protected void createdirButtonAction(ActionEvent event){
        String filename = filenameField.textProperty().get();
        TreeItem<File> selected = treeView.getSelectionModel().getSelectedItem();
        if (selected.getValue().isDirectory() && !filename.isEmpty()) {
            Path p = Paths.get(selected.getValue().toString(), filename);
            try {
                Files.createDirectory(p);
            } catch (IOException ex) {
                System.err.println("Blad przy dodawaniu pliku " + ex);
            }
            TreeItem newFile = new TreeItem<Path>(p);
            selected.getChildren().add(newFile);
        }
    }