iphone - 如何在 IOS 中为 CLLocationManager 设置半径

Question

我有要求，当用户从该点穿过半径时，我必须向用户显示警报视图。如何设置半径。？

Answer 1

首先，您需要使用以下命令创建区域：

CLLocationDegrees latitude = <YOUR_LATITUDE>;
CLLocationDegrees longitude = <YOUR_LONGITUDE>;

CLLocationCoordinate2D center = CLLocationCoordinate2DMake(latitude, longitude);

CLLocationDistance radius = GEO_FENCE_RADIUS;

CLRegion *region = [[CLRegion alloc]initCircularRegionWithCenter:center radius:radius identifier:title];

接下来，您必须通过以下方式监视该区域：

 [locationManager startMonitoringForRegion:region];

然后您可以通过以下委托方法跟踪用户何时进入或退出：

- (void)locationManager:(CLLocationManager *)manager
         didEnterRegion:(CLRegion *)region  {

      //Show your alert as they are entered the region

}
- (void)locationManager:(CLLocationManager *)manager
          didExitRegion:(CLRegion *)region  {
    //Show your alert as they are exited the region

}

- (void)locationManager:(CLLocationManager *)manager
didStartMonitoringForRegion:(CLRegion *)region  {


}

- (void)locationManager:(CLLocationManager *)manager
monitoringDidFailForRegion:(CLRegion *)region
              withError:(NSError *)error    {


}