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
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
}
}
其他回答
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
}
}
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)
})}
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()
}
}
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。
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
}