如果你想有后退按钮和后退箭头，你可以使用下面的图片和代码

backArrow.png backArrow@2x.png backArrow@3x.png

override func viewDidLoad() {
    super.viewDidLoad()
    let customBackButton = UIBarButtonItem(image: UIImage(named: "backArrow") , style: .plain, target: self, action: #selector(backAction(sender:)))
    customBackButton.imageInsets = UIEdgeInsets(top: 2, left: -8, bottom: 0, right: 0)
    navigationItem.leftBarButtonItem = customBackButton
}

func backAction(sender: UIBarButtonItem) {
    // custom actions here
    navigationController?.popViewController(animated: true)
}

这并不像我们想象的那么难。只需要为UIButton创建一个背景颜色清晰的框架，为按钮分配动作，并放置在导航栏后退按钮上。最后在使用后取下按钮。

这是Swift 3 用UIImage代替UIButton的示例代码

override func viewDidLoad() {
    super.viewDidLoad()
    let imageView = UIImageView()
    imageView.backgroundColor = UIColor.clear
    imageView.frame = CGRect(x:0,y:0,width:2*(self.navigationController?.navigationBar.bounds.height)!,height:(self.navigationController?.navigationBar.bounds.height)!)
    let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(back(sender:)))
    imageView.isUserInteractionEnabled = true
    imageView.addGestureRecognizer(tapGestureRecognizer)
    imageView.tag = 1
    self.navigationController?.navigationBar.addSubview(imageView)
    }

编写需要执行的代码

func back(sender: UIBarButtonItem) {

    // Perform your custom actions}
    _ = self.navigationController?.popViewController(animated: true)

    }

执行操作后删除子视图

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)

    for view in (self.navigationController?.navigationBar.subviews)!{
        if view.tag == 1 {
            view.removeFromSuperview()
        }
    }

Swift 5+(带警报控制的后退按钮)

override func viewDidLoad() {
        super.viewDidLoad()
        
        self.navigationItem.hidesBackButton = true
        let newBackButton = UIBarButtonItem(title: "<Back", style: UIBarButtonItem.Style.plain, target: self, action: #selector(PGWebViewController.back(sender:)))
        self.navigationItem.leftBarButtonItem = newBackButton
}


@objc func back(sender: UIBarButtonItem) {
    
    let alert = UIAlertController(title: "Warning!", message: "Your payment process is not completed yet. Do you want to go back?", preferredStyle: .alert)
        
         let ok = UIAlertAction(title: "OK", style: .default, handler: { action in
             _ = self.navigationController?.popViewController(animated: true)
         })
         alert.addAction(ok)
         let cancel = UIAlertAction(title: "Cancel", style: .default, handler: { action in
         })
         alert.addAction(cancel)
         DispatchQueue.main.async(execute: {
            self.present(alert, animated: true)
    })}

NO

override func willMove(父控件:UIViewController?) {}

即使你在segue到覆盖这个方法的视图控制器，这个也会被调用。其中，检查parent是否为nil或not不是确保移动回正确的UIViewController的精确方法。为了准确地确定UINavigationController是否正确地导航回呈现当前的UIViewController，你将需要遵守UINavigationControllerDelegate协议。

YES

注意:MyViewController只是你想要检测返回的UIViewController的名称。

1)在你的文件顶部添加UINavigationControllerDelegate。

class MyViewController: UIViewController, UINavigationControllerDelegate {

2)添加一个属性到你的类，它将跟踪你正在segue的UIViewController。

class MyViewController: UIViewController, UINavigationControllerDelegate {

var previousViewController:UIViewController

3)在MyViewController的viewDidLoad方法中为你的UINavigationController分配self作为委托。

override func viewDidLoad() {
    super.viewDidLoad()
    self.navigationController?.delegate = self
}

3)在你segue之前，将之前的UIViewController分配为这个属性。

// In previous UIViewController
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "YourSegueID" {
        if let nextViewController = segue.destination as? MyViewController {
            nextViewController.previousViewController = self
        }
    }
}

4)并遵循UINavigationControllerDelegate的MyViewController中的一个方法

func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
    if viewController == self.previousViewController {
        // You are going back
    }
}

