RootViewController

RootViewController.java

public class RootViewController implements Initializable {

    @FXML
    Pane root;

    @FXML
    Pane view1;

    @FXML
    Pane view2;

    @FXML
    ViewController view1Controller;

    @FXML
    ViewController view2Controller;

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        view1Controller.button.setOnAction(e -> root.getChildren().setAll(view2));
        view2Controller.button.setOnAction(e -> root.getChildren().setAll(view1));
        root.getChildren().setAll(view1);
    }

}