键盘滚动到底部时如何使导航栏和表格视图位置固定？

Question

我正在使用底部有文本字段的tableview控制器。当它运行并且我单击文本字段时，整个页面滚动到底部，包括位于顶部的导航栏。我想要导航baR FIXED ON TOP并且表格视图的滚动位置保持不变。你能告诉我另一种改变tableview框架或其他方法的方法吗？我目前正在使用iOS 11.0进行测试，Xcode 9.1 swift 4

import UIKit
import GRDB
import IQKeyboardManagerSwift
import Alamofire
import SVProgressHUD
import UIEmptyState
import SwiftyJSON


class AssistantController: UIViewController , UITableViewDelegate , UITableViewDataSource , UITextFieldDelegate , UIEmptyStateDelegate , UIEmptyStateDataSource  {

    var user : User!
    var assist : [Assistant] = []

    @IBOutlet weak var tableView: UITableView!
    @IBOutlet weak var txtEmail : UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.tableFooterView = UIView.init()

        let btn2 = UIButton(type: .custom)
        btn2.setImage(UIImage(named: "back_arrow"), for: .normal)
        btn2.tintColor = UIColor.init(red: 219.0/255.0, green: 103.0/255.0, blue: 93.0/255.0, alpha: 1)
        btn2.frame = CGRect(x: 0, y: 0, width: 45, height: 45)
        btn2.addTarget(self, action: #selector(compopen(sender:)), for: .touchUpInside)
        let item2 : UIBarButtonItem  = UIBarButtonItem(customView: btn2)
        self.navigationItem.setLeftBarButton(item2, animated: true)
        self.navigationItem.title = "AssistMan".localized()
        self.navigationController?.setNavigationBarHidden(false, animated: true)
        txtEmail.placeholder = "Assistant Email (Optional)".localized()
        IQKeyboardManager.sharedManager().enableAutoToolbar = false


        txtEmail.delegate = self

        //txtEmail.becomeFirstResponder()

        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)

        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil)

        //tableView.isScrollEnabled = false
    }

    @objc func keyboardWillShow(_ notification:Notification) {

        var userInfo = notification.userInfo!
        var keyboardFrame:CGRect = (userInfo[UIKeyboardFrameBeginUserInfoKey] as! NSValue).cgRectValue
        if keyboardFrame.size.height <= 0 { // to fix bug on iOS 11
            keyboardFrame = (userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
        }
        keyboardFrame = self.view.convert(keyboardFrame, from: nil)
            tableView.frame = CGRect.init(x: 0, y: 0, width: self.view.frame.size.width, height: self.view.frame.size.height - keyboardFrame.height)

    }

    @objc func keyboardWillHide(_ notification:Notification) {

        tableView.frame = CGRect.init(x: 0, y: 0, width: self.view.frame.size.width, height: self.view.frame.size.height)
    }


    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        IQKeyboardManager.sharedManager().enableAutoToolbar = true
    }


    func textFieldShouldReturn(_ textField: UITextField) -> Bool { // called when 'return' key pressed. return {
        print("typed")
        textField.resignFirstResponder()
        // add
        //executeInsert ()
        return true
    }

    func executeInsert () {

        self.view.endEditing(true)
        let assistantEmail : String = txtEmail.text!
        if assistantEmail.isEmpty {
            SVProgressHUD.showError(withStatus:  "Please type your email".localized())
            SVProgressHUD.dismiss(withDelay: 2.0)
            return
        }


    }

    @IBAction func executeAdd(_ sender: Any) {
        executeInsert ()
    }


    @objc func compopen (  sender: UIBarButtonItem ) {
        self.navigationController?.popViewController(animated: true)
    }



    override func viewWillAppear(_ animated: Bool) {
        user  = User.sharedInstance
        enqueue(subUrl: "GetAssistant", inputDict: user.getAssist())
        getData()
    }


    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        if assist.isEmpty {
            self.reloadEmptyStateForTableView(self.tableView)
            //self.emptyStateView?.tintColor = UIColor.themeRed()
        }
    }


    func numberOfSections(in tableView: UITableView) -> Int {
        // #warning Incomplete implementation, return the number of sections
        return 1
    }

    func tableView(_ tableView: UITableView, titleForDeleteConfirmationButtonForRowAt indexPath: IndexPath) -> String? {
        return "刪除".localized()
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        // #warning Incomplete implementation, return the number of rows
        return assist.count
    }



}