Switching screen through an ImageView – Java FX

I’m working with SceneBuilder and JavaFX and I want to change screens by clicking on ImageViews, but my program it’s giving a few exceptions (not specified) in the main function, and on the SceneBuilder screen doesn’t show any ID for the ImageView.

public class PrincipalController implements Initializable {

    private Button imageView_principal;

    private Button imageView_funcionario;

    private Button imageView_departamento;

    private void goToFuncionario(ActionEvent event) throws IOException {
        //Mostrar janela seguinte
        Parent GerentePageParent = FXMLLoader.load(getClass().getResource("Funcionario.fxml"));
        Scene GerentePageScene = new Scene(GerentePageParent);
        Stage app_stage = (Stage) ((Node) event.getSource()).getScene().getWindow();


public class Projecto extends Application {

    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("Principal.fxml"));

        Scene scene = new Scene(root);


     * @param args the command line arguments
    public static void main(String[] args) {


My SceneBuilder:

SceneBuilder FXML:

SceneBuilder FXML

If anyone could help I would appreciate it. Thanks