JavaFX 17. Properties

1. Main.java

package application;
    
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.stage.Stage;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
 
 
public class Main extends Application {
    @Override
    public void start(Stage primaryStage) {
        try {
            Parent root = new FXMLLoader().load(getClass().getResource("/application/Main.fxml"));
            Scene scene = new Scene(root,400,400);
            scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
            primaryStage.setScene(scene);
            primaryStage.show();
        } catch(Exception e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        launch(args);
    }
}
 

2. Main.fxml

<?xml version="1.0" encoding="UTF-8"?>
 
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.AnchorPane?>
 
 
<AnchorPane prefHeight="300.0" prefWidth="300.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8.0.60" fx:controller="application.MainController">
   <children>
      <Button layoutX="116.0" layoutY="209.0" mnemonicParsing="false" onAction="#BtnClick" text="Button" />
      <Label fx:id="lblStatus" layoutX="90.0" layoutY="57.0" prefHeight="62.0" prefWidth="121.0" text="Label" />
   </children>
</AnchorPane>
 

3. MyNumber.java

package application;
 
import javafx.beans.property.*;
 
public class MyNumber {
    
    private DoubleProperty number;
 
    public double getNumber() {
        if(number != null){
            return number.get();
        }else{
            return 0;
        }
        
    }
 
    public void setNumber(double number) {
        this.numberProperty().set(number); 
    }
    
    public final DoubleProperty numberProperty(){
        if(number == null){
            number = new SimpleDoubleProperty(0);
        }
        return number;
    }
    
}
 

4. MainController.java

package application;
 
import java.net.URL;
import java.util.ResourceBundle;
 
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
 
public class MainController implements Initializable {
 
    final MyNumber myNum = new MyNumber();
    
    @FXML
    private Label lblStatus;
    
    @Override
    public void initialize(URL location, ResourceBundle resources) {
        myNum.setNumber(0);
        myNum.numberProperty().addListener(new ChangeListener<Object>() {
 
            @Override
            public void changed(ObservableValue<? extends Object> observable, Object oldValue, Object newValue) {
                lblStatus.setText(new Double(myNum.getNumber()).toString());
                
            }
        });
        
    }
 
    public void BtnClick(ActionEvent event) {
        myNum.setNumber(myNum.getNumber() + 1);
    }
}
 

properties 는 속성, 성질 등을 뜻한다. JavaFX에서 properties 는 '속성 감시' 라는 표현으로 사용된다. 내가 이해한 바로는 속성 값이 변화하면 즉각적으로 변화된 값을 사용할 수 있도록 해주는 기능이다. 구체적으로 속성값에 변화가 발생하면, changelistener 의 changed() 메소드를 호출하여 그 변화된 속성값을 사용할 수 있도록 해주는 것이다.