specified page.
+            displayEditorPane.setPage(pageUrl);
+             
+            // Get URL of new page being displayed.
+            URL newUrl = displayEditorPane.getPage();
+             
+            // Add page to list if specified.
+            if (addToList) {
+                int listSize = pageList.size();
+                if (listSize > 0) {
+                    int pageIndex =
+                            pageList.indexOf(currentUrl.toString());
+                    if (pageIndex < listSize - 1) {
+                        for (int i = listSize - 1; i > pageIndex; i--) {
+                            pageList.remove(i);
+                        }
+                    }
+                }
+                pageList.add(newUrl.toString());
+            }
+             
+            // Update location text field with URL of current page.
+            locationTextField.setText(newUrl.toString());
+             
+            // Update buttons based on the page being displayed.
+            updateButtons();
+        } catch (Exception e) {
+            // Show error messsage.
+            showError("Unable to load page");
+        } finally {
+            // Return to default cursor.
+            setCursor(Cursor.getDefaultCursor());
+        }
+    }
+     
+  /* Update back and forward buttons based on
+     the page being displayed. */
+    private void updateButtons() {
+        if (pageList.size() < 2) {
+            backButton.setEnabled(false);
+            forwardButton.setEnabled(false);
+        } else {
+            URL currentUrl = displayEditorPane.getPage();
+            int pageIndex = pageList.indexOf(currentUrl.toString());
+            backButton.setEnabled(pageIndex > 0);
+            forwardButton.setEnabled(
+                    pageIndex < (pageList.size() - 1));
+        }
+    }
+     
+    // Handle hyperlink's being clicked.
+    public void hyperlinkUpdate(HyperlinkEvent event) {
+        HyperlinkEvent.EventType eventType = event.getEventType();
+        if (eventType == HyperlinkEvent.EventType.ACTIVATED) {
+            if (event instanceof HTMLFrameHyperlinkEvent) {
+                HTMLFrameHyperlinkEvent linkEvent =
+                        (HTMLFrameHyperlinkEvent) event;
+                HTMLDocument document =
+                        (HTMLDocument) displayEditorPane.getDocument();
+                document.processHTMLFrameHyperlinkEvent(linkEvent);
+            } else {
+                showPage(event.getURL(), true);
+            }
+        }
+    }
+     
+    // Run the Mini Browser.
+    public static void main(String[] args) {
+        MiniBrowser browser = new MiniBrowser();
+        browser.show();
+    }
+}
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