CheckBox

A CheckBox is a UI element that lets the user choose YES or NO.

Examples:

✅ Accept terms ⬜ Subscribe to newsletter

👉 It has only two states:

• Checked → true
• Unchecked → false

1️⃣ FXML: Define a CheckBox

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.CheckBox?>
<?import javafx.scene.layout.VBox?>

<VBox spacing="20" alignment="CENTER" xmlns="http://javafx.com/javafx/17"
      xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.example.CheckBoxController">

    <CheckBox text="Accept Terms" fx:id="termsCheckBox" onAction="#handleCheckBoxAction"/>
    
</VBox>

Explanation:

• fx:id="termsCheckBox" → lets the controller access this checkbox.
• onAction="#handleCheckBoxAction" → calls the method in the controller when the checkbox is clicked (checked or unchecked).

2️⃣ Controller: Handle the CheckBox

package com.example;

import javafx.fxml.FXML;
import javafx.scene.control.Alert;
import javafx.scene.control.CheckBox;

public class CheckBoxController {

    @FXML
    private CheckBox termsCheckBox;

    @FXML
    private void handleCheckBoxAction() {
        if (termsCheckBox.isSelected()) {
            Alert alert = new Alert(Alert.AlertType.INFORMATION);
            alert.setTitle("CheckBox Selected");
            alert.setHeaderText(null);
            alert.setContentText("You accepted the terms.");
            alert.showAndWait();
        } else {
            Alert alert = new Alert(Alert.AlertType.WARNING);
            alert.setTitle("CheckBox Unselected");
            alert.setHeaderText(null);
            alert.setContentText("You did not accept the terms.");
            alert.showAndWait();
        }
    }
}

Explanation:

• termsCheckBox.isSelected() → checks if the checkbox is checked.
• We show an Alert depending on whether it’s checked or not.

3️⃣ Main Class: Load the FXML

package com.example;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class MainApp extends Application {

    @Override
    public void start(Stage stage) throws Exception {
        FXMLLoader loader = new FXMLLoader(getClass().getResource("checkbox_layout.fxml"));
        Scene scene = new Scene(loader.load(), 300, 200);
        stage.setScene(scene);
        stage.setTitle("CheckBox Example");
        stage.show();
    }

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

✅ Key Notes:

1. Use isSelected() to check the state of a CheckBox.
2. Use setSelected(true/false) if you want to change the state programmatically.
3. onAction fires every time the user clicks the checkbox, whether checking or unchecking.