iphone mkannotationview strange problem - possibly being reused - iphone

Question

I've just found a strange issue with my sub classed mkannotationview.
When I add the first 5 markers, they all work perfectly. In the mkannotationview sub class, I NSLog a message which I see 5 times. However, when I remove ALL the markers and redraw them - using all the same methods, I see the NSLog only once.
It's like the map is reusing existing annotationviews? Is there a way to force it to use new ones each time?
[UPDATE with code]
So the reason I cannot reuse (and this may or may not be the problem) is that I am creating unique markers with a label. The label on the marker contains a reference to the individual marker (consider it like a product ID)
So... in ProductPlot.h
#interface ProductPlot : NSObject <MKAnnotation> {
NSString *productID;
float latitude;
float longitude;
}
#property (nonatomic, copy) NSString *productID;
and ProductPlot.m
#implementation ProductPlot
#synthesize productID;
- (CLLocationCoordinate2D)coordinate {
CLLocationCoordinate2D coord = {self.latitude, self.longitude};
return coord;
}
- (NSString *) productID {
return productID;
}
then I have the annotation view sub classed as ProductPlotView.h
#interface ProductPlotView : MKAnnotationView {
ProductPlot *product;
}
and in ProductPlotView.m
#implementation ProductPlotView
- (id)initWithAnnotation:(id <MKAnnotation>)annotation reuseIdentifier:(NSString *)reuseIdentifier {
if(self = [super initWithAnnotation:annotation reuseIdentifier:reuseIdentifier]) {
product = (ProductPlot *)annotation;
UILabel *plate2 = [[[UILabel alloc] init] autorelease];
plate2.text = product.productID;
plate2.frame = CGRectMake(35, 4, 100, 30);
plate2.backgroundColor = [UIColor clearColor]; //]clearColor];
[plate2 setFont: [UIFont fontWithName: #"myFont" size: plate2.font.pointSize]];
[self addSubview:plate2];
}
self.frame = CGRectMake(0,0,133,40);
return self;
}
So then in my code, I plot the points using
- (void)plotPoint: (int) y latitude: (double) lat longitude: (double) lng productID: (NSString *) pID {
ProductPlot *newAnnotation = [[ProductPlot alloc] init];
newAnnotation.latitude = lat;
newAnnotation.longitude = lng;
newAnnotation.productID = pID;
[mapView addAnnotation:newAnnotation];
[newAnnotation release];
}
I also have the code to handle the annotations.
- (MKAnnotationView *)mapView:(MKMapView *)lmapView viewForAnnotation:(id <MKAnnotation>)annotation {
ProductPlotView *eventView = (ProductPlotView *)[lmapView
dequeueReusableAnnotationViewWithIdentifier:#"eventview"];
if(eventView == nil) {
eventView = [[[VehicleViewInfo alloc] initWithAnnotation:annotation
reuseIdentifier:#"eventview"]
autorelease];
}
eventView.annotation = annotation;
return eventView;
}
So... the above will take the productID and place it on a label which is the map marker. This seems to work perfectly on the FIRST plot instance, but if I remove the markers (using [mapView removeAnnotations:mapView.annotations];) then call this function again, it draws the points OK, but the product IDs are not correct. It appears to draw them at random.
NOTE: the code above has had a few
parts removed, so there may be typos
Thanks for any info.

Answer 1

To answer my own question, I added MKAnnotationView* annotationView = nil; to the top of my - (MKAnnotationView *)mapView:(MKMapView *)lmapView viewForAnnotation:(id <MKAnnotation>)annotation code.
Now it seems to be working perfectly. I'd still be keen to see if others think that this is the correct way to do this?

Answer 2

I solved a similar problem checking subviews on annotation view.
if it hasn't subviews i create a new label and add it as subview, if it has subviews i take the first and edit the label.text property.
In this way subviews are always zero or only one.