处理来自视图控制器的远程通知

Question

我正在尝试处理来自特定视图控制器的远程通知。我已经设置了我的应用程序，因此当我推送远程通知时，某个视图控制器会在 ImageView 中显示特定图像，但是如果不再次推送相同的控制器，我就无法更改图像。一旦呈现视图控制器，我正在尝试从另一个远程通知更改 ImageView 的图像。我实现这一点的想法是创建一种方法来从刚刚呈现的视图控制器的文件中处理远程通知，因此远程通知可以编辑 ImageView 的图像。这就是我在 AppDelegate 中呈现视图控制器的方式：

func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
    if let data = userInfo["showiMac"] as? [String: String], let iMacConfig = data["iMacConfig"] {
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let rootTabBarController = self.window?.rootViewController as! UITabBarController
        let firstNavigationController = storyboard.instantiateViewController(withIdentifier: "initialVC1") as! UINavigationController
        rootTabBarController.viewControllers![0] = firstNavigationController

        //the viewController to present
        let viewController = storyboard.instantiateViewController(withIdentifier: "configureiMac") as! ConfigureiMacViewController

        // present VC
        firstNavigationController.pushViewController(viewController, animated: true, completion: {
            viewController.image = UIImage(named: "iMac" + iMacConfig)
        })

        completionHandler(.noData)


    }
}

这是在我的视图控制器中声明图像的方式：

var image: UIImage! 

override func viewDidLoad() {
     super.viewDidLoad()
     imageView.image = image 
}

Answer 1

在您的应用委托中，执行以下操作：

  weak var configureiMacViewController: ConfigureiMacViewController?

创建帮助函数以保持您的代码简洁易读：

private func updateiMacImage(_ image: UIImage, in existingViewController: ConfigureiMacViewController) {
    existingViewController.image = image
}

private func showiMacImage(_ image: UIImage) {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let rootTabBarController = self.window?.rootViewController as! UITabBarController
    let firstNavigationController = storyboard.instantiateViewController(withIdentifier: "initialVC1") as! UINavigationController
    rootTabBarController.viewControllers![0] = firstNavigationController

    //the viewController to present
    let viewController = storyboard.instantiateViewController(withIdentifier: "configureiMac") as! ConfigureiMacViewController
    configureiMacViewController = viewController

    // present VC
    firstNavigationController.pushViewController(viewController, animated: true, completion: {
        viewController.image = UIImage(named: "iMac" + iMacConfig)
    })
}  

然后更新：

func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
    if let data = userInfo["showiMac"] as? [String: String], let iMacConfig = data["iMacConfig"] {
        let image = UIImage(named: "iMac" + iMacConfig)
        if let existingViewController = configureiMacViewController {
           updateiMacImage(image, in: existingViewController)
        } else {
           showiMacImage(image)
        }    
        completionHandler(.noData)
    }
}

AppDelegate 中的弱变量将存储对视图控制器的引用，但“弱”关键字将允许视图控制器在被解除时从内存中释放，在这种情况下，下次你的变量将为零尝试访问它。如果视图控制器仍然可见，那么它的值仍然会被定义，并且您将能够重新使用它来更新图像。

您很可能还必须将您的 ConfigureiMacViewController 代码更新为：

var image: UIImage! {
    didSet {
        imageView.image = image
    }
}

override func viewDidLoad() {
     super.viewDidLoad()
     imageView.image = image 
}

这确保如果视图控制器已经加载并显示，但您更新了图像变量，则图像视图会加载最新的图像。

祝你好运！