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)")
    }

对于Swift 5，我们可以检查它在视图中是否会消失

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

    if self.isMovingFromParent {
        delegate?.passValue(clickedImage: selectedImage)
    }
}

将按钮替换为另一个答案中建议的自定义按钮可能不是一个好主意，因为您将失去默认的行为和样式。

另一个选择是在视图控制器上实现viewWillDisappear方法，并检查名为isMovingFromParentViewController的属性。如果那个属性为真，它意味着视图控制器正在消失，因为它正在被移除(弹出)。

应该是这样的:

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

    if self.isMovingFromParentViewController {
        // Your code...
    }
}

在swift 4.2中

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

    if self.isMovingFromParent {
        // Your code...
    }
}

我的偏好是在导航控制器中覆盖popViewController。这样做的好处是:

你的应用程序保持默认的后退按钮外观和动画，你不需要管理它。如果用户在手机上设置了大号文本，这尤其有用，因为默认的后退按钮会根据用户的设置增加或减少大小。 你可以完全停止视图弹出，不像使用viewWillDisappear。

首先，创建一个自定义导航控制器类(并确保将其分配给故事板中的导航控制器或任何创建导航控制器的地方):

class NavControllerWithBackButtonOverride: UINavigationController {

    var backButtonOverride: (() -> Void)? = nil

    override func popViewController(animated: Bool) -> UIViewController? {

        if backButtonOverride != nil {
            //if anything is assigned to the backButtonOverride the override will run
            self.backButtonOverride!()
            return nil
        } else {
            //otherwise the default popViewController will run
            return super.popViewController(animated: animated)
        }
    }
}

然后通过给backButtonOverride变量赋值，在视图控制器中启用/禁用重载:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    self.enableCustomBackButton()
}

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

/**
 Custom Back Button
 */

func customBackButtonAction() {
    print("DO THIS INSTEAD")
}

func enableCustomBackButton() {
    if let nav = self.navigationController as? NavControllerWithBackButtonOverride {
        nav.backButtonOverride = { self.customBackButtonAction() }
        nav.interactivePopGestureRecognizer?.isEnabled = false
    }    
}

func disableCustomBackButton() {
    if let nav = self.navigationController as? NavControllerWithBackButtonOverride {
    nav.backButtonOverride = nil
    nav.interactivePopGestureRecognizer?.isEnabled = true
    }
}

注意:我还禁用了interactivePopGestureRecognizer，因为它会导致自定义设置的问题。

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)
}

在Swift 5和Xcode 10.2中

请不要添加自定义栏按钮项，使用默认行为。

不需要viewWillDisappear，不需要自定义BarButtonItem等…

最好是检测VC何时从其父对象中移除。

使用这两个函数中的任意一个

override func willMove(toParent parent: UIViewController?) {
    super.willMove(toParent: parent)
    if parent == nil {
        callStatusDelegate?.backButtonClicked()//Here write your code
    }
}

override func didMove(toParent parent: UIViewController?) {
    super.didMove(toParent: parent)
    if parent == nil {
        callStatusDelegate?.backButtonClicked()//Here write your code
    }
}

如果你想停止返回按钮的默认行为，然后添加自定义BarButtonItem。