ios - Swift2 iOS Reachability Class 和 NSNotificatonCenter 未接收广播

Question

我有一个带有 2 个选项卡的 tabBarController 和一个用于互联网连接的 Reachability 类。

在 AppDelegate 的 didFinishLaunching 方法中，我有一个 checkReachability 函数，用于检查当前网络连接以查看 wifi 是否打开或关闭在任何一种情况下，它都会向第二个选项卡广播 NSNotification。

在第二个选项卡内有标签，在 viewDidLoad 内有 2 个观察者在监听广播。我还有 2 个函数(由观察者触发)会根据当前网络连接更改标签文本。

我正在使用模拟器，当我从第一个或第二个选项卡打开/关闭 wifi 时，第二个选项卡的标签文本永远不会改变。

为什么文本没有变化，为什么观察者没有反应？

可达性等级:仅供引用，我从这个 youtube 视频中获得了可达性类，并将其从 Swift 3 切换到 Swift 2.3:https://www.youtube.com/watch?v=IlsfXjESatg&t=532s

import Foundation
import UIKit
import SystemConfiguration

protocol Utilities {
}

extension NSObject:Utilities{

    enum ReachabilityStatus {
        case notReachable
        case reachableViaWWAN
        case reachableViaWiFi
    }

    var currentReachabilityStatus: ReachabilityStatus {

        var zeroAddress = sockaddr_in(sin_len: 0, sin_family: 0, sin_port: 0, sin_addr: in_addr(s_addr: 0), sin_zero: (0, 0, 0, 0, 0, 0, 0, 0))

        zeroAddress.sin_len = UInt8(sizeofValue(zeroAddress))
        zeroAddress.sin_family = sa_family_t(AF_INET)

        guard let defaultRouteReachability = withUnsafePointer(&zeroAddress, {
            SCNetworkReachabilityCreateWithAddress(nil, UnsafePointer($0))
        }) else {
            return .notReachable
        }

        var flags: SCNetworkReachabilityFlags = []
        if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
            return .notReachable
        }

        if flags.contains(SCNetworkReachabilityFlags.Reachable) == false{
            // The target host is not reachable.
            return .notReachable
        }
        else if flags.contains(SCNetworkReachabilityFlags.IsWWAN) == true{
            // WWAN connections are OK if the calling application is using the CFNetwork APIs.
            return .reachableViaWWAN
        }

        else if flags.contains(.ConnectionRequired) == false {
            // If the target host is reachable and no connection is required then we'll assume that you're on Wi-Fi...
            return .reachableViaWiFi
        }
        else if (flags.contains(.ConnectionOnDemand) == true || flags.contains(.ConnectionOnTraffic) == true) && flags.contains(.InterventionRequired) == false {
            // The connection is on-demand (or on-traffic) if the calling application is using the CFSocketStream or higher APIs and no [user] intervention is needed
            return .reachableViaWiFi
        }
        else {
            return .notReachable
        }
    }
}

应用委托(delegate):

class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

    self.checkReachability()

    return true
}
//This function is declared inside AppDelegate 
func checkReachability(){
    if currentReachabilityStatus == .reachableViaWiFi {
            NSNotificationCenter.defaultCenter().postNotificationName("wifi", object: nil)
    }else if currentReachabilityStatus == .reachableViaWWAN{
            print("WWAN.")
    }else{
            NSNotificationCenter.defaultCenter().postNotificationName("noWifi", object: nil)
    }
}

第二个标签:

class SecondTabController: UIViewController {

@IBOutlet weak var labelTwo: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()
    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(wifiConnection), name: "wifi", object: nil)

    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(noConnection), name: "noWifi", object: nil)
 }

func wifiConnection(){
    self.labelTwo.text = "Wifi Connection"
 }

func noConnection(){
    self.labelTwo.text = "No Connection"
 }

deinit{
    NSNotificationCenter.defaultCenter().removeObserver(self, name: "wifi", object: nil)
    NSNotificationCenter.defaultCenter().removeObserver(self, name: "noWifi", object: nil)
 }
}

Answer 1

您仅将通知发布到通知中心一次，即在应用程序启动时:

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    // Your method `checkReachability` will post notifications:
    self.checkReachability()
    return true
}

但是您的 SecondTabController 尚未创建，因此尚未订阅接收您在应用程序启动时发送的通知。通知发布后，任何订阅者都会立即收到通知。通知“不要等到”稍后添加某个订阅者。

作为可达性管理器，您可能需要什么，它会在 WiFi 可达性发生变化时继续运行并向通知中心发布通知。

您可能想要使用现有的可达性管理器，such as Alamofire's NetworkReachabilityManager as described in this question .