Question

使用下面的代码，当位置移动时，我会得到多个红色地标。请看下面的图片。

我想删除旧的地标，并在当前位置使用新地标进行更新。因此，在任何给定时间，只会有一个红色地标。

- (void)locationManager:(CLLocationManager *)aManager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    CLLocationCoordinate2D regionCenter = newLocation.coordinate;
    MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(regionCenter, 400, 400);
    [mapView setRegion:region animated:TRUE];

    [self reverseGeocode:newLocation];
}

-(void)reverseGeocode:(CLLocation *)location
{
    if (!geocoder)
    geocoder = [[CLGeocoder alloc] init];
    [geocoder reverseGeocodeLocation:location completionHandler:^(NSArray* placemarks, NSError* error){
    if (nil != error) {
        UIAlertView *alert =
        [[UIAlertView alloc]
         initWithTitle:NSLocalizedString(@"Error translating coordinates into location",
                                         @"Error translating coordinates into location")
         message:NSLocalizedString(@"Geocoder did not recognize coordinates",
                                   @"Geocoder did not recognize coordinates")
         delegate:self
         cancelButtonTitle:NSLocalizedString(@"OK", @"OK")
         otherButtonTitles:nil];
        [alert show];
    }
    else if ([placemarks count] > 0) {

        placemark = [placemarks objectAtIndex:0];

        MapLocation *annotation = [[MapLocation alloc]init];
        annotation.street = placemark.thoroughfare;
        annotation.city = placemark.locality;
        annotation.state = placemark.administrativeArea;
        annotation.zip = placemark.postalCode;
        annotation.coordinate = location.coordinate;
        [self.mapView addAnnotation:annotation];
    }
  }];
}

enter image description here

Answer 1

在添加其他注释之前，请删除之前的注释

//remove all previous annotations
NSArray *previousAnnotations = self.mapView.annotations;
[self.mapView removeAnnotations: previousAnnotations];

//then add your new annotation here
placemark = [placemarks objectAtIndex:0];
MapLocation *annotation = [[MapLocation alloc]init];
annotation.street = placemark.thoroughfare;
annotation.city = placemark.locality;
annotation.state = placemark.administrativeArea;
annotation.zip = placemark.postalCode;
annotation.coordinate = location.coordinate;
[self.mapView addAnnotation:annotation];

removeAnnotations:

的相关Apple文档链接

如果您只想删除以前的注释，请将其存储为属性，并通过调用removeAnnotation:

将其删除

在@interface声明一个这样的属性：

@property (nonatomic, strong) MapLocation *previousAnnotation;

然后在你的代码中：

//remove the previous annotation if it exists
[self.mapView removeAnnotation: self.previousAnnotation];

//then add your new annotation here
placemark = [placemarks objectAtIndex:0];
MapLocation *annotation = [[MapLocation alloc]init];
annotation.street = placemark.thoroughfare;
annotation.city = placemark.locality;
annotation.state = placemark.administrativeArea;
annotation.zip = placemark.postalCode;
annotation.coordinate = location.coordinate;
[self.mapView addAnnotation:annotation];

//set your property
self.previousAnnotation = annotation;

Answer 2

您可以将注释存储为属性：

标头文件.h或@interface中的

：

@property (nonatomic, strong) MapLocation *myAnnotation;

然后通过调用：

更新它

[myAnnotation setCoordinate:location.coordinate];
[myAnnotation setStreet:placemark.thoroughfare];
[myAnnotation setCity:placemark.locality];
...

Apple文档：MKAnnotation/setCoordinate

iOS MapKit：稍微调整的代码重构

2 个答案: