Following example provides a utility for coalescing multiple high frequency events into a single update event. This can be useful in scenarios where user action generates a series of events (like typing in a field, moving windows etc) and we will like to process a costly operation only at the end of that.

Example

package com.logicbig.uicommon;

import javax.swing.*;

public class CoalescedEventUpdater {
    private Timer timer;

    public CoalescedEventUpdater(int delay, Runnable callback) {
        timer = new Timer(delay, e -> {
            timer.stop();
            callback.run();
        });
    }

    public void update() {
        if (!SwingUtilities.isEventDispatchThread()) {
            SwingUtilities.invokeLater(() -> {timer.restart();});
        } else {
            timer.restart();
        }
    }
}

Example Main

public class CoalesceEventExample {
    public static void main(String[] args) {
        JLabel displayLabel = new JLabel();
        JTextField inputField = new JTextField();
        addTextListener(inputField, displayLabel);
        JFrame frame = createFrame();
        frame.add(inputField, BorderLayout.NORTH);
        frame.add(displayLabel);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private static void addTextListener(JTextField inputField, JLabel displayLabel) {
        CoalescedEventUpdater updater = new CoalescedEventUpdater(400, () -> {
            displayLabel.setText(inputField.getText());
        });
        inputField.getDocument().addDocumentListener(new DocumentListener() {
            @Override
            public void insertUpdate(DocumentEvent e) {
                update();
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                update();
            }

            @Override
            public void changedUpdate(DocumentEvent e) {
                update();
            }

            private void update() {
                updater.update();
            }
        });
    }

    private static JFrame createFrame() {
        JFrame frame = new JFrame("Coalesce Events Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(new Dimension(600, 300));
        return frame;
    }
}

Output

The 'displayLabel' will get updated only after when user has paused for 400ms while typing in the 'inputField'

Example Project

Dependencies and Technologies Used:

• JDK 1.8
• Maven 3.5.4