ios - 修改另一个 View Controller 的对象

Question

我想知道是否可以从 AppDelegate.swift 更改或修改一个对象，例如另一个 View Controller 的按钮。 这是我尝试开始但不知何故卡住了。

func application(_ application: UIApplication,didReceiveRemoteNotification userInfo: [AnyHashable : Any],fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {

   if application.applicationState == .active {
        if self.window?.rootViewController is homeViewController {
            //modify a button exist in homeViewController


        }
   }

}

感谢任何帮助。提前致谢。

Answer 1

您可以使用 NotificationCenter 发送和接收内部通知(注意它们不同于本地和远程通知)。

首先创建你的通知做这样的事情:

extension Notification.Name {
    static let remoteNotificationReceived = Notification.Name("uk.co.company.app.remoteNotificationReceived")
}

然后在要响应的 View Controller 中执行如下操作:

class TestViewController: UIViewController {
    var remoteNotificationReceivedObserver: NSObjectProtocol?

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        remoteNotificationReceivedObserver = NotificationCenter.default.addObserver(forName: Notification.Name.remoteNotificationReceived, object: nil, queue: nil, using: { (notification) in
            DispatchQueue.main.async { // because the notification won't be received on the main queue and you want to update the UI which must be done on the main queue.
                // Put the code to change the button here
            }
        })
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)

        if let remoteNotificationReceivedObserver = remoteNotificationReceivedObserver {
            NotificationCenter.default.removeObserver(remoteNotificationReceivedObserver)
        }
    }
}

然后在您应用的其他地方，您可以像这样发布通知:

    NotificationCenter.default.post(name: Notification.Name.remoteNotificationReceived, object: nil)