How to know when a user has really released a key in Java?

Question

(Edited for clarity)

I want to detect when a user presses and releases a key in Java Swing, ignoring the keyboard auto repeat feature. I also would like a pure Java

Answer 1

You might want to use the action map of the component you are interested in. Here's an example that deals with a specific key (SPACE BAR) but I'm sure that if you read the documentation you may be able to modify it to handle generic key presses and releases.

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.beans.PropertyChangeListener;

import javax.swing.Action;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;

public class Main {
    public static void main(String[] args) {
        JFrame f = new JFrame("Test");
        JPanel c = new JPanel();

        c.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
                KeyStroke.getKeyStroke("SPACE"), "pressed");
        c.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
                KeyStroke.getKeyStroke("released SPACE"), "released");
        c.getActionMap().put("pressed", new Action() {
            public void addPropertyChangeListener(
                    PropertyChangeListener listener) {
            }

            public Object getValue(String key) {
                return null;
            }

            public boolean isEnabled() {
                return true;
            }

            public void putValue(String key, Object value) {
            }

            public void removePropertyChangeListener(
                    PropertyChangeListener listener) {
            }

            public void setEnabled(boolean b) {
            }

            public void actionPerformed(ActionEvent e) {
                System.out.println("Pressed space at "+System.nanoTime());
            }
        });
        c.getActionMap().put("released", new Action() {
            public void addPropertyChangeListener(
                    PropertyChangeListener listener) {
            }

            public Object getValue(String key) {
                return null;
            }

            public boolean isEnabled() {
                return true;
            }

            public void putValue(String key, Object value) {
            }

            public void removePropertyChangeListener(
                    PropertyChangeListener listener) {
            }

            public void setEnabled(boolean b) {
            }

            public void actionPerformed(ActionEvent e) {
                System.out.println("Released space at "+System.nanoTime());
            }
        });
        c.setPreferredSize(new Dimension(200,200));


        f.getContentPane().add(c);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.pack();
        f.setVisible(true);
    }
}