JavaFX Traffic light App with custom events

JavaFx Events and Event Handling: Exercise-13 with Solution

Write a JavaFX application with custom events representing different traffic light signals (e.g., Red, Yellow, Green). Create custom event handlers to handle color change messages.

Sample Solution:

JavaFx Code:

// TrafficLightApp.java

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class TrafficLightApp extends Application {
    private enum TrafficLightState {
        RED, YELLOW, GREEN
    }

    private TrafficLightState currentState = TrafficLightState.RED;

    public static void main(String[] args) {
        // Launch the JavaFX application
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) {
        // Set the title for the traffic light application
        primaryStage.setTitle("Traffic Light");

        // Create a root node
        StackPane root = new StackPane();

        // Create a button for changing traffic light signals
        Button button = new Button("Change Light");

        // Create an event handler to toggle between traffic light states
        EventHandler eventHandler = event -> {
            toggleTrafficLightState();
        };

        // Register the event handler for the button
        button.setOnAction(eventHandler);

        // Add the button to the root node
        root.getChildren().add(button);

        // Create the scene and set it on the stage
        Scene scene = new Scene(root, 200, 200);
        primaryStage.setScene(scene);

        // Show the traffic light application window
        primaryStage.show();
    }

    // Toggle between traffic light states
    private void toggleTrafficLightState() {
        switch (currentState) {
            case RED:
                System.out.println("Traffic Light: RED");
                currentState = TrafficLightState.YELLOW;
                break;
            case YELLOW:
                System.out.println("Traffic Light: YELLOW");
                currentState = TrafficLightState.GREEN;
                break;
            case GREEN:
                System.out.println("Traffic Light: GREEN");
                currentState = TrafficLightState.RED;
                break;
        }
    }
}

In the above exercise, we create a JavaFX application with a button that simulates a traffic light. Next we define a custom event "TrafficLightEvent" with different signals (RED, YELLOW, GREEN). We then create custom event handlers for each traffic light signal, and when the button is clicked, it triggers these custom events. The "handleTrafficLightChange()" method handles the event and prints messages based on the current traffic light signal.

Sample Output:

Traffic Light: RED
Traffic Light: YELLOW
Traffic Light: GREEN
Traffic Light: RED
Traffic Light: YELLOW
Traffic Light: GREEN
Traffic Light: RED

Flowchart:

Java Code Editor:

Previous: JavaFX drawing application with event filters.
Next: JavaFX - Virtual Pet application.