取消按钮不显示，用户点击搜索栏时无法调用该功能

Question

点击取消按钮所在的区域会导致调用取消按钮功能，但是取消按钮本身不可见。像在输入文本之前一样轻按搜索栏会导致搜索栏升高，但是它不会调用任何委托函数，因此我无法对ui进行必要的调整。另外，点击搜索栏会使我的表视图消失，原因不明。

private func configureSearchBar() {
    searchController.searchResultsUpdater = self
    searchController.dimsBackgroundDuringPresentation = false
    searchController.searchBar.showsCancelButton = true
    searchController.searchBar.delegate = self
    definesPresentationContext = true
    searchController.obscuresBackgroundDuringPresentation = false
    view.addSubview(searchController.searchBar)
    searchController.searchBar.frame = CGRect(x: 20, y: topBarHeight * 1.65, width: self.view.bounds.width - 40, height: 55)
    let color:UIColor = .forestGreen
    let lightForestGreen = color.withAlphaComponent(0.5)
    searchController.searchBar.tintColor = lightForestGreen
    searchController.searchBar.barTintColor = lightForestGreen
    searchController.searchBar.backgroundColor = lightForestGreen
    searchController.searchBar.layer.borderColor = lightForestGreen.cgColor
    navigationItem.hidesSearchBarWhenScrolling = false
    searchController.hidesNavigationBarDuringPresentation = true
    searchController.searchBar.text = ""
    searchController.searchBar.setShowsCancelButton(true, animated: false)
}


//cancel button not visible, but tapping on that area calls this function below:

func searchBarCancelButtonClicked(_ searchBar: UISearchBar) {
    print("cancel button clicked...")
    agendaLabel.isHidden = false
    navigationController?.navigationBar.isHidden = true
    tableView.reloadData()
}

//在搜索栏上点击会使其移动到屏幕顶部，但无法调用以下任何功能：

extension ScheduleViewController: UISearchBarDelegate {

func searchBar(_ searchBar: UISearchBar, selectedScopeButtonIndexDidChange selectedScope: Int) {
    agendaLabel.isHidden = true
    tableView.isHidden = false
}

func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
    agendaLabel.isHidden = true
    tableView.isHidden = false
}

func searchBarResultsListButtonClicked(_ searchBar: UISearchBar) {
    agendaLabel.isHidden = true
    tableView.isHidden = false
}

}