Keylistener on jpanel won't work

Question

I'm trying to add a keylistener to my JPanel but it won't work even after this:

put.setFocusable(true);
    put.requestFocusInWindow();
    KeyboardHandler keyhandler=new KeyboardHandler();
    put.addKeyListener(keyhandler);
}
private class KeyboardHandler implements KeyListener{
    public void keyPressed(KeyEvent e) {
    System.out.println("OVDE ZZZ");
    if(e.getKeyCode()==17) ctrl=true;
        if(e.getKeyCode()==90) z=true;
        if(ctrl && z){
            if (UndoBrojac==0) JOptionPane.showMessageDialog(null, "You can't undo that");
            else{
                UndoBrojac--;
                put.setUndo(UndoBrojac);
            }
        }

}

public void keyReleased(KeyEvent e){
    if (e.getKeyCode()==17) ctrl = false;
    if (e.getKeyCode()==90) z = false;
}

    public void keyTyped(KeyEvent e) {}
}

I'm trying to add ctrl+z but it doesn't work.

You should use `KeyEvent.VK_CONTROL` and `KeyEvent.VK_Z` to avoid magic constants. — Dahaka, Jul 11 '13 at 10:39
For Swing, typically use key bindings over the AWT based, lower level, `KeyListener`. See [How to Use Key Bindings](http://docs.oracle.com/javase/tutorial/uiswing/misc/keybinding.html) for details on how to use them. — Andrew Thompson, Jul 11 '13 at 10:56
Why would it work ? It requires the component to have focus, and I guess in your terms the top-level container is getting the focus, so use KeyBinding as already suggested :-) This post regarding [Motion using Keyboard](http://tips4java.wordpress.com/2013/06/09/motion-using-the-keyboard/), by @camickr will definitely interest you :-) — nIcE cOw, Jul 11 '13 at 11:06
I found that focus must be done after being set to visible, so creating a new class now — Nemanja Neca Stojanovic, Jul 11 '13 at 11:09
what happened when you typed _swing keylistener not working_ into the search field in the upper trailing edge of this or any other page of the site? — kleopatra, Jul 11 '13 at 11:12
well, that's probably because you didn't follow the answers ;-) The one I choose as the duplicate (in voting to close) mentions both the focus issue and that you should _not_ use a keyListener - so why didn't you learn from that, update your approach accordingly and then come back? — kleopatra, Jul 11 '13 at 11:16
See also [*Implementing Undo and Redo*](http://docs.oracle.com/javase/tutorial/uiswing/components/generaltext.html#undo). — trashgod, Jul 11 '13 at 13:30

score 2 · Answer 1 · edited May 23 '17 at 12:11

2

Several helpful comments suggest using Key Bindings. As shown here, it is particularly easy to specify KeyEvent.VK_Z as an ACCELERATOR_KEY in the context of an Action. If you are undoing changes to a text component, see How to Write an Undoable Edit Listener; the TextComponentDemo cited there illustrates a typical UndoAction.

edited May 23 '17 at 12:11

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answered Jul 11 '13 at 13:43

trashgod

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Keylistener on jpanel won't work

1 Answers1