@objc func addNote() {
        let alert = UIAlertController(title: "Notiz hinzufügen", message: "", preferredStyle: UIAlertController.Style.alert )
        let save = UIAlertAction(title: "Fertig", style: .default) { (alertAction) in
            let textField = alert.textFields![0] as UITextField
            if textField.text != "" {
                self.notes = self.notes + [textField.text!];
            } else {
                // TF ist leer
            }

            self.tableView.reloadData();
        }
        alert.addTextField { (textField) in
            textField.placeholder = "Notiz"
        }

        alert.addAction(save);
        let cancel = UIAlertAction(title: "Abbrechen", style: .cancel) { (alertAction) in };
        alert.addAction(cancel);
        self.present(alert, animated:true, completion: nil);
    }