KeyListener and KeyEvent : KeyListener « Swing Event « Java Tutorial






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/*
 * KeyEventDemo
 */

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class KeyEventDemo extends JFrame implements KeyListener, ActionListener {
  JTextArea displayArea;
  JTextField typingArea;
  static final String newline = System.getProperty("line.separator");

  public static void main(String[] args) {
    /* Use an appropriate Look and Feel */
    try {
      // UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
      // UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
      UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
    } catch (UnsupportedLookAndFeelException ex) {
      ex.printStackTrace();
    } catch (IllegalAccessException ex) {
      ex.printStackTrace();
    } catch (InstantiationException ex) {
      ex.printStackTrace();
    } catch (ClassNotFoundException ex) {
      ex.printStackTrace();
    }
    /* Turn off metal's use of bold fonts */
    UIManager.put("swing.boldMetal", Boolean.FALSE);

    // Schedule a job for event dispatch thread:
    // creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
      public void run() {
        createAndShowGUI();
      }
    });
  }

  /**
   * 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.
    KeyEventDemo frame = new KeyEventDemo("KeyEventDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Set up the content pane.
    frame.addComponentsToPane();

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

  private void addComponentsToPane() {

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

    typingArea = new JTextField(20);
    typingArea.addKeyListener(this);

    // Uncomment this if you wish to turn off focus
    // traversal. The focus subsystem consumes
    // focus traversal keys, such as Tab and Shift Tab.
    // If you uncomment the following line of code, this
    // disables focus traversal and the Tab events will
    // become available to the key event listener.
    // typingArea.setFocusTraversalKeysEnabled(false);

    displayArea = new JTextArea();
    displayArea.setEditable(false);
    JScrollPane scrollPane = new JScrollPane(displayArea);
    scrollPane.setPreferredSize(new Dimension(375, 125));

    getContentPane().add(typingArea, BorderLayout.PAGE_START);
    getContentPane().add(scrollPane, BorderLayout.CENTER);
    getContentPane().add(button, BorderLayout.PAGE_END);
  }

  public KeyEventDemo(String name) {
    super(name);
  }

  /** Handle the key typed event from the text field. */
  public void keyTyped(KeyEvent e) {
    displayInfo(e, "KEY TYPED: ");
  }

  /** Handle the key pressed event from the text field. */
  public void keyPressed(KeyEvent e) {
    displayInfo(e, "KEY PRESSED: ");
  }

  /** Handle the key released event from the text field. */
  public void keyReleased(KeyEvent e) {
    displayInfo(e, "KEY RELEASED: ");
  }

  /** Handle the button click. */
  public void actionPerformed(ActionEvent e) {
    // Clear the text components.
    displayArea.setText("");
    typingArea.setText("");

    // Return the focus to the typing area.
    typingArea.requestFocusInWindow();
  }

  /*
   * We have to jump through some hoops to avoid trying to print non-printing
   * characters such as Shift. (Not only do they not print, but if you put them
   * in a String, the characters afterward won't show up in the text area.)
   */
  private void displayInfo(KeyEvent e, String keyStatus) {

    // You should only rely on the key char if the event
    // is a key typed event.
    int id = e.getID();
    String keyString;
    if (id == KeyEvent.KEY_TYPED) {
      char c = e.getKeyChar();
      keyString = "key character = '" + c + "'";
    } else {
      int keyCode = e.getKeyCode();
      keyString = "key code = " + keyCode + " (" + KeyEvent.getKeyText(keyCode)
          + ")";
    }

    int modifiersEx = e.getModifiersEx();
    String modString = "extended modifiers = " + modifiersEx;
    String tmpString = KeyEvent.getModifiersExText(modifiersEx);
    if (tmpString.length() > 0) {
      modString += " (" + tmpString + ")";
    } else {
      modString += " (no extended modifiers)";
    }

    String actionString = "action key? ";
    if (e.isActionKey()) {
      actionString += "YES";
    } else {
      actionString += "NO";
    }

    String locationString = "key location: ";
    int location = e.getKeyLocation();
    if (location == KeyEvent.KEY_LOCATION_STANDARD) {
      locationString += "standard";
    } else if (location == KeyEvent.KEY_LOCATION_LEFT) {
      locationString += "left";
    } else if (location == KeyEvent.KEY_LOCATION_RIGHT) {
      locationString += "right";
    } else if (location == KeyEvent.KEY_LOCATION_NUMPAD) {
      locationString += "numpad";
    } else { // (location == KeyEvent.KEY_LOCATION_UNKNOWN)
      locationString += "unknown";
    }

    displayArea.append(keyStatus + newline + "    " + keyString + newline
        + "    " + modString + newline + "    " + actionString + newline
        + "    " + locationString + newline);
    displayArea.setCaretPosition(displayArea.getDocument().getLength());
  }
}








15.21.KeyListener
15.21.1.The KeyListener Interface
15.21.2.The event IDs that the KeyEvent class defines
15.21.3.How to Write a Key Listener
15.21.4.Demonstrates key eventsDemonstrates key events
15.21.5.KeyListener and KeyEvent
15.21.6.Handling Key Presses
15.21.7.Get key pressed as a key character (which is a Unicode character)
15.21.8.Get key pressed as a key code
15.21.9.Setting Focus Traversal Keys in a Component
15.21.10.Listing the Key Bindings in a Component
15.21.11.Make the ENTER key act like the TAB key
15.21.12.Overriding Many Default Typed Key Bindings in a JTextComponent