避免创建多个 ViewController 实例，iOS Swift

问题描述

在 AppDelegate 中，每当收到 VoIP 呼叫(推送通知)时，都会调用以下函数，从而创建多个VideoCallViewController"实例

In AppDelegate, the below function gets called whenever VoIP call (push notification) is received thereby creating multiple instances of "VideoCallViewController"

如下所示，我使用 deinit(在 VideoCallViewController 中)来检查是否在创建新的VideoCallViewController"实例之前取消了先前的VideoCallViewController"实例，令我惊讶的是 print("Deinitializing VC) 未被调用，将实例留在内存中.

I've used deinit (in VideoCallViewController) as shown below, to check if the previous instance of "VideoCallViewController" was being de-initialised before a new instance of "VideoCallViewController" is created, to my surprise print("Deinitializing VC) wasn't called, leaving the instance in memory.

如果 AppDelegate 中已经存在 VideoCallViewController 的实例，我如何显示 VideoCallViewController 及其导航控制器.

How can I show VideoCallViewController with its Navigation Controller if an instance of VideoCallViewController already exists from AppDelegate.

在 VideoCallViewController 中

deinit {
  print("Deinitializing VC)
}

在 AppDelegate 中

func pushRegistry(_ registry: PKPushRegistry, didReceiveIncomingPushWith payload: PKPushPayload, forType type: PKPushType) {

    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    videoVC = storyboard.instantiateViewController(withIdentifier: "VideoCallViewController") as! VideoCallViewController

    self.window = UIWindow(frame: UIScreen.main.bounds)
    self.window?.rootViewController = videoVC
    self.window?.makeKeyAndVisible()

}

推荐答案

可能的解决方案:创建单例持有对可空窗口的引用，负责视频通话流程.在通知更改可见窗口.通话结束 - 返回应用程序主窗口.

Possible solution: Create singleton holding reference to nullable window, responsible for video calls flow. On notification change visible windows. On call end - return to the application main window.

例如:

class VideoCallManager {
    //MARK: - Singleton
    static let sharedInstance = VideoCallManager()
    private init() {}

    private var videoCallWindow: UIWindow?

    func navigateToVideoCallViewController() {
        if let window = self.videoCallWindow, window.keyWindow {
             //VideoCallViewController is displayed at the moment.
             return
        }

        videoCallWindow = UIWindow.init(frame: UIScreen.mainScreen().bounds)
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        videoVC = storyboard.instantiateViewController(withIdentifier: "VideoCallViewController") as! VideoCallViewController

        self.videoCallWindow?.rootViewController = videoVC
        self.videoCallWindow?.makeKeyAndVisible()
    }

    func returnToWindowOfAppDelegate() {
        if let window = self.videoCallWindow, window.keyWindow {
            (UIApplication.sharedApplication().delegate as? AppDelegate)?.window?.makeKeyAndVisible()

            self.videoCallWindow = nil
        }
    }
}

你的方法看起来像:

func pushRegistry(_ registry: PKPushRegistry, didReceiveIncomingPushWith payload: PKPushPayload, forType type: PKPushType) {
    VideoCallManager.sharedInstance.navigateToVideoCallViewController()
}

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