adding KeyListener to JPanel !!!!

[sanu]

hi....

In my program, i want to add mouse and key listeners to a JPanel. there is no problem with the mouse listener. But the keylistener is not working. my code looks like

myPanel.addMouseListener(this);
myPanel.addKeyListener(this);

my class implements these two listeners. the program compiles and it is running. i am not able to debug the error with keylistener. it seems key listener has not added to the JPanel. somebody pls help...

thanx...

sanu

[sjalle]

I think you have to use the panel requestFocus() method to capture keyStrokes.
Note, the KeyTyped event is partially deaf...
Go for the KeyPressed event.

[sanu]

ya....its working...
i modified it to
jpanel.setFocusable(true);
jpanel.addKeyListener(this);
now it works. But there still remains a problem. the listener tracks all keys except the TAB key. when TAB key is pressed neither keyPressed nor keyReleased is calling. wat could be the problem....

sanu

[sjalle]

I have tried with key binding also, but it responds to all the
KeyEvent.VK_<key> but not to KeyEvent.VK_TAB.
It would be nice if anyone could tell us...

Her is the keylistener and keybinding setup (that fails), you may want to
mess with it...

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;


/**
 * Listen to keys typed
 */

public class KeyListenerFrame extends JFrame implements KeyListener {
  GridLayout gridLayout1 = new GridLayout();
  JPanel listenerPan = new JPanel();

  public KeyListenerFrame() {
    try {
      jbInit();
      listenerPan.addKeyListener(this);
      addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
          System.exit(0);
        }
      });      
      listenerPan.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_PAGE_UP,0,true),
                             "showKey");
      listenerPan.getActionMap().put("showKey",
                              showKey);

    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }
  public static void main(String[] args) {
    KeyListenerFrame klf = new KeyListenerFrame();
    klf.setBounds(10,10,200,200);
    klf.setVisible(true);
    klf.focusPanel();
  }
  public void focusPanel() {
     listenerPan.requestFocus();
  }
  private void jbInit() throws Exception {
    this.getContentPane().setLayout(gridLayout1);
    this.getContentPane().add(listenerPan, null);
  }
  Action showKey = new AbstractAction() {
    public void actionPerformed(ActionEvent e) {
        System.out.println("VK_PAGE_UP");
    }
  };


  public void keyTyped(KeyEvent e) {
    System.out.println(e.toString());
  }
  public void keyPressed(KeyEvent e) {
   System.out.println(e.toString());
  }
  public void keyReleased(KeyEvent e) {
    System.out.println(e.toString());
  }
}

PS: this php setup likes to put spaces in the code....

[sanu]

hi...

once the tab key is pressed, keyListener seems to have stopped functioning. i am not able to track a single key after that. is it becoz the component (jpanel) loses its focus when we press the tab key. if so wat should be done...pls help

sanu

[sjalle]

.. I think, but this solution may have some side effects. I have overridden
the getFocusTraversalKeys method in Component and put this in
a JFrame exension. (I think) this implementation stops all key entries
that defines a forward/backward forcus traversal from actuall doing
a traversal. Anyway, the TAB key comes through loud and clear, both tab
and shift+tab

HashSet emptySet=new HashSet();
.
.
public Set getFocusTraversalKeys (int id) {
  if (id==KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS ||
      id==KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS) {
    return emptySet;
  } else return super.getFocusTraversalKeys(id);
}

[dugo]

I know this may be too late a response, but I think you will have to release Tab and SHift+Tab from their default traversal roles by doing

JComponent.setFocusTraversalKeysEnabled(false);