Java How to intercept key combinations anywhere on a window using keybindings

Question

My application will be used on a small twin engine aircraft. The environment is "bumpy" and the nipple "mouse" is very hard to use (even in the hanger!). I need to be able to intercept key combinations for at least all the commonly used actions the user wants to take. These would include, for example, alt-C to perform a a calibration, alt-R to start recording data, alt-X to have the app shut down gracefully, etc.

I've only used key Bindings in a demo class and do not understand how use them over an entire window. I have put 5 JPanels containing otherJPpanels and components on my JFrame's ContentPane. All the examples I have found assume some component has focus but pushing TAB 23 times to get to a component is unreasonable.

The app will run under LINUX, probably Ubuntu.

gersonZaragocin · Accepted Answer · 2015-11-25T03:15:09.843

4

In swing you should add a KeyStroke to the main panel's action map: For instance the following code let you refresh the JFrame that contains the JPanel, each time you press [F10] key:

public class MainWindow extends JFrame{
    JPanel central;

    public MainWindow(){
        central = new JPanel();
        // I assume you define your other 5 panels here
        // and add them to the central JPanel.
        getContentPane().add(central, BorderLayout.CENTER);
        registerRefreshAction();
    }

    private void registerRefreshAction(){
        javax.swing.Action refresh = new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                JFrame frame = (JFrame) getTopLevelAncestor();
                frame.setVisible(false);
                frame.getContentPane().repaint();
                frame.setVisible(true);
            }
        };
        KeyStroke keyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_F10, 0);
        central.getActionMap().put("Refresh", refresh);
        central.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(keyStroke, "Refresh");
    }
}

You should call registerRefreshAction in some place in your constructor, as shown before. The other components you mention are included inside the 5 panels and don't need to be shown. It is working in Linux.

edited Nov 25 '15 at 03:15

answered Aug 21 '12 at 21:48

gersonZaragocin

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I edited this for my use but have not succeeded in registering it. it. (I'm new to Swing.) Could you provide an example, please? – Nate Lockwood Aug 22 '12 at 21:35
I edited the source code to show a more realistic sample. Of course if you define the main panel in a different container and add the other 5 panels to it, you can register the KeyStrokes to that Panel's action map. – gersonZaragocin Aug 22 '12 at 22:36
Thank you kindly, it's amazing how obvious some things are when they are pointed out!! AFAIK it works just fine so far. – Nate Lockwood Aug 24 '12 at 00:33
`getContentPane()` has no method `getActionMap()`. Please, explain from where you derived that! – cj5 Sep 19 '14 at 20:50
I missunderstood the returned type of getContentPane(), it is corrected now. Thanks for your observation. – gersonZaragocin Nov 25 '15 at 03:16

score 2 · Answer 2 · answered Aug 21 '12 at 21:40

2

You could try

getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);

or

getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);

I'd probably establish this on a custom content pane

JPanel myContentPane = new JPanel();
frame.setContentPane(myContentPane);

Or use the root pane's input map

If this doesn't work, there is another method, but I'd prefer to see if this works first

answered Aug 21 '12 at 21:40

MadProgrammer

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I sure wish I had known I would have this problem before I set out to design my GUI. All I have is the contentPane with 5 panels on it but lots of buttons and things on those panels. – Nate Lockwood Aug 22 '12 at 21:35

Java How to intercept key combinations anywhere on a window using keybindings

2 Answers2