JavaFX和Swing拖放

Question

该程序包括两个部分。第一部分是Java Swing代码，它允许拖放String类型。

    listModel.addElement("Martha Washington");
    listModel.addElement("Abigail Adams");
    listModel.addElement("Martha Randolph");
    listModel.addElement("Dolley Madison");
    listModel.addElement("Elizabeth Monroe");
    listModel.addElement("Louisa Adams");
    listModel.addElement("Emily Donelson");
    list = new JList(listModel);
    list.setVisibleRowCount(-1);
    list.getSelectionModel().setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);

    list.setTransferHandler(new TransferHandler() {
        public boolean canImport(TransferHandler.TransferSupport info) {
            if (!info.isDataFlavorSupported(DataFlavor.stringFlavor)) {
                return false;
            }
            JList.DropLocation dl = (JList.DropLocation) info.getDropLocation();
            if (dl.getIndex() == -1) {
                return false;
            }
            return true;
        }
        public boolean importData(TransferHandler.TransferSupport info) {
            if (!info.isDrop()) {
                return false;
            }
            if (!info.isDataFlavorSupported(DataFlavor.stringFlavor)) {
                displayDropLocation("List doesn't accept a drop of this type.");
                return false;
            }

            JList.DropLocation dl = (JList.DropLocation) info.getDropLocation();
            DefaultListModel listModel = (DefaultListModel) list.getModel();
            int index = dl.getIndex();
            boolean insert = dl.isInsert();
            String value = (String) listModel.getElementAt(index);
            Transferable t = info.getTransferable();
            String data;
            try {
                data = (String) t.getTransferData(DataFlavor.stringFlavor);
            } catch (Exception e) {
                return false;
            }
            String dropValue = "\"" + data + "\" dropped ";
            if (dl.isInsert()) {
                if (dl.getIndex() == 0) {
                    displayDropLocation(dropValue + "at beginning of list");
                } else if (dl.getIndex() >= list.getModel().getSize()) {
                    displayDropLocation(dropValue + "at end of list");
                } else {
                    String value1 = (String) list.getModel().getElementAt(dl.getIndex() - 1);
                    String value2 = (String) list.getModel().getElementAt(dl.getIndex());
                    displayDropLocation(dropValue + "between \"" + value1 + "\" and \"" + value2 + "\"");
                }
            } else {
                displayDropLocation(dropValue + "on top of " + "\"" + value + "\"");
            }
            return false;
        }
        public int getSourceActions(JComponent c) {
            return COPY;
        }

        protected Transferable createTransferable(JComponent c) {
            JList list = (JList) c;
            Object[] values = list.getSelectedValues();

            StringBuffer buff = new StringBuffer();

            for (int i = 0; i < values.length; i++) {
                Object val = values[i];
                buff.append(val == null ? "" : val.toString());
                if (i != values.length - 1) {
                    buff.append("\n");
                }
            }
            return new StringSelection(buff.toString());
        }
    });

第二部分是JavaFX代码：

pane.setOnDragDetected(event -> {
            Dragboard db = pane.startDragAndDrop(TransferMode.ANY);
            ClipboardContent content = new ClipboardContent();
            content.putString("hallo");
            db.setContent(content);
            event.consume();
        });

    pane.setOnDragOver(event -> {
            final Dragboard dragboard;
            dragboard = event.getDragboard();
            if (dragboard.hasString()){
                event.acceptTransferModes(TransferMode.ANY);
                System.out.println(dragboard.getString());
            }
            event.consume();
        });

    pane.setOnDragDropped(event -> {
            /* data dropped */
            /* if there is a string data on dragboard, read it and use it */
            Dragboard db = event.getDragboard();
            boolean success = false;
            if (db.hasString()) {
                String data = db.getString();
                label.setText(data);
                SwingUtilities.invokeLater(() -> showStatus(data, "JavaFX"));
                success = true;
            }
            event.setDropCompleted(success);
            event.consume();
        });

将字符串从JavaFx组件拖动到Swing效果很好，但是swing无法接受从Swing拖动字符串。当我使用dragboard.getString（）在方法setOnDragOver（）中打印字符串时，它为null。

如何解决此问题？非常感谢。