iOS : Why can't I get mapkit to display a custom annotation pin image?

问题

figured that using my own custom pin image for annotations would be super easy.

But I have never been able to get it to work, and I have no idea why!

I am simply using:

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

    NSString *annotationIdentifier = @"CustomViewAnnotation";
    CustomAnnotationView * customAnnotationView = (CustomAnnotationView *) [self.mapview dequeueReusableAnnotationViewWithIdentifier:annotationIdentifier];
    if(!customAnnotationView)
    {
        customAnnotationView=[[CustomAnnotationView alloc] initWithAnnotationWithImage:annotation
                                                                       reuseIdentifier:annotationIdentifier 
                                                                   annotationViewImage:[UIImage imageNamed:@"map_location_pin.png"]];
    }

    customAnnotationView.image=[UIImage imageNamed:@"map_location_pin.png"];

    customAnnotationView.canShowCallout= YES;

    return customAnnotationView;
}

I assumed that this should work, as a UIImage is what it is wanting, and I do have the .png file in my project.

It never uses my image, but just the standard red pin. What am I doing wrong here?

回答1:

A couple of thoughts:

Did you define your delegate for your MKMapView? Have you put a breakpoint or NSLog in here to make sure your viewForAnnotation is getting called?

You haven't shared your CustomAnnotationView interface/implementation details, but you don't need to subclass MKAnnotationView unless you're doing something special in there. If you're just replacing the image, you can just do:

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

    NSString *annotationIdentifier = @"CustomViewAnnotation";
    MKAnnotationView* annotationView = [mapview dequeueReusableAnnotationViewWithIdentifier:annotationIdentifier];

    if (annotationView) {
        annotationView.annotation = annotation;
    } else {
        annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:annotationIdentifier];
    }

    annotationView.image = [UIImage imageNamed:@"map_location_pin.png"];
    annotationView.canShowCallout= YES;

    return annotationView;
}

Clearly, though, if you're doing something interesting (like custom annotation when a pin is dragged or dropped), then go ahead and have your CustomAnnotationView subclass MKAnnotationView. It just depends upon what you're trying to do.

Unrelated to your original question, I'd suggest:

that your viewForAnnotation method just use the local mapView variable rather than referencing a class property, self.mapView (though they're undoubtedly the same),

that you contemplate renaming your custom init method. So instead of:

customAnnotationView = [[CustomAnnotationView alloc] initWithAnnotationWithImage:annotation
                                                                 reuseIdentifier:annotationIdentifier 
                                                             annotationViewImage:[UIImage imageNamed:@"map_location_pin.png"]];

that you'd do something like:

customAnnotationView = [[CustomAnnotationView alloc] initWithAnnotation:annotation
                                                        reuseIdentifier:annotationIdentifier 
                                                                  image:[UIImage imageNamed:@"map_location_pin.png"]];

If you're still having troubles, share some of your CustomAnnotationView code with us.

回答2:

I think It's support to you.can you try this code.and you can add my annotation .h and .m files and do some changes My annotataion

my annotation.h

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

    @interface MyAnnotation : NSObject<MKAnnotation> {

        CLLocationCoordinate2D  coordinate;
        NSString*               title;
        NSString*               subtitle;
        UIImage*                image;
    }

    @property (nonatomic, assign)   CLLocationCoordinate2D  coordinate;
    @property (nonatomic, copy)     NSString*               title;
    @property (nonatomic, copy)     NSString*               subtitle;
    @property (nonatomic, retain)       UIImage*                image;

    @end


my annotation.m


        #import "MyAnnotation.h"


    @implementation MyAnnotation

    @synthesize title;
    @synthesize subtitle;
    @synthesize coordinate;
    @synthesize image;
    - (void)dealloc 
    {
        [super dealloc];
        self.title = nil;
        self.subtitle = nil;
        self.image=nil;
    }
    @end





       - (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation

    {

        //NSLog(@"welcome into the map view annotation");

        // if it's the user location, just return nil.

        if ([annotation isKindOfClass:[MKUserLocation class]])

            return nil;

        // try to dequeue an existing pin view first
        static NSString* AnnotationIdentifier = @"AnnotationIdentifier";

        MKPinAnnotationView* pinView = [[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:AnnotationIdentifier]autorelease];

        //annotation.image = [UIImage imageNamed:@"shop-1.png"];

        //[pinView setImage:[UIImage imageNamed:@"shop-1.png"]];

        UIImageView *thumbnailImageView = [[UIImageView alloc] initWithImage:((MyAnnotation *)annotation).image];
        CGRect newBounds = CGRectMake(0.0, 0.0, 32.0, 32.0);
        [thumbnailImageView setBounds:newBounds];
        pinView.leftCalloutAccessoryView = thumbnailImageView;
        [thumbnailImageView release];

        //UIImageView *profileIconView = [[UIImageView alloc] initWithImage:featuredDealcouponImage1];
        // [pinView setImage:featuredDealcouponImage1];
        pinView.animatesDrop=NO;

        pinView.canShowCallout=YES;

        pinView.pinColor=MKPinAnnotationColorGreen;

        UIButton* rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];

        [rightButton setTitle:annotation.title forState:UIControlStateNormal];

        [rightButton addTarget:self action:@selector(_annotation_btn_click:) forControlEvents:UIControlEventTouchUpInside];

        pinView.rightCalloutAccessoryView = rightButton;




        return pinView;

    }