TreeTableView drag and drop - javafx

Question

I'm using a TreeTableView to display the content of a tree. The sorting order in the tree is manual, and I want to be able to drag and drop items.
How can I drag and drop items in a TreeTableView?

Answer 1

One way is to us a 'treeTableView.setRowFactory'. In the 'call' method, you create a row, to which you attach the 'onDragDetected', 'onDragDropped' etc. See example below.
// Create the root, RowContainer is your class contianing row attributes
TreeItem<RowContainer> rootTIFX = new TreeItem<RowContainer>(rowContainerRoot);
// Add leaves under your root.
...
// Create the row factory
treeTableView.setRowFactory(new Callback<TreeTableView, TreeTableRow<RowContainer>>() {
#Override
public TreeTableRow<RowContainer> call(final TreeTableView param) {
final TreeTableRow<RowContainer> row = new TreeTableRow<RowContainer>();
row.setOnDragDetected(new EventHandler<MouseEvent>() {
#Override
public void handle(MouseEvent event) {
// drag was detected, start drag-and-drop gesture
TreeItem<RowContainer> selected = (TreeItem<RowContainer>) treeTableView.getSelectionModel().getSelectedItem();
// to access your RowContainer use 'selected.getValue()'
if (selected != null) {
Dragboard db = treeTableView.startDragAndDrop(TransferMode.ANY);
// create a miniature of the row you're dragging
db.setDragView(row.snapshot(null, null));
// Keep whats being dragged on the clipboard
ClipboardContent content = new ClipboardContent();
content.putString(selected.getValue().getName());
db.setContent(content);
event.consume();
}
}
});
row.setOnDragOver(new EventHandler<DragEvent>() {
#Override
public void handle(DragEvent event) {
// data is dragged over the target
Dragboard db = event.getDragboard();
if (event.getDragboard().hasString()){
event.acceptTransferModes(TransferMode.MOVE);
}
event.consume();
}});
row.setOnDragDropped(new EventHandler<DragEvent>() {
#Override
public void handle(DragEvent event) {
Dragboard db = event.getDragboard();
boolean success = false;
if (event.getDragboard().hasString()) {
if (!row.isEmpty()) {
// This is were you do your magic.
// Move your row in the tree etc
// Here is two examples of how to access
// the drop destination:
int dropIndex = row.getIndex();
TreeItem<RowContainer> droppedon = row.getTreeItem();
success = true;
}
}
event.setDropCompleted(success);
event.consume();
}});
return row;
}
});