Ranging beacons in background - ios

Question

I want to rang beacons in the background. With background i mean when the phone goes to lock screen. I want the app to continue ranging beacons. The problem i have now is that the code never finds beacons. I have two beacons who is working but the AppDelegate don't find them. When i run the same code in a ViewController, it finds the beacons and displays them. How can i do it?
#interface BDAppDelegate () <AXABeaconManagerDelegate>
#end
#implementation BDAppDelegate {
NSMutableDictionary *beaconRegions;
NSMutableDictionary *detectBeacons;
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
return YES;
}
- (void)applicationWillResignActive:(UIApplication *)application {
}
- (void)applicationDidEnterBackground:(UIApplication *)application {
CLBeaconRegion *beaconRegion = [[CLBeaconRegion alloc] initWithProximityUUID:[[NSUUID alloc] initWithUUIDString:#"MyUUID"] identifier:#"微信"];
[AXABeaconManager sharedManager].beaconDelegate = self;
[[AXABeaconManager sharedManager] requestAlwaysAuthorization];
[[AXABeaconManager sharedManager] startRangingBeaconsInRegion:beaconRegion];
self->beaconRegions = [[NSMutableDictionary alloc] init];
self->detectBeacons = [[NSMutableDictionary alloc] init];
while (detectBeacons.count < 10) {
NSLog(#"Rows in detectBeacons %lu", (unsigned long)beaconRegions.count);
}
self->beaconRegions[beaconRegion] = [NSArray array];
}
- (void)didRangeBeacons:(NSArray *)beacons inRegion:(CLBeaconRegion *)region {
self->beaconRegions[region] = beacons;
NSMutableArray *allBeacons = [NSMutableArray array];
for (NSArray *regionResult in [self->beaconRegions allValues])
{
[allBeacons addObjectsFromArray:regionResult];
}
NSPredicate *pre = [NSPredicate predicateWithFormat:#"accuracy != -1"];
NSArray *rights = [allBeacons filteredArrayUsingPredicate:pre];
NSString * str = #"accuracy";
self->detectBeacons[str] = rights;
}
#end

Answer 1

On iOS, apps are limited to ranging for 5 seconds in the background. This timer is restarted each time the app is put to the background, or when a beacon monitoring event (entered region / exited region) fires. The good news is that you can extend the time allowed to range beacons in the background to 3 minutes after each of these events.
I put together a blog post that shows you how to do it here.

Answer 2

For CLLocationManager there is a method startMonitoringForRegion(CLBeaconRegion *):beaconRegion
which should be added before we start startRangingBeaconsInRegion.
So if your AXABeaconManager class is from CLLocationManager add this:
[[AXABeaconManager sharedManager] startMonitoringForRegion:beaconRegion];
Otherwise:
Create a CLLocationManager object locationManager and initialize it then add start monitoring like below.
[self.locationManager startMonitoringForRegion:beaconRegion];
before you startRangingBeaconsInRegion
Discussion: startMonitoringForRegion
You must call this method once for each region you want to monitor. If an existing region with the same identifier is already being monitored by the app, the old region is replaced by the new one. The regions you add using this method are shared by all location manager objects in your app and stored in the monitoredRegions property.
for more refer here

Answer 3

ranging for beacons is an operation that consumes a lot of battery and iOS won't allow you to do it endlessly in the BG (most of the time. there are cases, where it works)
what you gotta do is call iOS your doing BG work:
UIBackgroundTaskIdentifier token = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
NSLog(#"Ranging for region %# killed", region.identifier);
}];
if(token == UIBackgroundTaskInvalid) {
NSLog(#"cant start background task");
}
THEN do whatever
when done, call endBackgroundTask