在iOS中呈现锁定屏幕的最佳方法是什么？

Question

I wondering the best way to present lock screen in iOS(swift).

ex) If the user presses the home button or receives a call, I want to display the lock screen when user re-enter the app.

So, I tried this way.

func applicationWillResignActive(_ application: UIApplication) {
    guard let passcodeManageView = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "passcodeManageView") as? PasscodeManageViewController else { return }

    if let window = self.window, let rootViewController = window.rootViewController {
        var currentController = rootViewController
        while let presentController = currentController.presentedViewController {
            currentController = presentController
        }
        currentController.present(passcodeManageView, animated: true, completion: nil)
    }
}

Actually it works pretty well.

However, if the alert window is displayed, it does not work normally.

How can I fixed it? (Sorry for my eng.)

Answer 1

Alert views are always an issue in these cases. A quick solution might be to check if alert view is presented and dismiss it. I played with the following:

    func showOverlayController(currentController: UIViewController) {
    currentController.present(OverlayViewController(), animated: true, completion: nil)
}

if let window = UIApplication.shared.keyWindow, let rootViewController = window.rootViewController {
    var currentController = rootViewController
    while let presentController = currentController.presentedViewController {
        guard presentController as? UIAlertController == nil else {
            presentController.dismiss(animated: false) {
                showOverlayController(currentController: currentController)
            }
            return
        }
        currentController = presentController
    }
    showOverlayController(currentController: currentController)
}

Putting aside animations and all this still seems very bad because I suspect if if a view controller inside navigation controller or tab bar controller (or any other type of content view controller) would present an alert view this issue would again show itself. You could use the same logic of finding a top controller to always present alert view on top controller to overcome this.

So I moved to another way which is I would rather change the root view controller instead of presenting an overlay. So I tried the following:

static var currentOverlay: (overlay: OverlayViewController, stashedController: UIViewController)?
static func showOverlay() {
    guard currentOverlay == nil else { return }
    guard let currentController = UIApplication.shared.keyWindow?.rootViewController else { return }

    let overlay: (overlay: OverlayViewController, stashedController: UIViewController) = (overlay: OverlayViewController(), stashedController: currentController)
    self.currentOverlay = overlay

    UIApplication.shared.keyWindow?.rootViewController = overlay.overlay
}
static func hideOverlay() {
    guard let currentOverlay = currentOverlay else { return }
    self.currentOverlay = nil
    UIApplication.shared.keyWindow?.rootViewController = currentOverlay.stashedController
}

It works great... Until alert view is shown again. So after a bit of an inspection I found out that in case of alert views your application has multiple windows. It makes sense an alert would create a new window over the current one but I am unsure how did anyone think it would be intuitive or that it would in any possible way make sense that you are presenting alert view. I would then expect something like UIApplication.shared.showAlert(alert) but let's put this stupidity aside.

The only real solution I see here is to add a new window for your dialog. To do that you could look around the web. What seems to work for me is the following:

static var currentOverlayWindow: (overlay: OverlayViewController, window: UIWindow, previousWindow: UIWindow)?
static func showOverlay() {
    guard currentOverlay == nil else { return }
    guard let currentWindow = UIApplication.shared.keyWindow else { return }

    let overlay: (overlay: OverlayViewController, window: UIWindow, previousWindow: UIWindow) = (overlay: OverlayViewController(), window: UIWindow(frame: currentWindow.bounds), previousWindow: currentWindow)
    self.currentOverlayWindow = overlay

    overlay.window.backgroundColor = UIColor.black
    overlay.window.rootViewController = overlay.overlay
    overlay.window.windowLevel = UIWindowLevelAlert + 1
    overlay.window.makeKeyAndVisible()

}
static func hideOverlay() {
    guard let currentOverlayWindow = currentOverlayWindow else { return }
    self.currentOverlay = nil
    currentOverlayWindow.window.isHidden = true
    currentOverlayWindow.previousWindow.makeKeyAndVisible()
}

Just to fill in the gaps. What I used as an overlay view controller:

class OverlayViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        let button = UIButton(frame: CGRect(x: 12.0, y: 100.0, width: 150.0, height: 55.0))
        button.setTitle("Dismiss", for: .normal)
        view.addSubview(button)
        button.addTarget(self, action: #selector(onButton), for: .touchUpInside)
    }
    @objc private func onButton() {
        AppDelegate.hideOverlay()
//        self.dismiss(animated: true, completion: nil)
    }

}