JavaFX将TreeTableColumn拖放到另一个节点

Question

出于教育目的，我尝试将TreeTableColumn拖到TreeTableView之外的节点上并接受drop。可能的用例是分组或多级排序。

我在onDragDetected上搜索TreeTableColumn，但是此方法不存在。 （TreeTableColumn的图形默认为null） TreeTableView确实提供了这种方法，但是当我开始拖动列时我没有任何事件。

所以我的尝试是将Label作为图形放到TreeTableColumn上。 这使我可以将Column拖到Table之外。但这以掉落后的图形故障结束。

关于如何解决此故障或完全摆脱“ TreeTableColumn”中的“ Graphics”包装的任何想法？

这是一个显示我的问题的示例应用程序

public class TreeTableViewSample extends Application {

    List<Employee> employees = Arrays.<Employee>asList(new Employee("Ethan Williams", "ethan.williams@example.com"),
            new Employee("Emma Jones", "emma.jones@example.com"),
            new Employee("Michael Brown", "michael.brown@example.com"),
            new Employee("Anna Black", "anna.black@example.com"), new Employee("Rodger York", "roger.york@example.com"),
            new Employee("Susan Collins", "susan.collins@example.com"));

    final TreeItem<Employee> root = new TreeItem<>(new Employee("Sales Department", ""));

    public static void main(String[] args) {
        Application.launch(TreeTableViewSample.class, args);
    }

    @Override
    public void start(Stage stage) {
        root.setExpanded(true);
        employees.stream().forEach((employee) -> {
            root.getChildren().add(new TreeItem<>(employee));
        });
        stage.setTitle("Tree Table View Sample with DND");
        final Scene scene = new Scene(new BorderPane(), 400, 400);
        scene.setFill(Color.LIGHTGRAY);
        BorderPane sceneRoot = (BorderPane) scene.getRoot();

        TreeTableColumn<Employee, String> empColumn = new TreeTableColumn<>("Employee");
        empColumn.setPrefWidth(150);
        empColumn.setCellValueFactory(
                (TreeTableColumn.CellDataFeatures<Employee, String> param) -> new ReadOnlyStringWrapper(
                        param.getValue().getValue().getName()));

        TreeTableColumn<Employee, String> emailColumn = new TreeTableColumn<>("Email");
        emailColumn.setPrefWidth(190);
        emailColumn.setCellValueFactory(
                (TreeTableColumn.CellDataFeatures<Employee, String> param) -> new ReadOnlyStringWrapper(
                        param.getValue().getValue().getEmail()));

        TreeTableView<Employee> treeTableView = new TreeTableView<>(root);
        treeTableView.getColumns().setAll(empColumn, emailColumn);
        treeTableView.getColumns().stream().forEach((column) -> {
            createDragableColumnHeader(column);
        });

        HBox dndPane = new HBox();
        Label dragSource = new Label("<- drag me or a column there");
        dragSource.setOnDragDetected(new EventHandler<MouseEvent>() {
            public void handle(MouseEvent event) {
                Dragboard db = dragSource.startDragAndDrop(TransferMode.COPY);

                ClipboardContent content = new ClipboardContent();
                content.putString("dragged the Label");
                db.setContent(content);

                event.consume();
            }
        });

        /*
         * this does not work if an column is dragged... only events outside of
         * columns are used - which does not make sense as usually the columns
         * cover the whole area
         */
        treeTableView.setOnDragDetected(new EventHandler<MouseEvent>() {
            public void handle(MouseEvent event) {
                Dragboard db = dragSource.startDragAndDrop(TransferMode.COPY);

                ClipboardContent content = new ClipboardContent();
                content.putString("dragged the Table ");
                db.setContent(content);

                event.consume();
            }
        });

        Label dropTarget = new Label("[drop on me!]");

        dropTarget.setOnDragOver(new EventHandler<DragEvent>() {
            public void handle(DragEvent event) {
                if (event.getGestureSource() != dropTarget && event.getDragboard().hasString()) {
                    event.acceptTransferModes(TransferMode.COPY);
                }

                event.consume();
            }
        });
        dropTarget.setOnDragEntered(new EventHandler<DragEvent>() {
            public void handle(DragEvent event) {
                if (event.getGestureSource() != dropTarget && event.getDragboard().hasString()) {
                    dropTarget.setStyle("-fx-background-color: green;");
                }

                event.consume();
            }
        });
        dropTarget.setOnDragExited(new EventHandler<DragEvent>() {
            public void handle(DragEvent event) {
                dropTarget.setStyle("");

                event.consume();
            }
        });
        dropTarget.setOnDragDropped(new EventHandler<DragEvent>() {
            public void handle(DragEvent event) {
                Dragboard db = event.getDragboard();
                boolean success = false;
                if (db.hasString()) {
                    dropTarget.setText(db.getString());
                    success = true;
                }
                event.setDropCompleted(success);
                event.consume();
            }
        });

        dndPane.getChildren().addAll(dropTarget, dragSource);

        sceneRoot.setTop(dndPane);
        sceneRoot.setCenter(treeTableView);
        stage.setScene(scene);
        stage.show();
    }

    private void createDragableColumnHeader(TreeTableColumn column) {
        Label dragableHeader = new Label("[" + column.getText() + "]");
        dragableHeader.setStyle("-fx-background-color: red;");
        column.setText(null);
        column.setGraphic(dragableHeader);
        dragableHeader.setOnDragDetected(new EventHandler<MouseEvent>() {
            public void handle(MouseEvent event) {
                Dragboard db = dragableHeader.startDragAndDrop(TransferMode.COPY);

                ClipboardContent content = new ClipboardContent();
                content.putString("dragged the Column " + dragableHeader.getText());
                db.setContent(content);

                event.consume();
            }
        });
        dragableHeader.setOnDragDone(new EventHandler<DragEvent>() {
            public void handle(DragEvent event) {
                System.out.println("dropped. done! - how to fix nasty drag gfx?");
                event.consume();
            }
        });

    }

    public class Employee {
        private SimpleStringProperty name;
        private SimpleStringProperty email;

        public SimpleStringProperty nameProperty() {
            if (name == null) {
                name = new SimpleStringProperty(this, "name");
            }
            return name;
        }

        public SimpleStringProperty emailProperty() {
            if (email == null) {
                email = new SimpleStringProperty(this, "email");
            }
            return email;
        }

        private Employee(String name, String email) {
            this.name = new SimpleStringProperty(name);
            this.email = new SimpleStringProperty(email);
        }

        public String getName() {
            return name.get();
        }

        public void setName(String fName) {
            name.set(fName);
        }

        public String getEmail() {
            return email.get();
        }

        public void setEmail(String fName) {
            email.set(fName);
        }
    }
}