按下“返回”后，TableView单元格被导航覆盖？

所以我有一个导航栏下的tableview，当用户在搜索栏中输入内容时会显示出来。一切似乎都可以发现。但是当我推送一个视图控制器，当用户在tableview中选择一个单元格，然后从detailViewController返回时，我的tableview就搞砸了。按下“返回”后，TableView单元格被导航覆盖？

•问题：在按下detailViewController后，tableview的最顶端单元格被导航栏覆盖。但是这一开始并没有发生。

•我已经试过：

1. Toggled 'Under Top Bars' in the storyboard 
    2. Check all my constraint

这是实现代码如下如何添加到子视图

func updateSearchResults(for searchController: UISearchController) { 

    // When the user is typing 
    if let searchText = searchController.searchBar.text, !searchText.isEmpty { 

     // add the tableview onto the subview 
     view.addSubview(tableView) 

     self.searchController.dimsBackgroundDuringPresentation = false 

     // filter the username array, to match the text in the search bar 
     filteredUsernames = unfilterdUsernames.filter({ (username) -> Bool in 
      return username.lowercased().contains(searchText.lowercased()) 
     }) 

     if let usernames = filteredUsernames { 
      getUsersFromUsernames(usernames: usernames, completion: { (users) in 
       self.filteredUsers = users 
      }) 
     } 

     // else, the user is not typing anything. Remove the tableview from the subview 
    } else { 
     self.searchController.dimsBackgroundDuringPresentation = false 

     tableView.removeFromSuperview() 
     filteredUsernames = unfilterdUsernames 

    } 
    // reload tableview data 
    tableView.reloadData() 
}

我这是怎么搬进detailViewController：

tableView（_ tableView：UITableView， didSelectRowAt indexPath：IndexPath）

// the profile view that I want to display, after the user select one of the tableViewCell 
    let profileController = UIStoryboard(name: "Profile", bundle: nil).instantiateViewController(withIdentifier: "profile") as? ProfileCollectionViewController 

    // user is the value that I want to transfer to the profileController 
    // which user from the indexPath in tableView 
    if let user = filteredUsers?[indexPath.row] { 
     userToPass = user 
     // set the delegate to self 
     profileController?.userDataDelegate = self 
     // push a navigationController to profileController 
     self.navigationController?.pushViewController(profileController!, animated: true)

才去detailViewController：