我需要执行一个动作(清空一个数组),当UINavigationController的后退按钮被按下,而按钮仍然导致堆栈上的前一个ViewController出现。我如何使用swift来实现这一点?


当前回答

这就是我的解

extension UINavigationController: UINavigationBarDelegate {
    public func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
        if let shouldBlock = self.topViewController?.shouldPopFromNavigation() {
            return shouldBlock
        }
        return true
    }
}

extension UIViewController {
    @objc func shouldPopFromNavigation() -> Bool {
        return true
    }
}

在你的视图控制器中,你可以这样处理:

@objc override func shouldPopFromNavigation() -> Bool {
        // Your dialog, example UIAlertViewController or whatever you want
        return false
    }

其他回答

只需control +拖动栏项到func下面。魅力工作

@IBAction func done(sender: AnyObject) {
    if((self.presentingViewController) != nil){
        self.dismiss(animated: false, completion: nil)
        print("done")
    }
}

据我所知,你想清空你的数组,当你按下后退按钮,弹出到你之前的ViewController,让你的数组加载在这个屏幕上

let settingArray  = NSMutableArray()
@IBAction func Back(sender: AnyObject) {
    self. settingArray.removeAllObjects()
    self.dismissViewControllerAnimated(true, completion: nil)
} 
override func willMove(toParent parent: UIViewController?)
{
    super.willMove(toParent: parent)
    if parent == nil
    {
        print("This VC is 'will' be popped. i.e. the back button was pressed.")
    }
}

在我的例子中,viewWillDisappear效果最好。但在某些情况下,必须修改之前的视图控制器。所以这是我的解决方案访问之前的视图控制器,它在Swift 4中工作:

override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        if isMovingFromParentViewController {
            if let viewControllers = self.navigationController?.viewControllers {
                if (viewControllers.count >= 1) {
                    let previousViewController = viewControllers[viewControllers.count-1] as! NameOfDestinationViewController
                    // whatever you want to do
                    previousViewController.callOrModifySomething()
                }
            }
        }
    }

你可以简单地从堆栈中删除不必要的控制器,就像这样:

self.navigationController?.viewControllers.removeAll(where: {
        $0 is FirstViewController || $0 is SecondWithPinController
    })