11

我正在尝试设置地图区域（中心和跨度），以便地图同时显示所有引脚注释。

我在将长/纬度坐标从 NSString 转换为双精度时遇到问题。和他们一起计算。这是我正在使用的代码：

- (void)updateMemberPins{

//calculate new region to show on map
double center_long = 0.0f;
double center_lat = 0.0f;
double max_long = 0.0f;
double min_long = 0.0f;
double max_lat = 0.0f;
double min_lat = 0.0f;

for (Member *member in members) {
    
    //find min and max values
    if ([member.locLat doubleValue] > max_lat) {max_lat = [member.locLat doubleValue];}
    if ([member.locLat doubleValue] < min_lat) {min_lat = [member.locLat doubleValue];}
    if ([member.locLong doubleValue] > max_long) {max_long = [member.locLong doubleValue];}
    if ([member.locLong doubleValue] < min_long) {min_long = [member.locLong doubleValue];}
    
    //sum up long and lang to get average later
    center_lat = center_lat + [member.locLat doubleValue];
    center_long = center_long + [member.locLong doubleValue];
}

//calculate average long / lat
center_lat = center_lat / [members count];
center_long = center_long / [members count];

NSLog(@"center long: %d, center lat: %d", center_long, center_lat);
NSLog(@"max_long: %d, min_long: %d, max_lat: %d, min_lat: %d", max_long, min_long, max_lat, min_lat);
    
//create new region and set map
CLLocationCoordinate2D coord = {latitude: center_lat, longitude: center_long};
MKCoordinateSpan span = MKCoordinateSpanMake(abs(max_lat) + abs(min_lat), abs(max_long) + abs(min_long));
MKCoordinateRegion region = {coord, span};
[resultMapView setRegion:region];

//remove all pins from map
[resultMapView removeAnnotations:resultMapView.annotations];

//show member pins
for (id member in members) {
    [resultMapView addAnnotation:(Member *) member];
}

}

日志输出的结果是：

中长：-1946827116，中纬：1075651472

max_long：-6267216，min_long：1076018553，max_lat：0，min_lat：0

我认为问题来自（错误地）将值从 NSString 转换为 double，但是我找不到让它工作的方法......位置字符串的格式就像'43.5686473'。

有什么提示吗？欢呼

4

4 回答 4

22

对于那些寻找类似东西的人来说，最终的工作代码：

    - (void)updateMemberPins{

    //remove all pins from map
    [resultMapView removeAnnotations:resultMapView.annotations];

    if ([members count] > 0) {

        @try {
            //calculate new region to show on map           
            Member *firstMember = [members objectAtIndex:0];
            double max_long = [firstMember.locLong doubleValue];
            double min_long = [firstMember.locLong doubleValue];
            double max_lat = [firstMember.locLat doubleValue];
            double min_lat = [firstMember.locLat doubleValue];

            //find min and max values
            for (Member *member in members) {
                if ([member.locLat doubleValue] > max_lat) {max_lat = [member.locLat doubleValue];}
                if ([member.locLat doubleValue] < min_lat) {min_lat = [member.locLat doubleValue];}
                if ([member.locLong doubleValue] > max_long) {max_long = [member.locLong doubleValue];}
                if ([member.locLong doubleValue] < min_long) {min_long = [member.locLong doubleValue];}
            }

            //calculate center of map
            double center_long = (max_long + min_long) / 2;
            double center_lat = (max_lat + min_lat) / 2;

            //calculate deltas
            double deltaLat = abs(max_lat - min_lat);
            double deltaLong = abs(max_long - min_long);

            //set minimal delta
            if (deltaLat < 5) {deltaLat = 5;}
            if (deltaLong < 5) {deltaLong = 5;}

            //debug
            //NSLog(@"center long: %f, center lat: %f", center_long, center_lat);
            //NSLog(@"max_long: %f, min_long: %f, max_lat: %f, min_lat: %f", max_long, min_long, max_lat, min_lat);

            //create new region and set map
            CLLocationCoordinate2D coord = {latitude: center_lat, longitude: center_long};
            MKCoordinateSpan span = MKCoordinateSpanMake(deltaLat, deltaLong);
            MKCoordinateRegion region = {coord, span};
            [resultMapView setRegion:region];


        }
        @catch (NSException * e) {
            NSLog(@"Error calculating new map region: %@", e);
        }
        @finally {
            //show member pins
            for (id member in members) {
                [resultMapView addAnnotation:(Member *) member];
            }
        }



    }

}
于 2011-02-21T08:09:07.420 回答
5

要在 NSLog() 中显示双精度值，您应该使用%f, 而不是%d ChangeNSLog()部分，如下所示：

NSLog(@"center long: %f, center lat: %f", center_long, center_lat);
NSLog(@"max_long: %f, min_long: %f, max_lat: %f, min_lat: %f", max_long, min_long, max_lat, min_lat);

此外，使用 region fromMKMapView比制作自己的要简单得多。一旦设置了缩放比例，您所需要的就是以不同的坐标在地图上动态移动。

MKCoordinateRegion region = self.mapView.region;
region.center = centerCoordinate;
region.span.longitudeDelta /= ratioZoomMax; // Bigger the value, closer the map view
region.span.latitudeDelta /= ratioZoomMax;
[self.mapView setRegion:region animated:YES]; // Choose if you want animate or not
于 2011-02-18T12:06:30.610 回答
2 
//show member pins
        for (id member in members) {
            [resultMapView addAnnotation:(Member *) member];
        }

这可以替换为

[resultMapView addAnnotations:members];
于 2012-10-03T21:28:10.637 回答
0

您可以简单地使用这种代码和平：

-(void)updateMemberPins
{
    if([members count] == 0)
        return;

    double minLat = 90;
    double minLon = 180;
    double maxLat = -90;
    double maxLon = -180;

    for(Member *member in members)
    {
        minLat = fmin(minLat, [member.locLat doubleValue]);
        minLon = fmin(minLon, [member.locLong doubleValue]);
        maxLat = fmax(maxLat, [member.locLat doubleValue]);
        maxLon = fmax(maxLon, [member.locLong doubleValue]);
    }

    NSLog(@"MAX LAT: %f, MIN LAT: %f, MAX LONG: %f, MIN LONG: %f,", maxLat, minLat, maxLon, minLon);

    double midLat =  (minLat + maxLat)/2;
    double midLong = (minLon + maxLon)/2;

    double deltaLat = abs(maxLat - minLat);
    double deltaLong = abs(maxLon - minLon);

    if (deltaLat < 5) {deltaLat = 5;}
    if (deltaLong < 5) {deltaLong = 5;}

    //...
}
于 2013-11-26T09:24:26.943 回答