单击时,自定义注释视图图像将恢复为接点

我使用下面的代码在地图上显示自定义图像(而不是默认的pin)。但是,当我点击一个项目(并显示标注)时,图像将恢复为默认的红色pin。即使显示标注,如何保留自定义图像?

- (MKAnnotationView *) mapView:(MKMapView *)map viewForAnnotation:(id <MKAnnotation>)annotation
{
    MKPinAnnotationView *pinAnnotation = nil;

    if (annotation != mapView.userLocation) 
    {
        static NSString *pinID = @"mapPin";
        pinAnnotation = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:pinID];
        if (pinAnnotation == nil)
            pinAnnotation = [[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:pinID] autorelease];

        // Set the image
        pinAnnotation.image = [UIImage imageNamed:@"TestIcon.png"];

        // Set ability to show callout
        pinAnnotation.canShowCallout = YES;

        // Set up the disclosure button on the right side
        UIButton *infoButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
        pinAnnotation.rightCalloutAccessoryView = infoButton;

        [pinID release];
    }

    return pinAnnotation;
    [pinAnnotation release];
}