User location image pin disappears most of time - iphone

Question

i Am using following code
-(MKAnnotationView *) mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation
{
if ([[annotation title] isEqualToString:#"Current Location"] )
{
MKAnnotationView *anView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:#"currentPin"];
anView.image = [UIImage imageNamed:#"pin_green.png"];
anView.canShowCallout = true;
anView.enabled = true;
return anView;
}
The issue is, it randomly disappears and appears again. Giving a very bad user experience. Any way to fix this?

Answer 1

There are several suspect things about this code:
You're not using dequeue, as someone has pointed out. In particular, the problem here is that you are making a new view every single time, rather than checking to see whether a new view needs making.
You are forgetting the key step, namely, to associate the view with the annotation.
Here is the canonical structure of a simple viewForAnnotation: implementation where we supply our own view:
- (MKAnnotationView *)mapView:(MKMapView *)mapView
viewForAnnotation:(id <MKAnnotation>)annotation {
MKAnnotationView* v = nil;
if ([annotation.title isEqualToString:#"Current Location"]) {
static NSString* ident = #"greenPin";
v = [mapView dequeueReusableAnnotationViewWithIdentifier:ident];
if (v == nil) {
v = [[MKAnnotationView alloc] initWithAnnotation:annotation
reuseIdentifier:ident];
v.image = [UIImage imageNamed:#"pin_green.png"];
v.canShowCallout = YES;
}
v.annotation = annotation;
}
return v;
}
Since that code works for me, I'd suggest you start with it and tweak it as necessary.
By the way, you do NOT need this method just to get a green pin! You do know that, right? iOS will give you a green pin (MKPinAnnotationColorGreen).

Answer 2

You should use MKMapView's dequeueReusableAnnotationViewWithIdentifier: and see if you get a view back before creating a new one with initWithAnnotation:reuseIdentifier::
MKAnnotationView *anView = [mapView dequeueReusableAnnotationViewWithIdentifier:#"currentPin"];
if (!anView) {
anView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:#"currentPin"];
anView.image = [UIImage imageNamed:#"pin_green.png"];
anView.canShowCallout = true;
anView.enabled = true;
}
return anView;
That said, I'm not entirely sure this is the cause of your problem.