我在mapView上有一个用户位置(蓝点)和注释.选择注释时,我将文本设置为distLabel – “距离点％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]];
}
我知道有一个函数didUpdateToLocation,但是如何将它与didSelectAnnotationView一起使用？
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation
{
//Did update to location
}
解决方法
地图视图具有selectedAnnotations属性,您可以在didUpdateToLocation方法中使用该属性来指示要从哪个注释获取距离.
(顺便说一句,如果您正在使用地图视图的userLocation,您可能希望使用地图视图的didUpdateUserLocation委托方法而不是使用CLUocationManager委托方法的didUpdateToLocation.)
在委托方法中,您可以检查是否有任何当前选定的注释,如果是,则显示该注释的距离(否则说“未选择注释”).
您可能希望编写一个可以从didSelectAnnotationView和didUpdateUserLocation调用的公共方法,以减少代码重复.
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];
}
