搜索栏问题ios 11，刷新控制

Question

我正在向tableView添加刷新控件。

然后从顶部的代码dosent show开始设置动画。我必须滚动tableView向下。

在此之后我将搜索控件添加到navbaritem，然后它看起来像：

这是代码

lazy var customRefreshControl: UIRefreshControl = {
    let control = UIRefreshControl()
    control.attributedTitle = NSAttributedString(string: "Downloading Locations")
    control.addTarget(self, action: #selector(updateLocation), for: .valueChanged)
    return control
}()
    override func viewDidLoad() {
    super.viewDidLoad()
    navigationItem.largeTitleDisplayMode = .automatic
    searchController = UISearchController(searchResultsController: nil)
    searchController.searchBar.tintColor = .white
    searchController.searchBar.delegate = self
    tableView.addSubview(customRefreshControl)
    title = "location_groups".localized()
    tableView.tableFooterView = UIView()
    tableView.backgroundColor = .groupTableViewBackground
    navigationItem.searchController = searchController
    searchController.dimsBackgroundDuringPresentation = false
}

    func loadLocationGroups() {
    DispatchQueue.global(qos: .userInteractive).async { [unowned self] in
        self.locationGroups = DataBaseManager.Instance.GetLocations()
        DispatchQueue.main.async {
            self.tableView.reloadData()
            if self.locationGroups.isEmpty {
                self.customRefreshControl.attributedTitle = NSAttributedString(string: "Downloading Locations")
            } else {
                self.customRefreshControl.attributedTitle = NSAttributedString(string: "Synchronize")
            }
            self.customRefreshControl.beginRefreshing()
        }
        self.request(requestType: .getLocationGroups)
    }
}