swift - 调用 setNeedsStatusBarAppearanceUpdate() 后 prefersStatusBarHidden 未更新

Question

我的应用程序中的不同 vc 显示状态栏可见，而其他的则隐藏。这在 info.pList 中设置为 YES

 "View controller-based status bar appearance": YES

 // also tried togging this between yes and no
 "Status bar is initially hidden": YES

该应用程序有 2 个窗口，主窗口和第二个窗口。按下按钮后，第二个窗口会显示在主窗口的前面。第二个窗口的vc隐藏了状态栏。

问题是如果我在显示状态栏的主窗口内的 vc (mainVC) 上，我按下按钮显示第二个窗口，mainVC 的状态栏消失。第二个窗口出现，在我关闭它后，我向 mainVC 发送通知以调用 setNeedsStatusBarAppearanceUpdate() 但是 prefersStatusBarHidden 没有被触发，所以状态栏保持隐藏状态，即使它不应该的。我什至对导航 Controller 进行了子类化，并在其中添加了带有 mainVC 的代码，因为它是根。

为什么 prefersStatusBarHidden 没有被调用？

我在 mainVC 中单独添加了 prefersStatusBarHidden，将 nav 单独添加到 mainVC，然后同时在 mainVC 和它的 nav 中添加。在任何一个地方调用 setNeedsStatusBarAppearanceUpdate() 之后，它仍然没有被调用。

子类导航:

class MainVCNavController: UINavigationController {

    override init(rootViewController: UIViewController) {
        super.init(rootViewController: rootViewController)

        NotificationCenter.default.addObserver(self, selector: #selector(updateStatusBar), name: NSNotification.Name(rawValue: "updateStatusBar"), object: nil)
    }

    let statusBarHidden: Bool = false

    @objc func updateStatusBar() {
        self.setNeedsStatusBarAppearanceUpdate() // this gets called when the notification is triggered
    }

    override var prefersStatusBarHidden: Bool {
        return statusBarHidden // this doesn't get called after setNeedsStatusBarAppearanceUpdate() is called 
    }

    // I added this just to see if it would make a difference but it didn't
    override var preferredStatusBarUpdateAnimation: UIStatusBarAnimation {
        return .slide
    }

    override open var childViewControllerForStatusBarStyle: UIViewController? {
        return self.topViewController
    }

    override open var childViewControllerForStatusBarHidden: UIViewController? {
        return self.topViewController
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
    }
}

MainVC是上面nav的rootVC

class MainVCController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        NotificationCenter.default.addObserver(self, selector: #selector(updateStatusBar), name: NSNotification.Name(rawValue: "updateStatusBar"), object: nil)
    }

    let statusBarHidden: Bool = false

    @objc func updateStatusBar() {
        self.setNeedsStatusBarAppearanceUpdate() // this gets called when the notification is called
    }

    override var prefersStatusBarHidden: Bool {
        return statusBarHidden // this doesn't get called after setNeedsStatusBarAppearanceUpdate() is triggered 
    }

    // I added this just to see if it would make a difference but it didn't
    override var preferredStatusBarUpdateAnimation: UIStatusBarAnimation {
        return .slide
    }
}

第二个窗口中的 SecondVC 隐藏了状态栏。当它被解除时，它会发送通知给上面的 mainVC:

class SecondController: UIViewController {

    override var prefersStatusBarHidden: Bool {
        return true
    }

    if dismissed {
       NotificationCenter.default.post(name: Notification.Name(rawValue: "updateStatusBar"), object: nil)
    }
}

我还读到我需要调用下面的代码来触发 prefersStatusBarHidden 但即使我将这些添加到 updateStatusBar() 也没有什么不同。

navigationController?.setNavigationBarHidden(false, animated: false)
// or
navigationController?.navigationBar.isHidden = false

Answer 1

更新状态栏需要在主线程。

有两种方法可以确保:

在主线程上添加通知观察者:(你不需要将函数暴露给objc c):

NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: "updateStatusBar"), object: nil, queue: .main, using: updateStatusBar)

func updateStatusBar(_ notification: Notification) {
    setNeedsStatusBarAppearanceUpdate()
}

或者在主线程更新状态栏:

NotificationCenter.default.addObserver(self, selector: #selector(updateStatusBar(_:)), name: NSNotification.Name(rawValue: "updateStatusBar"), object: nil)

@objc func updateStatusBar(_ notification: Notification) {

    DispatchQueue.main.sync {
        self.setNeedsStatusBarAppearanceUpdate()
    }
}