TornadoFX Drag and Drop on a TreeView

问题

I am new to JavaFX and, therefore, also to TornadoFX so please bear with me.

I have a simple app in Java but want to move it to Kotlin and am running into problems finding the corresponding mechanisms in TornadoFX. I have a ListView holding implementations of IStoryItem representing Stories and Chapters. I want to be able to move the chapters around and even from one story to another. The TreeView in Java has the following implementation in its setCellFactory call:

    tv.setCellFactory(new Callback<TreeView<IStoryItem>, TreeCell<IStoryItem>>() {
        @Override
        public TreeCell<IStoryItem> call(TreeView<IStoryItem> siTreeView) {
            TreeCell<IStoryItem> cell = new TreeCellStoryEditor();

            cell.setOnDragDetected((MouseEvent event) -> {
                // Don't drag Story nodes.
                if (cell.getItem() instanceof Story) return;

                Dragboard db = cell.startDragAndDrop(TransferMode.MOVE);

                // Put the Part on the dragboard
                // From: https://stackoverflow.com/a/30916660/780350
                ClipboardContent content = new ClipboardContent();
                content.put(objectDataFormat, cell.getItem());
                db.setContent(content);

                event.consume();
            });

            cell.setOnDragOver((DragEvent event) -> {
                if (event.getGestureSource() != cell && event.getDragboard().hasContent(objectDataFormat)) {
                    /* allow for moving */
                    event.acceptTransferModes(TransferMode.MOVE);
                }

                event.consume();
            });

            cell.setOnDragEntered((DragEvent event) -> {
                IStoryItem item = cell.getItem();
                if (item instanceof Story &&
                        event.getGestureSource() != cell &&
                        event.getDragboard().hasContent(objectDataFormat)) {
                    cell.setUnderline(true);
                }

                event.consume();
            });

            cell.setOnDragExited((DragEvent event) -> {
                cell.setUnderline(false);
                event.consume();
            });

            cell.setOnDragDropped((DragEvent event) -> {
                try {
                    Dragboard db = event.getDragboard();
                    boolean success = false;
                    if (db.hasContent(objectDataFormat)) {
                        Part droppedPart = (Part)db.getContent(objectDataFormat);
                        IStoryItem targetStoryItem = cell.getItem();

                        // Question: How to handle drops between leaf items or
                        // before the initial leaf or after the final leaf.
                        if (targetStoryItem instanceof Story) {
                            Story story = (Story) targetStoryItem;

                            updateStoryWith(droppedPart, story);
                            addPartTo(cell.getTreeItem(), droppedPart);
                            success = true;
                        }
                    }

                    event.setDropCompleted(success);
                    event.consume();
                } catch (Exception e) {
                    System.out.println(e.getMessage());
                }
            });

            cell.setOnDragDone((DragEvent event) -> {
                if (event.getTransferMode() == TransferMode.MOVE) {
                    IStoryItem item = cell.getItem();
                    TreeItem<IStoryItem> ti = cell.getTreeItem();
                    TreeItem<IStoryItem> pti = ti.getParent();
                    pti.getChildren().remove(ti);

                    IStoryItem psi = pti.getValue();
                    // Remove the Part/Chapter from its previous Story
                    boolean removed = removePartFrom(psi, item);
                }
                event.consume();
            });

            cell.setEditable(true);

            return cell;
        };
    });

I have looked for something similar in TornadoFX but can't find anything that looks like it would work. I am already using the cellFormat builder but I can't figure out how to add the event handlers inside it. I see from IntelliJ's intellisense that there is also a cellFactory builder but I am not sure how to make use of it or how to add the event handlers to it.

回答1:

You can use the exact same technique in TornadoFX. Remember, TornadoFX just applies a high level API on top of JavaFX. You can always still access the underlying JavaFX API's without issue.

tv.setCellFactory {
    object : TreeCell<IStoryItem>() {
        init {
            setOnDragOver { event ->

            }
            setOnDragEntered { event ->

            }
            setOnDragExited { event ->

            }
            setOnDragDropped { event ->

            }
        }
    }
}

来源：https://stackoverflow.com/questions/46182788/tornadofx-drag-and-drop-on-a-treeview