Question

您好

我正在尝试在后台执行任务，因为我需要在应用程序运行时从服务器中提取数据。我在AppDelegate.swift中编写代码，这是我写的代码：

    class AppDelegate: UIResponder, UIApplicationDelegate, UISplitViewControllerDelegate {

        var window: UIWindow?
        let manager = AppManager.manager
        var timer: NSTimer? = nil

        func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
            // Override point for customization after application launch.
            self.timer = NSTimer(timeInterval: 1.0, target: self, selector: "UpdateDeviceData:", userInfo: nil, repeats: true)
           return true
         }                                                                                                           
         func UpdateDeviceData(timer:NSTimer) {
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), { () -> Void in
               print("do some background task")

               dispatch_async(dispatch_get_main_queue(), { () -> Void in
                  print("update some UI")

            })
        })
    }

}

我在“print”行中设置了断点，但它从未执行过。

请问可能出现什么问题？

注意：我正在使用Xcode 7 beta和Swift

Answer 1

您需要在运行循环上安排计时器 - 您只需将其分配给变量即可。尝试使用类方法+ scheduledTimerWithTimeInterval:target:selector:userInfo:repeats: -

所以

NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: "UpdateDeviceData:", userInfo: nil, repeats: true)

NSTimer不会在选择器中调用该方法

1 个答案: