JavaFX: How to find index of TreeItem in a TreeView?

Question

I have a TreeView and a Button in my program. Whenever this Button is clicked, it adds a new element right after the element selected last in the TreeView.

For example, if I were to select the "Test Action" element and click the "Add" button, it should add another TreeItem right after "Test Action", but before "Test Condition".

I've written code so that I can keep track of the element selected last:

@FXML
TreeView<String> view;
TreeItem<String> current = root;
view.selectionModelProperty().addListener(new ChangeListener<MultipleSelectionModel<TreeItem<String>>>() {

            @Override
            public void changed(ObservableValue<? extends MultipleSelectionModel<TreeItem<String>>> observable,
                    MultipleSelectionModel<TreeItem<String>> oldValue,
                    MultipleSelectionModel<TreeItem<String>> newValue) {
                    current = newValue.getSelectedItem();
            }
});

However, through the use of the TreeItem, "current", there is no method I can use to find its index in the TreeView.

This is so that I can do:

root.getChildren().add(index, new TreeItem<String>(new OpenBank().getAction(), Icons.ACTION.getIcon()));

So is there a way to find a child's index in a TreeView ?

Answer 1

The class TreeItem has a method getParent , which returns the parent of the specified TreeItem . This parent, which is also a TreeItem has a method getChildren to get the child TreeItem s; the order of TreeItem s in the returned ObservableList is the actual order that you can see on the screen, therefore you can insert a new element in a specific index with add after you retrieved the index of the element in the list with indexOf() .

You can simply handle the current selection in the event listener of your Button :

Button b = new Button("Add");
b.setOnAction(event -> {
    // Get the selected item
    TreeItem<String> selectedItem = treeView.getSelectionModel().getSelectedItem();

    // If there is no selection or the root is selected do nothing
    if (selectedItem == null || selectedItem == rootNode)
        return;

    // Otherwise get the index of the Node from the children of its parent
    // and append the new item right after it
    int index = selectedItem.getParent().getChildren().indexOf(selectedItem);
    selectedItem.getParent().getChildren().add(index+1, new TreeItem<>("New Item"));
});

If you already tracking the current selection:

The modification is just to use current (that's how you named your variable) rather than getting the selection in the handler:

Button b = new Button("Add");
b.setOnAction(event -> {
    // If there is no selection or the root is selected do nothing
    if (current == null || current == rootNode)
        return;

    // Otherwise get the index of the Node from the children of its parent
    // and append the new item right after it
    int index = current.getParent().getChildren().indexOf(current);
    current.getParent().getChildren().add(index+1, new TreeItem<>("New Item"));
});

Answer 2

TreeItem::getRow

Returns the index position of the given TreeItem, assuming that it is currently accessible through the tree hierarchy (most notably, that all parent tree items are expanded). If a parent tree item is collapsed, the result is that this method will return -1 to indicate that the given tree item is not accessible in the tree.