iphone - distanceFromLocation 似乎不起作用

Question

在应用程序中，我需要计算两点之间的距离。我就是这样做的。

- (void)locationManager:(CLLocationManager *)manager
    didUpdateToLocation:(CLLocation *)newLocation
           fromLocation:(CLLocation *)oldLocation{
    NSLog(@"updating");
     //Getting my concerts
    arrConcerten = [matches mutableCopy];

       for (Event *concert in arrConcerten) {
            CLLocation *restaurnatLoc = [[CLLocation alloc] initWithLatitude:[concert.eve_latitude floatValue] longitude:[concert.eve_longitude floatValue]];

            CLLocationDistance meters = [restaurnatLoc distanceFromLocation:newLocation];
            NSLog(@"meters are %f",meters);
            if(meters > 5000){
                [locationManager2 stopUpdatingLocation];
                NSString *message2 = [NSString stringWithFormat:@"Long = %f and lat= %f and Concert Lat = %f and long = %f",newLocation.coordinate.longitude,newLocation.coordinate.latitude,[concert.eve_latitude floatValue],[concert.eve_longitude floatValue]];
                NSLog(@"%@",message2);
            }else{

                NSLog(@"too far away");
            }

        }
    }

这就是我的日志所说的。

2013-10-17 15:57:23.518 Domino[7468:907] meters are 7973.753294
2013-10-17 15:57:23.520 Domino[7468:907] Long = 5.621456 and lat= 51.097340 and Concert Lat = 51.038139 and long = 5.557330
2013-10-17 15:57:23.896 Domino[7468:907] meters are 27850.874245
2013-10-17 15:57:23.899 Domino[7468:907] Long = 5.621456 and lat= 51.097340 and Concert Lat = 50.860332 and long = 5.493722

如您所见，这些位置彼此靠近。但它仍然说我们距离太远了。有人可以帮助我吗？

Answer 1

你为什么要用这个:

如果超过 5000 米:做点什么，否则太远了？我不明白其中的逻辑。如果距离太远，则超过 5000 米。所以我认为:

  - (void)locationManager:(CLLocationManager *)manager
        didUpdateToLocation:(CLLocation *)newLocation
               fromLocation:(CLLocation *)oldLocation{
        NSLog(@"updating");
         //Getting my concerts
        arrConcerten = [matches mutableCopy];

       for (Event *concert in arrConcerten) {
            CLLocation *restaurnatLoc = [[CLLocation alloc] initWithLatitude:[concert.eve_latitude floatValue] longitude:[concert.eve_longitude floatValue]];

            CLLocationDistance meters = [restaurnatLoc distanceFromLocation:newLocation];
            NSLog(@"meters are %f",meters);
            if(meters <= 5000){
                [locationManager2 stopUpdatingLocation];
                NSString *message2 = [NSString stringWithFormat:@"Long = %f and lat= %f and Concert Lat = %f and long = %f",newLocation.coordinate.longitude,newLocation.coordinate.latitude,[concert.eve_latitude floatValue],[concert.eve_longitude floatValue]];
                NSLog(@"%@",message2);
            }else{

                NSLog(@"too far away");
            }

        }
    }

或科西斯:

if(meters > 5000){

                    NSLog(@"it's far enough");
 }else{

                    NSLog(@"too close");
 }

还有一件非常重要的事情:

This method measures the distance between the two locations by tracing a line between them that follows the curvature of the Earth. The resulting arc is a smooth curve and does not take into account specific altitude changes between the two locations. from apple documentation

distanceFromLocation 测量“空中”的距离，而不是逐个测量。