DocumentListener and DocumentEvent : DocumentListener « Swing Event « Java Tutorial






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 *     from this software without specific prior written permission.
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 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 */

/*
 * DocumentEventDemo.java requires no other files.
 */

import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.Document;

public class DocumentEventDemo extends JPanel implements ActionListener {
  JTextField textField;
  JTextArea textArea;
  JTextArea displayArea;

  public DocumentEventDemo() {
    super(new GridBagLayout());
    GridBagLayout gridbag = (GridBagLayout) getLayout();
    GridBagConstraints c = new GridBagConstraints();

    JButton button = new JButton("Clear");
    button.addActionListener(this);

    textField = new JTextField(20);
    textField.addActionListener(new MyTextActionListener());
    textField.getDocument().addDocumentListener(new MyDocumentListener());
    textField.getDocument().putProperty("name", "Text Field");

    textArea = new JTextArea();
    textArea.getDocument().addDocumentListener(new MyDocumentListener());
    textArea.getDocument().putProperty("name", "Text Area");

    JScrollPane scrollPane = new JScrollPane(textArea);
    scrollPane.setPreferredSize(new Dimension(200, 75));

    displayArea = new JTextArea();
    displayArea.setEditable(false);
    JScrollPane displayScrollPane = new JScrollPane(displayArea);
    displayScrollPane.setPreferredSize(new Dimension(200, 75));

    c.gridx = 0;
    c.gridy = 0;
    c.weightx = 1.0;
    c.fill = GridBagConstraints.HORIZONTAL;
    gridbag.setConstraints(textField, c);
    add(textField);

    c.gridx = 0;
    c.gridy = 1;
    c.weightx = 0.0;
    c.gridheight = 2;
    c.fill = GridBagConstraints.BOTH;
    gridbag.setConstraints(scrollPane, c);
    add(scrollPane);

    c.gridx = 1;
    c.gridy = 0;
    c.weightx = 1.0;
    c.weighty = 1.0;
    gridbag.setConstraints(displayScrollPane, c);
    add(displayScrollPane);

    c.gridx = 1;
    c.gridy = 2;
    c.weightx = 0.0;
    c.gridheight = 1;
    c.weighty = 0.0;
    c.fill = GridBagConstraints.HORIZONTAL;
    gridbag.setConstraints(button, c);
    add(button);

    setPreferredSize(new Dimension(450, 250));
    setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
  }

  class MyDocumentListener implements DocumentListener {
    final String newline = "\n";

    public void insertUpdate(DocumentEvent e) {
      updateLog(e, "inserted into");
    }

    public void removeUpdate(DocumentEvent e) {
      updateLog(e, "removed from");
    }

    public void changedUpdate(DocumentEvent e) {
      // Plain text components don't fire these events.
    }

    public void updateLog(DocumentEvent e, String action) {
      Document doc = (Document) e.getDocument();
      int changeLength = e.getLength();
      displayArea.append(changeLength + " character"
          + ((changeLength == 1) ? " " : "s ") + action + " "
          + doc.getProperty("name") + "." + newline + "  Text length = "
          + doc.getLength() + newline);
      displayArea.setCaretPosition(displayArea.getDocument().getLength());
    }
  }

  class MyTextActionListener implements ActionListener {
    /** Handle the text field Return. */
    public void actionPerformed(ActionEvent e) {
      int selStart = textArea.getSelectionStart();
      int selEnd = textArea.getSelectionEnd();

      textArea.replaceRange(textField.getText(), selStart, selEnd);
      textField.selectAll();
    }
  }

  /** Handle button click. */
  public void actionPerformed(ActionEvent e) {
    displayArea.setText("");
    textField.requestFocus();
  }

  /**
   * Create the GUI and show it. For thread safety, this method should be
   * invoked from the event-dispatching thread.
   */
  private static void createAndShowGUI() {
    // Create and set up the window.
    JFrame frame = new JFrame("DocumentEventDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Create and set up the content pane.
    JComponent newContentPane = new DocumentEventDemo();
    newContentPane.setOpaque(true); // content panes must be opaque
    frame.setContentPane(newContentPane);

    // Display the window.
    frame.pack();
    frame.setVisible(true);
  }

  public static void main(String[] args) {
    // Schedule a job for the event-dispatching thread:
    // creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
      public void run() {
        createAndShowGUI();
      }
    });
  }
}








15.13.DocumentListener
15.13.1.How to Write a Document ListenerHow to Write a Document Listener
15.13.2.Get document from DocumentListener
15.13.3.Listening to JTextField Events with a DocumentListenerListening to JTextField Events with a DocumentListener
15.13.4.DocumentListener and DocumentEvent