How to define the keyStroke for the numpad - enter key

Question

I'm about to use keybinding in a swing application for the num pad enter key, but the key is difficult to catch. All examples I have seen rely on something like
key == KeyEvent.VK_KP_LEFT

where VK_KP_LEFT is some predefined value. Other options are to define a keystoke like this:
KeyStroke.getKeyStroke("control A");
KeyStroke.getKeyStroke(KeyEvent.VK_A, InputEvent.CTRL_MASK);

but I have not found the "modifier" for numpad.

What is easily to obtain is the difference between the general and the numpad-enter: All numpad-keys (indepently if switched in the numeric mode or not) get assigned the
getKeyLocation() == 4
(I spottetd this from key pressed / key released methods)

The question is:
How to properly prepare the keyStroke for numpad enter key to use it in the
inputMap.put(KeyStroke keyStroke, Object actionMapKey)
key binding method?

Thanks,
Tarik

tenorsax · Answer 1 · 2013-04-17T22:24:05.010

If you're looking for binding Enter key you can use KeyEvent.VK_ENTER, ie:

getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0), "someAction");
getActionMap().put("someAction", someAction);

Here is a short example:

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

public class Test {
    public static void main(String[] args) throws Exception {
        final JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel();
        panel.add(new JLabel("Hit Enter"));

        Action someAction = new AbstractAction() {
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(frame, "Got it");
            }
        };

        panel.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
                KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0), "someAction");
        panel.getActionMap().put("someAction", someAction);

        frame.add(panel);

        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

EDIT: VK_ENTER on numeric pad vs main keyboard

After some testing, it looks like it may not be possible to bind these keys separately. The same KeyStroke is generated for both keys. The implementation of JComponent.processKeyBinding does not examine the KeyEvent, all it cares is KeyStroke in order to find the desired action.

SwingUtilities.notifyAction that is responsible for dispatching the actual action does not delegate all the details of the KeyEvent (only key, modifiers and when). So inside action there is no way to distinguish either as there is no details in ActionEvent.

If it worth the trouble, you can override processKeyBinding and add some logic if needed. You can also use KeyboardFocusManageraddKeyEventDispatcher() for blocking one of the keys.

While technically correct, in that it should respond to both enter keys, I believe the OP wants to restrict the Action just to the keypad enter key — MadProgrammer, Apr 17 '13 at 20:58
@MadProgrammer True, I may have misinterpreted the question. It may not be possible to distinguish between the two keys. I wonder if OP can provide more details. — tenorsax, Apr 17 '13 at 22:19

score -1 · Answer 2 · answered Apr 17 '13 at 20:40

-1

How about this?

if(keyEvent.getKeyLocation() == KeyEvent.KEY_LOCATION_NUMPAD 
&& keyEvent.getKeyCode() == KeyEvent.VK_ENTER)

answered Apr 17 '13 at 20:40

Hugo Rocha

537
5
23

5

With respect, this isn't question is about Key Listeners, its about Key bindings, its not going to be possible ascertain the location of the KeyEvent when the key is activated – MadProgrammer Apr 17 '13 at 20:57
1

Thanks for your help. Seems, it is difficult to bind exactly to the numpad_enter only. At the moment, I'm not sure if it is worth the trouble to go for the expensive solutions or change design to key listener. At the end, the code should match the requirements and shouldn't look more difficult than needed :-) . Cheers, Tarik – tarik Apr 19 '13 at 19:07

How to define the keyStroke for the numpad - enter key

2 Answers2