java - KeyListener not working

Question

public class KL implements KeyListener {

 public static void main(String[] args) {
        final JPopupMenu popup = new JPopupMenu();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);
        frame.setVisible(true);

    }

@Override
public void keyPressed(KeyEvent arg0) {
    System.out.println(arg0.getKeyChar());
}

@Override
public void keyReleased(KeyEvent e) {
    System.out.println(e.getKeyChar());

}

@Override
public void keyTyped(KeyEvent e) {
    System.out.println(e.getKeyChar());

}
}

That's my class, it's probably something really stupid on my part, but my KeyListener here is not working. Nothing comes up on the console.

Answer 1

Let's start with the fact that you're not attached the listener to anything, then move on to the fact that you really should be using Key Bindings

And with example

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestTableEditing {

    public static void main(String[] args) {
        new TestTableEditing();
    }

    public TestTableEditing() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JLabel key;
        private int counter = 0;

        public TestPane() {
            key = new JLabel("...");
            add(key);
            InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
            ActionMap am = getActionMap();
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, 0), "A.pressed");
            am.put("A.pressed", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    System.out.println("A was pressed");
                    key.setText("A was pressed " + (++counter));
                }
            });
        }

    }

}