iOS MapKit - Is it possible to change a map pin based on map type?

Question

I cannot find an exact question to this.

I have some custom pins that look ok on a Standard map. I want to use other pins if the map changes to Satellite or Hybrid.

Is this possible?

I've tried this so far:

    annotationImageName = @"blackPin.png";

    if (segment == 1) {
        NSLog(@"segment 1");
        annotationImageName = @"whitePin.png";
    }
    else if (segment == 2) {
        NSLog(@"segment 2");
        annotationImageName = @"greyPin.png";
    }


}

......

MKAnnotationView *annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"annotationPin"];

annotationView.image = [UIImage imageNamed:annotationImageName];

Answer 1

You can make your own annotation view class that observes a custom notification that you will post when the mapType property of the map view changes:

@interface MyAnnotationView : MKAnnotationView
@property (nonatomic, strong) id<NSObject> observer;
@end

static NSString *kMapTypeChangeNotificationKey = @"com.domain.app.maptypechange";

@implementation MyAnnotationView

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self.observer];
}

- (instancetype)initWithAnnotation:(id<MKAnnotation>)annotation reuseIdentifier:(NSString *)reuseIdentifier mapType:(MKMapType)mapType {
    self = [super initWithAnnotation:annotation reuseIdentifier:reuseIdentifier];

    if (self) {
        [self updateImageBasedUponMapType:mapType];

        typeof(self) __weak weakSelf = self;
        self.observer = [[NSNotificationCenter defaultCenter] addObserverForName:kMapTypeChangeNotificationKey object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification *note) {
            MKMapType mapType = [note.userInfo[@"mapType"] unsignedIntegerValue];
            [weakSelf updateImageBasedUponMapType:mapType];
        }];
    }

    return self;
}

- (void)updateImageBasedUponMapType:(MKMapType)mapType {
    if (mapType == MKMapTypeStandard) {
        self.image = [UIImage imageNamed:@"whitePin.png"];
    } else if (mapType == MKMapTypeSatellite) {
        self.image = [UIImage imageNamed:@"greyPin.png"];
    } else {
        NSLog(@"Unexpected mapType %lu", (unsigned long)mapType);
    }
}

@end

Clearly, this means that when you instantiate it, you have to pass it a reference to the map type:

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation {
    if ([annotation isKindOfClass:[MKUserLocation class]]) { return nil; }

    static NSString *reuseIdentifier = @"MyCustomAnnotation";

    MyAnnotationView *annotationView = (id)[mapView dequeueReusableAnnotationViewWithIdentifier:reuseIdentifier];
    if (annotationView) {
        annotationView.annotation = annotation;
    } else {
        annotationView = [[MyAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:reuseIdentifier mapType:mapView.mapType];
        annotationView.canShowCallout = true;
    }

    return annotationView;
}

Now, when you update the mapType of the map, also post this custom annotation:

- (IBAction)changedValueSegmentControl:(UISegmentedControl *)sender {
    if (sender.selectedSegmentIndex == 0) {
        self.mapView.mapType = MKMapTypeStandard;
    } else if (sender.selectedSegmentIndex == 1) {
        self.mapView.mapType = MKMapTypeSatellite;
    }

    [[NSNotificationCenter defaultCenter] postNotificationName:kMapTypeChangeNotificationKey object:self userInfo:@{@"mapType" : @(self.mapView.mapType)}];
}