How to emulate pressing media keys in Java?

Question

How can I emulate pressing media keys in Java? Such as play/pause, next/previous, volume control.

C# has VK_MEDIA_PLAY_PAUSE, VK_MEDIA_NEXT_TRACK

Answer 1

I improved Alex's KeySpy application. The JFrame holds the focus so you can minimize or maximize the application, and still press any key when the application is in focus.

Here's the GUI.

I put the information in a label / value grid to make it easier to find the value(s) that you're interested in.

And here's the code. This is a good example of a GridBagLayout.

package com.ggl.testing;

import java.awt.Component;
import java.awt.Container;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class KeySpy implements Runnable {

    private KeySpyPanel keySpyPanel;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new KeySpy());
    }

    @Override
    public void run() {
        final JFrame frame = new JFrame("Key Spy");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationByPlatform(true);
        frame.addWindowFocusListener(new WindowAdapter() {
            public void windowGainedFocus(WindowEvent e) {
                frame.requestFocusInWindow();
            }
        });

        keySpyPanel = new KeySpyPanel();
        frame.add(keySpyPanel.getPanel());
        frame.addKeyListener(new KeyPressedListener(this));

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

    public KeySpyPanel getKeySpyPanel() {
        return keySpyPanel;
    }

    public class KeySpyPanel {

        private final Insets bottomInsets = new Insets(10, 10, 10, 10);
        private final Insets normalInsets = new Insets(10, 10, 0, 10);

        private JPanel panel;

        private JTextField keyCodeField;
        private JTextField keyTextField;
        private JTextField keyCharField;
        private JTextField keyLocationField;
        private JTextField modifiersField;
        private JTextField extModifiersField;
        private JTextField rawCodeField;
        private JTextField primaryLevelUnicodeField;
        private JTextField scancodeField;
        private JTextField extendedKeyCodeField;

        public KeySpyPanel() {
            createPartControl();
        }

        private void createPartControl() {
            panel = new JPanel();
            panel.setLayout(new GridBagLayout());

            int gridy = 0;

            JLabel anyKeyLabel = new JLabel("Press any key");
            anyKeyLabel.setFont(anyKeyLabel.getFont().deriveFont(36F));
            anyKeyLabel.setHorizontalAlignment(JLabel.CENTER);
            addComponent(panel, anyKeyLabel, 0, gridy++, 2, 1, normalInsets,
                    GridBagConstraints.CENTER, GridBagConstraints.HORIZONTAL);

