允许 http 请求 ，ios 9 之后需要添加，便于向服务器发送请求
<key>NSAppTransportSecurity</key>  
 <dict>   
  <key>NSAllowsArbitraryLoads</key>   
  <true/>  
 </dict>

添加定位权限，ios8之后需要添加，否则无法定位
<key>NSLocationWhenInUseUsageDescription</key>
  <string>YES</string>  
<key>NSLocationAlwaysUsageDescription</key>
  <string>YES</string>

#import "ViewController.h"
@interface ViewController ()
@end

@implementation ViewController
- (void)viewDidLoad {     
    [super viewDidLoad];   
    // Do any additional setup after loading the view, typically from a nib.      
    self.view.backgroundColor = [UIColor whiteColor];    
    self.title = @"后台定位";    
    self.locationManager = [[CLLocationManager alloc] init];    
    self.locationManager.delegate = self;      
    [self.locationManager setDesiredAccuracy:kCLLocationAccuracyBest];    
    if ([[UIDevice currentDevice].systemVersion floatValue] > 8)     {
          /** 请求用户权限：分为：只在前台开启定位  /在后台也可定位， */
          /** 只在前台开启定位 */
          //        [self.locationManager requestWhenInUseAuthorization];
          /** 后台也可以定位 */         
          [self.locationManager requestAlwaysAuthorization];     
     }    
     if ([[UIDevice currentDevice].systemVersion floatValue] > 9)     {
          /** iOS9新特性：将允许出现这种场景：同一app中多个location manager：一些只能在前台定位，另一些可在后台定位（并可随时禁止其后台定位）。 */   
          [self.locationManager setAllowsBackgroundLocationUpdates:YES];
     }     
     /** 开始定位 */     
     [self.locationManager startUpdatingLocation]; 
}
#pragma mark -  定位代理方法
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray<CLLocation *> *)locations {    
      CLLocation *loc = [locations objectAtIndex:0];    
      NSLog(@"经纬度  %f  %f ",loc.coordinate.latitude,loc.coordinate.longitude);    
      NSURLSession *session = [NSURLSession sharedSession];   
      NSURLSessionDataTask *task = [session dataTaskWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://ac.ybjk.com/ua.php"]] completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {//        
          ／／NSLog(@"response  %@",response);          
          NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];       
          NSLog(@"result %@",result);     
      }];      
      [task resume]; 
}   
- (void)didReceiveMemoryWarning {     
     [super didReceiveMemoryWarning];    
     // Dispose of any resources that can be recreated.
}
@end