To reproduce:

1. Expand all nodes.
2. Push Ctrl + A.
3. Click button.

Focused item is "Item 2 3"
But it's hidden from viewable area.

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.SelectionMode;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class TreeViewFocus extends Application {

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

    @Override
    public void start(Stage stage) throws Exception {

        HBox root = new HBox(10d);

        final TreeView<String> treeView = new TreeView<>();
        treeView.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);

        TreeItem rootItem = new TreeItem("ROOT");
        treeView.setRoot(rootItem);

        for (int i = 0; i < 3; i++) {
            TreeItem parent = new TreeItem("Item " + i);
            rootItem.getChildren().add(parent);

            for (int j = 0; j < 4; j++) {
                TreeItem childItem = new TreeItem("Item " + i + " " + j);
                parent.getChildren().add(childItem);
            }
        }

        root.getChildren().add(treeView);

        Label lblFocusedItemHeader = new Label("Focused item: ");
        final Label lblFocusedItem = new Label();

        HBox hbFocusedItem = new HBox();
        
        Button btnGetSelectedItem = new Button("Show focused item");
        btnGetSelectedItem.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent t) {
                lblFocusedItem.setText(treeView.getFocusModel().getFocusedItem().getValue());
            }
        });

        hbFocusedItem.getChildren().addAll(btnGetSelectedItem, lblFocusedItemHeader, lblFocusedItem);
        root.getChildren().add(hbFocusedItem);

        Scene scene = new Scene(root, 600, 300);
        stage.setScene(scene);
        stage.show();
    }
}