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
一种选择是实现您自己的自定义后退按钮。你需要添加以下代码到你的viewDidLoad方法:
- (void) viewDidLoad {
[super viewDidLoad];
self.navigationItem.hidesBackButton = YES;
UIBarButtonItem *newBackButton = [[UIBarButtonItem alloc] initWithTitle:@"Back" style:UIBarButtonItemStyleBordered target:self action:@selector(back:)];
self.navigationItem.leftBarButtonItem = newBackButton;
}
- (void) back:(UIBarButtonItem *)sender {
// Perform your custom actions
// ...
// Go back to the previous ViewController
[self.navigationController popViewControllerAnimated:YES];
}
更新:
以下是Swift的版本:
override func viewDidLoad {
super.viewDidLoad()
self.navigationItem.hidesBackButton = true
let newBackButton = UIBarButtonItem(title: "Back", style: UIBarButtonItemStyle.Bordered, target: self, action: "back:")
self.navigationItem.leftBarButtonItem = newBackButton
}
@objc func back(sender: UIBarButtonItem) {
// Perform your custom actions
// ...
// Go back to the previous ViewController
self.navigationController?.popViewControllerAnimated(true)
}
更新2:
以下是Swift 3的版本:
override func viewDidLoad {
super.viewDidLoad()
self.navigationItem.hidesBackButton = true
let newBackButton = UIBarButtonItem(title: "Back", style: UIBarButtonItemStyle.plain, target: self, action: #selector(YourViewController.back(sender:)))
self.navigationItem.leftBarButtonItem = newBackButton
}
@objc func back(sender: UIBarButtonItem) {
// Perform your custom actions
// ...
// Go back to the previous ViewController
_ = navigationController?.popViewController(animated: true)
}
其他回答
一种选择是实现您自己的自定义后退按钮。你需要添加以下代码到你的viewDidLoad方法:
- (void) viewDidLoad {
[super viewDidLoad];
self.navigationItem.hidesBackButton = YES;
UIBarButtonItem *newBackButton = [[UIBarButtonItem alloc] initWithTitle:@"Back" style:UIBarButtonItemStyleBordered target:self action:@selector(back:)];
self.navigationItem.leftBarButtonItem = newBackButton;
}
- (void) back:(UIBarButtonItem *)sender {
// Perform your custom actions
// ...
// Go back to the previous ViewController
[self.navigationController popViewControllerAnimated:YES];
}
更新:
以下是Swift的版本:
override func viewDidLoad {
super.viewDidLoad()
self.navigationItem.hidesBackButton = true
let newBackButton = UIBarButtonItem(title: "Back", style: UIBarButtonItemStyle.Bordered, target: self, action: "back:")
self.navigationItem.leftBarButtonItem = newBackButton
}
@objc func back(sender: UIBarButtonItem) {
// Perform your custom actions
// ...
// Go back to the previous ViewController
self.navigationController?.popViewControllerAnimated(true)
}
更新2:
以下是Swift 3的版本:
override func viewDidLoad {
super.viewDidLoad()
self.navigationItem.hidesBackButton = true
let newBackButton = UIBarButtonItem(title: "Back", style: UIBarButtonItemStyle.plain, target: self, action: #selector(YourViewController.back(sender:)))
self.navigationItem.leftBarButtonItem = newBackButton
}
@objc func back(sender: UIBarButtonItem) {
// Perform your custom actions
// ...
// Go back to the previous ViewController
_ = navigationController?.popViewController(animated: true)
}
你可以子类化UINavigationController并重写popViewController(animated: Bool)。除了能够在那里执行一些代码,你还可以防止用户完全返回,例如提示保存或丢弃他当前的工作。
示例实现,其中您可以设置popHandler,由推送的控制器设置/清除。
class NavigationController: UINavigationController
{
var popHandler: (() -> Bool)?
override func popViewController(animated: Bool) -> UIViewController?
{
guard self.popHandler?() != false else
{
return nil
}
self.popHandler = nil
return super.popViewController(animated: animated)
}
}
以及来自跟踪未保存工作的推送控制器的示例使用情况。
let hasUnsavedWork: Bool = // ...
(self.navigationController as! NavigationController).popHandler = hasUnsavedWork ?
{
// Prompt saving work here with an alert
return false // Prevent pop until as user choses to save or discard
} : nil // No unsaved work, we clear popHandler to let it pop normally
作为一个很好的触摸,这也将被interactivePopGestureRecognizer调用,当用户试图返回使用滑动手势。
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)
}
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()
}
}
}
}
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)
})}
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