TornadoFX Drag and Drop on a TreeView - tornadofx

Question

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.

Answer 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 ->
}
}
}
}