Where to addKeyListener in order to 'always' be listening

Question

I need a keylistener to be always 'listening' for the escape key to be pressed, to then exit the program.

I have tried typing addKeyListener(this); in my main constructor (the one with the panel being drawn in) and have used

public void keyPressed( KeyEvent e)

{
      int code = e.getKeyCode();
      if(code == KeyEvent.VK_ESCAPE)
      {
           System.exit( 0 );
      }


}

I get no errors, but pressing the escape key doesn't seem to do anything, any suggestions?

Possible duplicate of http://stackoverflow.com/questions/286727/java-keylistener-for-jframe-is-being-unresponsive — Ravindra Gullapalli, Mar 12 '13 at 12:45
Don't use KeyListener, but rather use KeyBindings. This will avoid the kind of issues you are describing. — Guillaume Polet, Mar 12 '13 at 13:08

score 2 · Accepted Answer · answered Mar 12 '13 at 12:44

2

Top-Level Container by default never receiving KeyEvent from KeyListener, by default, but is possible with a few code lines, wrong idea, wrong listener
JPanel by defaul react to KeyEvent, but only in the case that isFocusable, is FocusOwner, wrong idea, wrong listener, (for example) because you needed to move Focus from JTextField to JPanel programatically, wrong idea
add KeyBindings to JFrame/ JDialog / JWindow, accesible by default for Swing JComponent, not for AWT Components

answered Mar 12 '13 at 12:44

mKorbel

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Thanks for your help, I set the focus to the panel using requestFocusInWindow(); and assigned the keylistner to the panel directly – Mikeymca Mar 12 '13 at 13:05
hmmmm see clear, simple, [but great workaround Escape Key and Dialog](http://tips4java.wordpress.com/2010/10/17/escape-key-and-dialog/) by @camickr – mKorbel Mar 12 '13 at 13:35

score 1 · Answer 2 · answered Mar 12 '13 at 13:15

You can use the InputMap/ActionMap mechanism :

    Object escapeActionKey = new Object();
    pnl.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke("ESCAPE"), escapeActionKey);
    pnl.getActionMap().put(escapeActionKey, new AbstractAction() {
        public void actionPerformed(ActionEvent e) {
            System.err.println("escape 1");
        }
    });

JComponent.WHEN_IN_FOCUSED_WINDOW means that this keystroke is available when the pnl component is in the focused window.

Or you can also add a global AWTEventListener listener :

    Toolkit.getDefaultToolkit().addAWTEventListener(new AWTEventListener() {
        public void eventDispatched(AWTEvent event) {
            if(event.getID() == KeyEvent.KEY_PRESSED) {
                KeyEvent kEvent = (KeyEvent) event;
                boolean isEsc = (kEvent.getKeyCode() == KeyEvent.VK_ESCAPE);
                if(isEsc) {
                    System.err.println("escape 2");
                }
            }
        }
    }, AWTEvent.KEY_EVENT_MASK);

score 0 · Answer 3 · answered Mar 12 '13 at 12:45

0

In Swing there is a top layer panel : the GlassPane which allow to handle event at top level (to avoid other widget to comsume the event)

answered Mar 12 '13 at 12:45

Gab

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How could I add a listener to the GlassPane? I'm getting 'cannot find symbol' – Mikeymca Mar 12 '13 at 12:49
This has the capacity to consume all the events, meaning none of the other components can react to them – MadProgrammer Mar 12 '13 at 21:20

Where to addKeyListener in order to 'always' be listening

3 Answers3