@FXML
  public void onDragDroppedFolder(DragEvent event) {
    Dragboard dragboard = event.getDragboard();

    File folder = dragboard.getFiles().get(0);

    DestinationFolder dest = new DestinationFolder(folder);

    if (this.repository.existsSameFolder(dest)) {
      Alert alert = new Alert(AlertType.ERROR);
      alert.setTitle("エラー");
      alert.setHeaderText("既にフォルダが登録されています。");
      alert.getDialogPane().setContentText(dest.getDestPath());
      alert.show();
    } else {
      TextInputDialog dialog = new TextInputDialog();
      dialog.setTitle("フォルダ追加");
      dialog.setContentText("フォルダ名");
      dialog.setHeaderText(dest.getDestPath());
      dialog.getEditor().setText(dest.getName());

      dialog.setOnCloseRequest(
          e -> {
            TextInputDialog d = (TextInputDialog) e.getTarget();
            String result = d.getResult();

            if (result != null) {
              if (result.isEmpty()) {
                Alert alert = new Alert(AlertType.ERROR);
                alert.setTitle("エラー");
                alert.setHeaderText("フォルダ名に空は指定できません。");
                alert.show();
              } else {
                dest.setName(result);
                this.repository.registerFolder(dest);
                this.destinationFolders = repository.findAll();
                this.refreshDestFolderListView();
              }
            }
          });

      dialog.show();
    }

    event.setDropCompleted(true);
    event.consume();
  }
 @Override
 public void initialize(URL location, ResourceBundle resources) {
   this.destinationFolders = repository.findAll();
   this.refreshDestFolderListView();
   this.clear();
 }