Methods to debug Java KeyBindings which aren't being captured

Question

As I've added the binding for each JPanel which is in my JFrame, I would have assumed at least one of them to fire when I press the W key. Is my KeyStroke incorrect?

SSCCE:

public class TestTemp extends JFrame {

    public TestTemp() {
        setSize(1000, 800);

        JPanel parentPanel = new JPanel(new MigLayout("", "grow, fill",
                "grow, fill"));
        parentPanel.setBackground(Color.GREEN);
        setContentPane(parentPanel);
        parentPanel.setSize(1000, 800);

        JPanel videoPanel = new JPanel();
        videoPanel.setBackground(Color.CYAN);

        JPanel contentPanel = new JPanel();
        contentPanel.setLayout(new MigLayout("fillx", "[fill]", "[nogrid]"));
        contentPanel.setBackground(Color.YELLOW);

        parentPanel.getInputMap().put(KeyStroke.getKeyStroke("W"), new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("W pressed, parent panel");          
            }                   
        });     

        contentPanel.getInputMap().put(KeyStroke.getKeyStroke("W"), new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("W pressed, content panel");         
            }                   
        });

        videoPanel.getInputMap().put(KeyStroke.getKeyStroke("W"), new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("W pressed, video panel");           
            }                   
        });

        parentPanel.add(videoPanel, "wmin 200");
        parentPanel.add(contentPanel);
    }


    public static void main(String[] args) {
        JFrame frame = new TestTemp();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

Edit: I attempted to give the parentPanel focus using:

parentPanel.setFocusable(true);
parentPanel.requestFocus();

but it appeared not to have any effect.

Edit 2: To ensure it wasn't an incorrect keystroke, I used the keystroke the docs give in their example:

KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0)

but again, hitting Enter had no effect.

score 0 · Accepted Answer · edited May 23 '17 at 12:27

Try this:

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import net.miginfocom.swing.MigLayout;

public class T extends JFrame {

    public T() {
        setSize(1000, 800);

        JPanel parentPanel = new JPanel(new MigLayout("", "grow, fill",
                "grow, fill"));
        parentPanel.setBackground(Color.GREEN);
        getContentPane().add(parentPanel);
        parentPanel.setSize(1000, 800);

        JPanel videoPanel = new JPanel();
        videoPanel.setBackground(Color.CYAN);

        JPanel contentPanel = new JPanel();
        contentPanel.setLayout(new MigLayout("fillx", "[fill]", "[nogrid]"));
        contentPanel.setBackground(Color.YELLOW);

        parentPanel.getActionMap().put("enter", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("Enter pressed, parent panel");
            }
        });

        InputMap inputMap = parentPanel.getInputMap();
        inputMap.put( KeyStroke.getKeyStroke(KeyEvent.VK_ENTER,0), "enter");

        parentPanel.add(videoPanel, "wmin 200");
        parentPanel.add(contentPanel);
    }


    public static void main(String[] args) {
        JFrame frame = new T();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

I don't think MigLayout is the issue.

Use getActionMap instead of getInputMap to wait for action events.
Separate the InputMap to listen for keystrokes.

The enter keyboard events are now written to standard output.

See these links for details:

Generally speaking, when you encounter a difficult problem, try to make the simplest case work. Once you have the simplest case working (e.g., one panel accepting keyboard inputs), then build on the complexity. You could have even removed MigLayout, for example, to see if it was affecting the keyboard inputs.

Methods to debug Java KeyBindings which aren't being captured

1 Answers1