ios 定位

Question

用到ios自带的定位，想把当前位置在地图上标记出来，定位位置很准确，但是定位的位置却没有在mapview控件的中央，有哪位碰到过这样得问题吗？
以下是代码

@implementation MyMap001ViewController
{
    MKMapView *mapview;
    CLLocationManager *locationManager;
}

-(void)viewDidLoad
{
    mapview=[[MKMapView alloc]initWithFrame:CGRectMake(0, 0, 320, 460)];
    mapview.showsUserLocation = YES;
    mapview.mapType = MKMapTypeSatellite;
    [self.view addSubview:mapview];
    
    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate = self;
    [locationManager startUpdatingLocation];
}
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {

    [locationManager stopUpdatingLocation];
    NSString *strLat = [NSString stringWithFormat:@"%.4f",newLocation.coordinate.latitude];
    NSString *strLng = [NSString stringWithFormat:@"%.4f",newLocation.coordinate.longitude];
    NSLog(@"Lat: %@  Lng: %@", strLat, strLng);
    
    CLLocationCoordinate2D coords = CLLocationCoordinate2DMake(newLocation.coordinate.latitude,newLocation.coordinate.longitude);
    float zoomLevel = 0.002;
    MKCoordinateRegion region = MKCoordinateRegionMake(coords,MKCoordinateSpanMake(zoomLevel, zoomLevel));
    [mapview setRegion:[mapview regionThatFits:region] animated:YES];
}

Answer 1

本来就不在中点的。
给你个category，你加到工程中，在mapview需要显示CLLocationCoordinate2D的地方调用就行了。

//zoomLevel 1~28
[mapView setCenterCoordinate:CLLocationCoordinate2DMake(lat, lng)
						   zoomLevel:zoomLevel
							animated:YES];

MapViewUtil.h

#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>

@interface MKMapView (MapViewUtil)

- (void)setCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate
                  zoomLevel:(NSUInteger)zoomLevel
                   animated:(BOOL)animated;

@end 

MapViewUtil.m

#import "MapViewUtil.h"

#define MERCATOR_OFFSET 268435456
#define MERCATOR_RADIUS 85445659.44705395

@implementation MKMapView (MapViewUtil)

#pragma mark -
#pragma mark Map conversion methods

- (double)longitudeToPixelSpaceX:(double)longitude
{
    return round(MERCATOR_OFFSET + MERCATOR_RADIUS * longitude * M_PI / 180.0);
}

- (double)latitudeToPixelSpaceY:(double)latitude
{
    return round(MERCATOR_OFFSET - MERCATOR_RADIUS * logf((1 + sinf(latitude * M_PI / 180.0)) / (1 - sinf(latitude * M_PI / 180.0))) / 2.0);
}

- (double)pixelSpaceXToLongitude:(double)pixelX
{
    return ((round(pixelX) - MERCATOR_OFFSET) / MERCATOR_RADIUS) * 180.0 / M_PI;
}

- (double)pixelSpaceYToLatitude:(double)pixelY
{
    return (M_PI / 2.0 - 2.0 * atan(exp((round(pixelY) - MERCATOR_OFFSET) / MERCATOR_RADIUS))) * 180.0 / M_PI;
}

#pragma mark -
#pragma mark Helper methods

- (MKCoordinateSpan)coordinateSpanWithMapView:(MKMapView *)mapView
                             centerCoordinate:(CLLocationCoordinate2D)centerCoordinate
                                 andZoomLevel:(NSUInteger)zoomLevel
{
    // convert center coordiate to pixel space
    double centerPixelX = [self longitudeToPixelSpaceX:centerCoordinate.longitude];
    double centerPixelY = [self latitudeToPixelSpaceY:centerCoordinate.latitude];
    
    // determine the scale value from the zoom level
    NSInteger zoomExponent = 20 - zoomLevel;
    double zoomScale = pow(2, zoomExponent);
    
    // scale the map’s size in pixel space
    CGSize mapSizeInPixels = mapView.bounds.size;
    double scaledMapWidth = mapSizeInPixels.width * zoomScale;
    double scaledMapHeight = mapSizeInPixels.height * zoomScale;
    
    // figure out the position of the top-left pixel
    double topLeftPixelX = centerPixelX - (scaledMapWidth / 2);
    double topLeftPixelY = centerPixelY - (scaledMapHeight / 2);
    
    // find delta between left and right longitudes
    CLLocationDegrees minLng = [self pixelSpaceXToLongitude:topLeftPixelX];
    CLLocationDegrees maxLng = [self pixelSpaceXToLongitude:topLeftPixelX + scaledMapWidth];
    CLLocationDegrees longitudeDelta = maxLng - minLng;
    
    // find delta between top and bottom latitudes
    CLLocationDegrees minLat = [self pixelSpaceYToLatitude:topLeftPixelY];
    CLLocationDegrees maxLat = [self pixelSpaceYToLatitude:topLeftPixelY + scaledMapHeight];
    CLLocationDegrees latitudeDelta = -1 * (maxLat - minLat);
    
    // create and return the lat/lng span
    MKCoordinateSpan span = MKCoordinateSpanMake(latitudeDelta, longitudeDelta);
    return span;
}

#pragma mark -
#pragma mark Public methods

- (void)setCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate
                  zoomLevel:(NSUInteger)zoomLevel
                   animated:(BOOL)animated
{
    // clamp large numbers to 28
    zoomLevel = MIN(zoomLevel, 28);
    
    // use the zoom level to compute the region
    MKCoordinateSpan span = [self coordinateSpanWithMapView:self centerCoordinate:centerCoordinate andZoomLevel:zoomLevel];
    MKCoordinateRegion region = MKCoordinateRegionMake(centerCoordinate, span);
    
    // set the region like normal
    [self setRegion:region animated:animated];
}

@end