NotificationApp.java

import java.awt.*;
import java.awt.event.ActionListener;
import java.io.IOException;

import javax.swing.SwingUtilities;

/**
 * A simple application to display a desktop notification using Java's SystemTray.
 */
public class NotificationApp {

    // --- Configuration for the Notification ---
    private static final String NOTIFICATION_TITLE = "Crowd Alert!";
    private static final String NOTIFICATION_MESSAGE = "Someone in your area has tested positive for COVID-19. Tap for more information.";
    private static final TrayIcon.MessageType MESSAGE_TYPE = TrayIcon.MessageType.WARNING;
    
    // NOTE: This path should point to a small image (e.g., 16x16 or 32x32) 
    // for the tray icon. The image must be available when running the program.
    private static final String ICON_PATH = "default_icon.png"; 

    public static void main(String[] args) {
        // Ensure the code runs on the Event Dispatch Thread (EDT) for GUI operations
        SwingUtilities.invokeLater(NotificationApp::runNotification);
    }

    /**
     * Initializes the SystemTray and displays the notification.
     */
    private static void runNotification() {
        // Step 7: Handle errors during setup
        if (!SystemTray.isSupported()) {
            System.err.println("System Tray is not supported on this platform.");
            return;
        }

        try {
            // Step 2 & 4: Design/Set the notification icon
            // We need a dummy icon to represent the application in the system tray
            // The image file must be present in the project folder!
            Image icon = Toolkit.getDefaultToolkit().getImage(ICON_PATH);
            
            // Step 2: Create a TrayIcon
            TrayIcon trayIcon = new TrayIcon(icon, "COVID-19 Notifier");
            trayIcon.setImageAutoSize(true); 

            // Step 3: Get the SystemTray instance and add the icon
            final SystemTray tray = SystemTray.getSystemTray();
            tray.add(trayIcon);

            // Step 5: Allow user interaction (Click listener)
            // This is what happens when the user clicks the notification pop-up.
            ActionListener clickListener = e -> {
                System.out.println("Notification clicked! Opening web page...");
                // Step 5: Example of user action - opening a URL
                try {
                    // Open a URL in the default browser (for more info)
                    Desktop.getDesktop().browse(java.net.URI.create("https://www.who.int/emergencies/diseases/novel-coronavirus-2019"));
                } catch (IOException ex) {
                    System.err.println("Could not open browser: " + ex.getMessage());
                }
            };
            trayIcon.addActionListener(clickListener);
            
            // Step 4 & 3: Display the notification (Balloon Tip)
            // The notification appearance is OS-dependent.
            trayIcon.displayMessage(
                NOTIFICATION_TITLE, 
                NOTIFICATION_MESSAGE, 
                MESSAGE_TYPE
            );

            // Optional: Remove the icon after a delay (e.g., 10 seconds)
            // The notification will disappear automatically after a few seconds based on OS settings.
            // We keep the icon visible for 10 seconds for user to interact with the tray.
            new java.util.Timer().schedule(
                new java.util.TimerTask() {
                    @Override
                    public void run() {
                        tray.remove(trayIcon);
                        System.exit(0); // Exit the application
                    }
                }, 
                10000 // 10 seconds
            );

        } catch (AWTException | IllegalArgumentException e) {
            // Step 7: Handle potential exceptions
            System.err.println("Error setting up System Tray or Icon: " + e.getMessage());
        }
    }
}