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

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)
    }
}

其他回答

    override public func viewDidLoad() {
         super.viewDidLoad()
         self.navigationController?.navigationBar.topItem?.title = GlobalVariables.selectedMainIconName
         let image = UIImage(named: "back-btn")

         image = image?.imageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal)

        self.navigationItem.leftBarButtonItem = UIBarButtonItem(image: image, style: UIBarButtonItemStyle.Plain, target: self, action: #selector(Current[enter image description here][1]ViewController.back) )
    }

    func back() {
      self.navigationController?.popToViewController( self.navigationController!.viewControllers[ self.navigationController!.viewControllers.count - 2 ], animated: true)
    }

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)
    })}

当返回按钮按下,忽略交互式弹出与屏幕边缘手势。

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    
    if isMovingFromParent, transitionCoordinator?.isInteractive == false {
      // code here
    }
  }

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)
    }
}

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。