FileDocCategorySizeDatePackage
Listen.javaAPI DocExample4039Mon Nov 09 12:45:52 GMT 1998None

Listen

public class Listen extends JFrame implements UndoableEditListener, DocumentListener

Fields Summary
private UndoableEdit
edit
private JTextArea
editor
private JTextArea
log
private JMenuItem
undoItem
private JMenuItem
redoItem
Constructors Summary
public Listen()


    // TextArea for entering text & generating events
    editor = new JTextArea();
    editor.getDocument().addDocumentListener(this);
    editor.getDocument().addUndoableEditListener(this);

    // TextArea for showing each event as it is fired
    log = new JTextArea();
    log.setEditable(false);

    // Lay out the frame
    JScrollPane scroll1 = new JScrollPane(editor);
    JScrollPane scroll2 = new JScrollPane(log);
    getContentPane().setLayout(new GridLayout(2,1));
    getContentPane().add(scroll1);
    getContentPane().add(scroll2);

    // Add a menu with undo/redo options (just for the most recent edit to keep
    // things simple)
    JMenuBar bar = new JMenuBar();
    JMenu menu = new JMenu("Edit");
    undoItem = new JMenuItem("Undo");
    redoItem = new JMenuItem("Redo");
    bar.add(menu);
    menu.add(undoItem);
    menu.add(redoItem);
    updateMenu();

    // Call edit.undo() and update menu when undo is selected
    undoItem.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent ev) {
        edit.undo();
        updateMenu();
      }
    });

    // Call edit.redo() and update menu when redo is selected
    redoItem.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent ev) {
        edit.redo();
        updateMenu();
      }
    });
    setJMenuBar(bar);
    setSize(410, 400);
Methods Summary
public voidchangedUpdate(javax.swing.event.DocumentEvent ev)

    showDocEvent(ev);
public voidinsertUpdate(javax.swing.event.DocumentEvent ev)

    showDocEvent(ev);
public static voidmain(java.lang.String[] args)

    JFrame f = new Listen();
    f.addWindowListener(new BasicWindowMonitor());
    f.setVisible(true);
public voidremoveUpdate(javax.swing.event.DocumentEvent ev)

    showDocEvent(ev);
protected voidshowDocEvent(javax.swing.event.DocumentEvent ev)

    StringBuffer buf = new StringBuffer(100);
    buf.append(ev.getType());
    buf.append(" offset:");
    buf.append(ev.getOffset());
    buf.append(" length:");
    buf.append(ev.getLength());

    // Show any ElementChanges that were provided
    Element root = editor.getDocument().getDefaultRootElement();
    DocumentEvent.ElementChange chg = ev.getChange(root);
    if (chg == null) {
      buf.append(" <NO ELEMENT CHANGES>");
    }
    else {
      buf.append(" Changes (Index/Add/Rem):");
      buf.append(chg.getIndex());
      buf.append("/");
      buf.append(chg.getChildrenAdded().length);
      buf.append("/");
      buf.append(chg.getChildrenRemoved().length);
    }
    buf.append("\n");
    log.append(buf.toString());
public voidundoableEditHappened(javax.swing.event.UndoableEditEvent ev)

    StringBuffer buf = new StringBuffer(100);
    edit = ev.getEdit();
    buf.append("UndoableEdit:");
    buf.append(edit.getPresentationName());
    buf.append("\n");
    log.append(buf.toString());
    updateMenu();
protected voidupdateMenu()

    if (edit != null) {
      undoItem.setEnabled(edit.canUndo());
      redoItem.setEnabled(edit.canRedo());
      undoItem.setText(edit.getUndoPresentationName());
      redoItem.setText(edit.getRedoPresentationName());
    }
    else {
      undoItem.setEnabled(false);
      redoItem.setEnabled(false);
      undoItem.setText("Undo");
      redoItem.setText("Redo");
    }