AirLocate/APLCalibrationCalculator.m
/* |
File: APLCalibrationCalculator.m |
Abstract: Illustrates how to calibrate the measured power of a beacon. |
Version: 1.1 |
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*/ |
#import "APLCalibrationCalculator.h" |
#import "APLDefaults.h" |
@import CoreLocation; |
static const NSTimeInterval ALCalibrationDwell = 20.0f; |
NSString *AppErrorDomain = @"com.example.apple-samplecode.AirLocate"; |
@interface APLCalibrationCalculator() |
@property CLLocationManager *locationManager; |
@property CLBeaconRegion *region; |
@property (getter=isCalibrating) BOOL calibrating; |
@property NSMutableArray *rangedBeacons; |
@property NSTimer *timer; |
@property (strong) APLCalibrationProgressHandler progressHandler; |
@property (strong) APLCalibrationCompletionHandler completionHandler; |
@property float percentComplete; |
@end |
@implementation APLCalibrationCalculator |
- (id)initWithRegion:(CLBeaconRegion *)region completionHandler:(APLCalibrationCompletionHandler)handler |
{ |
self = [super init]; |
if(self) |
{ |
// This location manager will be used to collect RSSI samples from the targeted beacon. |
_locationManager = [[CLLocationManager alloc] init]; |
_locationManager.delegate = self; |
_region = region; |
_completionHandler = [handler copy]; |
_rangedBeacons = [[NSMutableArray alloc] init]; |
} |
return self; |
} |
- (void)locationManager:(CLLocationManager *)manager didRangeBeacons:(NSArray *)beacons inRegion:(CLBeaconRegion *)region |
{ |
// CoreLocation will call this delegate method at 1 Hz with updated range information. |
@synchronized(self) |
{ |
[_rangedBeacons addObject:beacons]; |
if(_progressHandler) |
{ |
dispatch_async(dispatch_get_main_queue(), ^{ |
// Bump the progress callback back to the UI thread as we'll be updating the UI. |
_percentComplete += 1.0f / ALCalibrationDwell; |
_progressHandler(_percentComplete); |
}); |
} |
} |
} |
- (void)performCalibrationWithProgressHandler:(APLCalibrationProgressHandler)handler |
{ |
@synchronized(self) |
{ |
if(!self.calibrating) |
{ |
// Calibration consists of collecting RSSI samples for 20 seconds. |
// Once we have all the samples we will average the mid-80th percentile in timerElapsed:. |
self.calibrating = YES; |
[self.rangedBeacons removeAllObjects]; |
self.percentComplete = 0.0f; |
self.progressHandler = [handler copy]; |
[self.locationManager startRangingBeaconsInRegion:self.region]; |
self.timer = [[NSTimer alloc] initWithFireDate:[NSDate dateWithTimeIntervalSinceNow:ALCalibrationDwell] interval:0 target:self selector:@selector(timerElapsed:) userInfo:nil repeats:NO]; |
[[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSDefaultRunLoopMode]; |
} |
else |
{ |
// Send back an error if calibration is already in progress. |
NSString *localizedErrorString = NSLocalizedString(@"Calibration is already in progress", @"Error string"); |
NSDictionary *userInfo = @{ NSLocalizedDescriptionKey : localizedErrorString }; |
NSError *error = [NSError errorWithDomain:AppErrorDomain code:4 userInfo:userInfo]; |
dispatch_async(dispatch_get_main_queue(), ^{ |
_completionHandler(0, error); |
}); |
} |
} |
} |
- (void)cancelCalibration |
{ |
@synchronized(self) |
{ |
// Fire the timer early if calibration is being cancelled. |
// timerElapsed: will handle reporting the cancellation. |
if(self.calibrating) |
{ |
self.calibrating = NO; |
[self.timer fire]; |
} |
} |
} |
- (void)timerElapsed:(id)sender |
{ |
@synchronized(self) |
{ |
// We can stop ranging at this point as we've either been cancelled or |
// collected all of the RSSI samples we need. |
[_locationManager stopRangingBeaconsInRegion:_region]; |
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ |
@synchronized(self) { |
__block NSError *error = nil; |
NSMutableArray *allBeacons = [[NSMutableArray alloc] init]; |
NSInteger measuredPower = 0; |
if(!self.calibrating) |
{ |
NSString *localizedErrorString = NSLocalizedString(@"Calibration was cancelled", @"Error string"); |
NSDictionary *userInfo = @{ NSLocalizedDescriptionKey : localizedErrorString }; |
error = [NSError errorWithDomain:AppErrorDomain code:2 userInfo:userInfo]; |
} |
else |
{ |
[self.rangedBeacons enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { |
NSArray *beacons = (NSArray *)obj; |
if(beacons.count > 1) |
{ |
NSString *localizedErrorString = NSLocalizedString(@"More than one beacon of the specified type was found", @"Error string"); |
NSDictionary *userInfo = @{ NSLocalizedDescriptionKey : localizedErrorString }; |
error = [NSError errorWithDomain:AppErrorDomain code:1 userInfo:userInfo]; |
*stop = YES; |
} |
else |
{ |
[allBeacons addObjectsFromArray:beacons]; |
} |
}]; |
if(allBeacons.count <= 0) |
{ |
NSString *localizedErrorString = NSLocalizedString(@"No beacon of the specified type was found", @"Error string"); |
NSDictionary *userInfo = @{ NSLocalizedDescriptionKey : localizedErrorString }; |
error = [NSError errorWithDomain:AppErrorDomain code:3 userInfo:userInfo]; |
} |
else |
{ |
// Measured power is an average of the mid-80th percentile of RSSI samples. |
NSUInteger outlierPadding = allBeacons.count * 0.1f; |
[allBeacons sortUsingDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"rssi" ascending:YES]]]; |
NSArray *sample = [allBeacons subarrayWithRange:NSMakeRange(outlierPadding, allBeacons.count - (outlierPadding * 2))]; |
measuredPower = [[sample valueForKeyPath:@"@avg.rssi"] integerValue]; |
} |
} |
// Bump the completion callback to the UI thread as we'll be updating the UI. |
dispatch_async(dispatch_get_main_queue(), ^{ |
_completionHandler(measuredPower, error); |
}); |
self.calibrating = NO; |
[self.rangedBeacons removeAllObjects]; |
self.progressHandler = nil; |
} |
}); |
} |
} |
@end |
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