            JLabel keyCodeLabel = new JLabel("KeyCode:");
            addComponent(panel, keyCodeLabel, 0, gridy, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            keyCodeField = new JTextField(20);
            keyCodeField.setEditable(false);
            addComponent(panel, keyCodeField, 1, gridy++, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            JLabel keyTextLabel = new JLabel("KeyText:");
            addComponent(panel, keyTextLabel, 0, gridy, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            keyTextField = new JTextField(20);
            keyTextField.setEditable(false);
            addComponent(panel, keyTextField, 1, gridy++, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            JLabel keyCharLabel = new JLabel("KeyChar:");
            addComponent(panel, keyCharLabel, 0, gridy, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            keyCharField = new JTextField(20);
            keyCharField.setEditable(false);
            addComponent(panel, keyCharField, 1, gridy++, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            JLabel keyLocationLabel = new JLabel("KeyLocation:");
            addComponent(panel, keyLocationLabel, 0, gridy, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            keyLocationField = new JTextField(20);
            keyLocationField.setEditable(false);
            addComponent(panel, keyLocationField, 1, gridy++, 1, 1,
                    normalInsets, GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            JLabel modifiersLabel = new JLabel("Modifiers:");
            addComponent(panel, modifiersLabel, 0, gridy, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            modifiersField = new JTextField(20);
            modifiersField.setEditable(false);
            addComponent(panel, modifiersField, 1, gridy++, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            JLabel extModifiersLabel = new JLabel("ExtModifiers:");
            addComponent(panel, extModifiersLabel, 0, gridy, 1, 1,
                    normalInsets, GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            extModifiersField = new JTextField(20);
            extModifiersField.setEditable(false);
            addComponent(panel, extModifiersField, 1, gridy++, 1, 1,
                    normalInsets, GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            JLabel rawCodeLabel = new JLabel("RawCode:");
            addComponent(panel, rawCodeLabel, 0, gridy, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            rawCodeField = new JTextField(20);
            rawCodeField.setEditable(false);
            addComponent(panel, rawCodeField, 1, gridy++, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            JLabel primaryLevelUnicodeLabel = new JLabel("PrimaryLevelUnicode:");
            addComponent(panel, primaryLevelUnicodeLabel, 0, gridy, 1, 1,
                    normalInsets, GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            primaryLevelUnicodeField = new JTextField(20);
            primaryLevelUnicodeField.setEditable(false);
            addComponent(panel, primaryLevelUnicodeField, 1, gridy++, 1, 1,
                    normalInsets, GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            JLabel scancodeLabel = new JLabel("Scancode:");
            addComponent(panel, scancodeLabel, 0, gridy, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            scancodeField = new JTextField(20);
            scancodeField.setEditable(false);
            addComponent(panel, scancodeField, 1, gridy++, 1, 1, normalInsets,
                    GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            JLabel extendedKeyCodeLabel = new JLabel("ExtendedKeyCode:");
            addComponent(panel, extendedKeyCodeLabel, 0, gridy, 1, 1,
                    bottomInsets, GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);

            extendedKeyCodeField = new JTextField(20);
            extendedKeyCodeField.setEditable(false);
            addComponent(panel, extendedKeyCodeField, 1, gridy++, 1, 1,
                    bottomInsets, GridBagConstraints.LINE_START,
                    GridBagConstraints.HORIZONTAL);
        }

        private void addComponent(Container container, Component component,
                int gridx, int gridy, int gridwidth, int gridheight,
                Insets insets, int anchor, int fill) {
            GridBagConstraints gbc = new GridBagConstraints(gridx, gridy,
                    gridwidth, gridheight, 1.0D, 1.0D, anchor, fill, insets, 0,
                    0);
            container.add(component, gbc);
        }

        public JPanel getPanel() {
            return panel;
        }

        public void setKeyPressed(KeyEvent event) {
            String s = event.toString();

            keyCodeField.setText(getValue("keyCode", s));
            keyTextField.setText(getValue("keyText", s));
            keyCharField.setText(getValue("keyChar", s));
            keyLocationField.setText(getValue("keyLocation", s));
            modifiersField.setText(getValue("modifiers", s));
            extModifiersField.setText(getValue("extModifiers", s));
            rawCodeField.setText(getValue("rawCode", s));
            primaryLevelUnicodeField
                    .setText(getValue("primaryLevelUnicode", s));
            scancodeField.setText(getValue("scancode", s));
            extendedKeyCodeField.setText(getValue("extendedKeyCode", s));
        }

        private String getValue(String key, String line) {
            int sPos = line.indexOf(key);
            if (sPos >= 0) {
                int nPos = sPos + key.length() + 1;
                int ePos = line.indexOf(",", nPos);
                if (ePos < 0) {
                    ePos = line.indexOf("]", nPos);
                }
                if (ePos >= 0) {
                    return line.substring(nPos, ePos);
                }
            }

            return "";
        }

    }

    public class KeyPressedListener extends KeyAdapter {

        private KeySpy keySpyFrame;

        public KeyPressedListener(KeySpy keySpyFrame) {
            this.keySpyFrame = keySpyFrame;
        }

        @Override
        public void keyPressed(KeyEvent event) {
            keySpyFrame.getKeySpyPanel().setKeyPressed(event);
        }
    }

}