7

我有一个用户位置（蓝点）和注释mapView。选择注释时，我将文本设置为distLabel- “到点的距离 %4.0f m.”。用户移动时如何更新该文本标签？

didSelectAnnotationView：

- (void)mapView:(MKMapView *)mapView didSelectAnnotationView:(MKAnnotationView *)view
{

    CLLocation *pinLocation = 
      [[CLLocation alloc] initWithLatitude:
                        [(MyAnnotation*)[view annotation] coordinate].latitude 
                                 longitude:
                        [(MyAnnotation*)[view annotation] coordinate].longitude];
    CLLocation *userLocation = 
      [[CLLocation alloc] initWithLatitude:
                          self.mapView.userLocation.coordinate.latitude             
                                 longitude:
                                 self.mapView.userLocation.coordinate.longitude];        
    CLLocationDistance distance = [pinLocation distanceFromLocation:userLocation];

    [distLabel setText: [NSString stringWithFormat:@"Distance to point %4.0f m.",    
                                                     distance]];
}

我知道有一个功能didUpdateToLocation，但我该如何使用它didSelectAnnotationView呢？

- (void)locationManager:(CLLocationManager *)manager
    didUpdateToLocation:(CLLocation *)newLocation
           fromLocation:(CLLocation *)oldLocation
{
  //Did update to location
}
4

1 回答 1

15

地图视图有一个selectedAnnotations属性，您可以在didUpdateToLocation方法中使用该属性来告诉从哪个注释获取距离。

（顺便说一句，如果您使用的是地图视图userLocation，您可能希望使用地图视图的didUpdateUserLocation委托方法，而不是didUpdateToLocation委托CLLocationManager方法。）

在委托方法中，您可以检查当前是否有任何选定的注释，如果有，则显示到该注释的距离（否则说“未选择注释”）。

您可能希望编写一个可以从两者调用的通用方法didSelectAnnotationView并didUpdateUserLocation减少代码重复。

例如：

-(void)updateDistanceToAnnotation:(id<MKAnnotation>)annotation
{
    if (annotation == nil) 
    {
        distLabel.text = @"No annotation selected";
        return;
    }

    if (mapView.userLocation.location == nil) 
    {
        distLabel.text = @"User location is unknown";
        return;
    }

    CLLocation *pinLocation = [[CLLocation alloc] 
        initWithLatitude:annotation.coordinate.latitude
               longitude:annotation.coordinate.longitude];

    CLLocation *userLocation = [[CLLocation alloc] 
        initWithLatitude:mapView.userLocation.coordinate.latitude 
               longitude:mapView.userLocation.coordinate.longitude];

    CLLocationDistance distance = [pinLocation distanceFromLocation:userLocation];

    [distLabel setText: [NSString stringWithFormat:@"Distance to point %4.0f m.", distance]];
}

-(void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation
{
    if (mapView.selectedAnnotations.count == 0)
        //no annotation is currently selected
        [self updateDistanceToAnnotation:nil];
    else
        //first object in array is currently selected annotation
        [self updateDistanceToAnnotation:[mapView.selectedAnnotations objectAtIndex:0]];
}

- (void)mapView:(MKMapView *)mapView didSelectAnnotationView:(MKAnnotationView *)view
{    
    [self updateDistanceToAnnotation:view.annotation];
}
于 2012-06-04T12:55:24.263 回答