检测已取消拖动的JavaFX

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.input.*;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class DragDetectionExample extends Application {

    @Override
    public void start(Stage primaryStage) {
        Label label = new Label("Drag me!");

        label.setOnDragDetected(new EventHandler<MouseEvent>() {
            public void handle(MouseEvent event) {
                Dragboard db = label.startDragAndDrop(TransferMode.ANY);
                ClipboardContent content = new ClipboardContent();
                content.putString(label.getText());
                db.setContent(content);
                event.consume();
            }
        });

        label.setOnDragDone(new EventHandler<DragEvent>() {
            public void handle(DragEvent event) {
                if (event.isDropCompleted()) {
                    System.out.println("Drag canceled");
                }
                event.consume();
            }
        });

        StackPane root = new StackPane();
        root.getChildren().add(label);

        Scene scene = new Scene(root, 200, 200);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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