ChoiceBox and labels in JavaFX

Last update on May 08 2025 12:50:54 (UTC/GMT +8 hours)

Write a JavaFX application that creates a ChoiceBox with a list of colors. Display a label that changes its text based on the selected color from the ChoiceBox.

Sample Solution:

JavaFx Code:

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.scene.Scene;
import javafx.scene.control.ChoiceBox;
import javafx.scene.control.Label;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class Main extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) {
        // Create a label to display the selected color.
        Label colorLabel = new Label("Selected Color: ");

        // Create a ChoiceBox with a list of colors.
        ChoiceBox colorChoiceBox = new ChoiceBox<>(
                FXCollections.observableArrayList(
                        "Red", "Green", "Blue", "Yellow", "Orange", "Purple"
                )
        );

        // Set an action for the ChoiceBox.
        colorChoiceBox.setOnAction(event -> {
            String selectedColor = colorChoiceBox.getValue();
            colorLabel.setText("Selected Color: " + selectedColor);
        });

        // Create a layout for the ChoiceBox and label.
        VBox root = new VBox(10); // 10 is the spacing between elements.
        root.getChildren().addAll(colorChoiceBox, colorLabel);

        // Create the scene and set it in the stage.
        Scene scene = new Scene(root, 300, 200); // Width and height of the window.
        primaryStage.setScene(scene);

        // Set the title of the window.
        primaryStage.setTitle("Color Choice App");

        // Show the window.
        primaryStage.show();
    }
}

Explanation:

In the exercise above -

Import the necessary JavaFX libraries.
Create a class "Main" that extends "Application" and overrides the "start()" method.
Inside the "start()" method:

Create a label with the initial text "Selected Color:."

Create a ChoiceBox that contains a list of colors (Red, Green, Blue, Yellow, Orange, Purple). The "FXCollections.observableArrayList()" method is used to populate the ChoiceBox.
Set an action for the ChoiceBox:

When a color is selected, it updates the label's text to show the selected color.

Organize the ChoiceBox and label in a vertical layout (VBox) with 10 pixels of spacing between them.
Create a Scene with the layout, setting the window dimensions to 300x200.
Set the window's title to "Color Choice App."
Show the window.