Count while in background (NSTimer for more than 3 mins)

问题

Is there any way to run NSTimer for more than 3 mins in background? I have to create simple app that uses

 `locationManager(manager: CLLocationManager, didRangeBeacons beacons: [CLBeacon], inRegion region: CLBeaconRegion)`

for scan my beacons. I have run into problem when I needed to check if user is exactly 10 seconds near closest beacon. I created

    var timer: NSTimer?
    var lastClosestBeacon: CLBeacon? {
        didSet {
            timer?.invalidate()
            timer = NSTimer.scheduledTimerWithTimeInterval(10, target: self, selector: "showLocalNotification", userInfo: nil, repeats: false)
//            NSRunLoop.mainRunLoop().addTimer(timer!, forMode: NSDefaultRunLoopMode)
        }
    }

When closest beacon changes lastClosestBeacon is set and timer is scheduled. It is working in App and for 3 mins when user enters background(locks phone etc.) with help from Scheduled NSTimer when app is in background? Is there any possibility to check that for more than 3 mins ?

PS. I have already added Background Modes with location updates.

回答1:

You can do it by following way:

1) First include required background mode keys into your Info.plist

2) Check and add following line of code for adding background working of location manager in iOS 9 (update: also works in iOS 10):

if ([self.locationManager respondsToSelector:@selector(setAllowsBackgroundLocationUpdates:)]) {
    [self.locationManager setAllowsBackgroundLocationUpdates:YES];
    [self.locationManager pausesLocationUpdatesAutomatically:NO];
}

3)Then create a new timer with repeated continuously with every 1 sec.

4)In that timer method add these two line of code.

[self.locationManager stopUpdatingLocation];
[self.locationManager startUpdatingLocation];

This make your app run in background more than 3 mins. To be aware, the battery usage may be costly.

回答2:

As of iOS 9, apps are allowed a maximum of 180 seconds (3 minutes) of background execution time upon request. This can be extended indefinitely if you put location updates in the “Required background modes” in your Info.plist. I have verified that doing so lets the background execution run forever. Having this in your Info.plist, however, will require you to get approval from Apple for this background mode before putting your app in the App Store.

If you don't want to request location background mode, there are some other tricks you can do to get around Apple's restrictions, which you can read about here: https://gooddevbaddev.wordpress.com/2013/10/22/ios-7-running-location-based-apps-in-the-background/

A word of caution about using those tricks, though -- they are subject to change in any iOS upgrade, and using them might get your app rejected by reviewers.

来源：https://stackoverflow.com/questions/35313020/count-while-in-background-nstimer-for-more-than-3-mins