这里有一个最简单的Swift 5解决方案，它不需要你创建一个自定义的后退按钮，也不需要你放弃所有免费获得的UINavigationController左键功能。

正如Brandon A上面建议的那样，你需要在你想要与之交互的视图控制器中实现UINavigationControllerDelegate。一个好方法是创建一个unwind segue，你可以手动或自动地执行，并从自定义完成按钮或后退按钮重用相同的代码。

首先，让你感兴趣的视图控制器(你想检测返回的那个)在它的viewDidLoad中成为导航控制器的委托:

override func viewDidLoad() {
    super.viewDidLoad()
    navigationController?.delegate = self
}

其次，在文件底部添加一个扩展，覆盖navigationController(willShow:animated:)

extension PickerTableViewController: UINavigationControllerDelegate {

    func navigationController(_ navigationController: UINavigationController,
                              willShow viewController: UIViewController,
                              animated: Bool) {

        if let _ = viewController as? EditComicBookViewController {

            let selectedItemRow = itemList.firstIndex(of: selectedItemName)
            selectedItemIndex = IndexPath(row: selectedItemRow!, section: 0)

            if let selectedCell = tableView.cellForRow(at: selectedItemIndex) {
                performSegue(withIdentifier: "PickedItem", sender: selectedCell)
            }
        }
    }
}

因为你的问题包含了一个UITableViewController，所以我包含了一种获取用户点击行的索引路径的方法。

Swift 5 __ Xcode 11.5

在我的情况下，我想做一个动画，当它完成后，返回。 一种覆盖后退按钮默认动作的方法 调用你的自定义动作是这样的:

     override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        setBtnBack()
    }

    private func setBtnBack() {
        for vw in navigationController?.navigationBar.subviews ?? [] where "\(vw.classForCoder)" == "_UINavigationBarContentView" {
            print("\(vw.classForCoder)")
            for subVw in vw.subviews where "\(subVw.classForCoder)" == "_UIButtonBarButton" {
                let ctrl = subVw as! UIControl
                ctrl.removeTarget(ctrl.allTargets.first, action: nil, for: .allEvents)
                ctrl.addTarget(self, action: #selector(backBarBtnAction), for: .touchUpInside)
            }
        }
    }


    @objc func backBarBtnAction() {
        doSomethingBeforeBack { [weak self](isEndedOk) in
            if isEndedOk {
                self?.navigationController?.popViewController(animated: true)
            }
        }
    }


    private func doSomethingBeforeBack(completion: @escaping (_ isEndedOk:Bool)->Void ) {
        UIView.animate(withDuration: 0.25, animations: { [weak self] in
            self?.vwTxt.alpha = 0
        }) { (isEnded) in
            completion(isEnded)
        }
    }

或者你可以使用这个方法一次来探索NavigationBar视图层次结构，并获得访问_UIButtonBarButton视图的索引，转换为UIControl，删除目标-动作，并添加你的自定义目标-动作:

    private func debug_printSubviews(arrSubviews:[UIView]?, level:Int) {
        for (i,subVw) in (arrSubviews ?? []).enumerated() {
            var str = ""
            for _ in 0...level {
                str += "\t"
            }
            str += String(format: "%2d %@",i, "\(subVw.classForCoder)")
            print(str)
            debug_printSubviews(arrSubviews: subVw.subviews, level: level + 1)
        }
    }

    // Set directly the indexs
    private func setBtnBack_method2() {
        // Remove or comment the print lines
        debug_printSubviews(arrSubviews: navigationController?.navigationBar.subviews, level: 0)   
        let ctrl = navigationController?.navigationBar.subviews[1].subviews[0] as! UIControl
        print("ctrl.allTargets: \(ctrl.allTargets)")
        ctrl.removeTarget(ctrl.allTargets.first, action: nil, for: .allEvents)
        print("ctrl.allTargets: \(ctrl.allTargets)")
        ctrl.addTarget(self, action: #selector(backBarBtnAction), for: .touchUpInside)
        print("ctrl.allTargets: \(ctrl.allTargets)")
    }