TreeView using Drag and Drop incorrect getGestureSource() - javafx-8

Question

I have a simple tree view with drag and drop enabled. But, on setOnDragOver() call, I receive event with gesture source. The source got is not the cell that starts the dragging (via setOnDragDetected() call), but the pane that contains the tree view. What am I missing ?
My code is shown below:
tree.setCellFactory(
new Callback<TreeView<String>, TreeCell<String>>() {
#Override
public TreeCell<String> call(
final TreeView<String> param) {
TreeCell<String> treeCell =
new TreeCell<String>() {
#Override
protected void updateItem(
final String value,
final boolean empty) {
super.updateItem(value, empty);
if (!empty && (value != null)) {
setText(value);
setGraphic(getTreeItem().getGraphic());
} else {
setText(null);
setGraphic(null);
}
}
};
treeCell.setOnDragDetected(event -> {
Dragboard dragBoard =
startDragAndDrop(TransferMode.MOVE);
ClipboardContent content = new ClipboardContent();
content.putString(treeCell.getTreeItem().getValue());
dragBoard.setContent(content);
event.consume();
});
treeCell.setOnDragOver(event -> {
// Here is I've got pane instead of cell
Object source = event.getGestureSource();
if ((event.getGestureSource() != treeCell)
&& event.getDragboard().hasString()) {
event.acceptTransferModes(TransferMode.MOVE);
}
event.consume();
});
return treeCell;
}
});

Answer 1

The gesture source is the node on which startDragAndDrop(...) was called; you are calling it on whatever node instance you are currently in (I guess you have some custom subclass of Pane, or something).
So you need
treeCell.setOnDragDetected(event -> {
Dragboard dragBoard =
treeCell.startDragAndDrop(TransferMode.MOVE);
// ...
});