When a TreeItem that has a parent is set as the root node for a TreeView the x position of the root node is the same as if it was placed inside its parent.

This code shows the behaviour:


import java.util.*;

import javafx.application.Application;
import javafx.event.*;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class TreeViewApp extends Application {

    static int pos = 0;

    public TreeViewApp() {
        // TODO Auto-generated constructor stub
    }

    public static void main(final String[] args) {
        Application.launch(args);
    }

    @Override public void start(final Stage stage) throws Exception {
        final VBox box = new VBox();
        final TreeView<String> view = new TreeView<String>();
        final List<TreeItem<String>> items = new ArrayList<TreeItem<String>>();
        for (int i = 0; i < 10; i++) {
            final TreeItem<String> item = new TreeItem<String>("Item" + i);
            item.setExpanded(true);
            items.add(item);
        }
        for (int i = 0; i < 9; i++) {
            items.get(i).getChildren().add(items.get(i + 1));
        }
        view.setRoot(items.get(0));

        final Button button = new Button("Shift");
        button.setOnAction(new EventHandler<ActionEvent>() {

            @Override public void handle(final ActionEvent arg0) {
                if (pos < 9) {
                    view.setRoot(items.get(++pos));
                } else {
                    pos = 0;
                    view.setRoot(items.get(0));
                }
            }
        });
        box.getChildren().add(button);
        box.getChildren().add(view);
        stage.setScene(new Scene(box));
        stage.show();
    }
}