Java ContextMenu .onActionProperty ()

public final ObjectProperty < EventHandler < ActionEvent >> onActionProperty()

//from w  w  w . j  av a  2s . com
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.ContextMenu;
import javafx.scene.control.Label;
import javafx.scene.control.MenuItem;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import javafx.stage.WindowEvent;

public class Main extends Application {
  public static void main(String[] args) {
    launch(args);
  }
  @Override
  public void start(Stage stage) {
    Scene scene = new Scene(new Group(), 450, 250);
    TextField notification = new TextField();

    MenuItem item1 = new MenuItem("About");
    item1.setOnAction(new EventHandler<ActionEvent>() {
      public void handle(ActionEvent e) {
        System.out.println("About");
      }
    });
    MenuItem item2 = new MenuItem("Preferences");
    item2.setOnAction(new EventHandler<ActionEvent>() {
      public void handle(ActionEvent e) {
        System.out.println("Preferences");
      }
    });
    
    final ContextMenu contextMenu = new ContextMenu(item1, item2);
    contextMenu.setOnShowing(new EventHandler<WindowEvent>() {
      public void handle(WindowEvent e) {
        System.out.println("showing");
      }
    });
    contextMenu.setOnShown(new EventHandler<WindowEvent>() {
      public void handle(WindowEvent e) {
        System.out.println("shown");
      }
    });
    
    System.out.println(contextMenu.onActionProperty());
    
    
    notification.setContextMenu(contextMenu);
    GridPane grid = new GridPane();
    grid.setVgap(4);
    grid.setHgap(10);
    grid.setPadding(new Insets(5, 5, 5, 5));
    grid.add(new Label("To: "), 0, 0);
    grid.add(notification, 1, 0);

    Group root = (Group) scene.getRoot();
    root.getChildren().add(grid);
    stage.setScene(scene);
    stage.show();
  }
}