无论应用程序状态如何，调用延迟 15 秒的方法 [英] Call a method with delay of 15 sec irrespective of app state

问题描述

我需要每 15 秒调用一次方法，不管它是否在 foreground 中的任何视图控制器上，无论它在 background 中还是在killed，我需要随时调用它.

I need to call a method in every 15 seconds irrespective of any fact, whether it is on any view controller in foreground, whether it is in background or it is killed, I need to call it at all times.

我知道我可以使用 NSTimer

NSTimer* myTimer = [NSTimer scheduledTimerWithTimeInterval: 15.0 target: self
                               selector: @selector(callAfterFifteenSeconds:) userInfo: nil repeats: YES];

但是，我想知道在哪里实施它，以便它可以满足我的条件.我想我可以在 App Delegate 中使用它，但我需要一个指导来正确实现它.

But, I wanted to know where to implement it so that it could fulfil my condition. I guess I can use it in App Delegate but I need a guidance for this to implement it correctly.

推荐答案

-如果应用程序被杀死，您将无能为力.

-If the app is killed, you cannot do anything.

-当应用程序在后台时，操作系统可能会在一定时间间隔(我相信是 15 秒)后终止该进程.

-When the app is in background, the OS may kill that process after certain time interval (I believe it is 15 seconds).

虽然您可以在应用程序处于后台时注册位置更改.在这种情况下，您的应用将继续接收位置更新(例如谷歌地图).

Though you can register for location changes, while the app is in background. In that case, your app will continue to receive location updates (such as for google maps).

-(void)callAfterFifteenSeconds {

    //1.) do your work


    //2.) If required, you can also choose to skip the next scheduling.
    BOOL shouldSchedule = YES;

    if (shouldSchedule) {
        //3.)
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(15 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            //
            [self callAfterFifteenSeconds];

        });
    }

}

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