MapView annotations/pins in iPhone - iphone

Question

In my viewDidLoad: method I have set the MapView like this so that if user has selected all the locations then it should show all the locations/pin views and if only one then only one pin view should be shown.
- (void)viewDidLoad{
[mapView setMapType:MKMapTypeStandard];
[mapView setZoomEnabled:YES];
[mapView setScrollEnabled:YES];
if ([vehicleLabel.text isEqualToString:#"All Vehicles"]) {
MKCoordinateRegion region = {{0.0, 0.0},{0.0, 0.0}};
region.center.latitude = 41.01860;
region.center.longitude = 28.96470;
region.span.longitudeDelta = 0.01f;
region.span.latitudeDelta = 0.01f;
[mapView setRegion:region animated:YES];
[mapView setDelegate:self];
Annotations *ann = [[Annotations alloc] init];
ann.title = #"Vehicle A";
ann.subtitle = #"VG 1";
ann.coordinate = region.center;
[mapView addAnnotation:ann];
NSMutableArray* annotations=[[NSMutableArray alloc] init];
CLLocationCoordinate2D theCoordinate1;
theCoordinate1.latitude = 41.01760;
theCoordinate1.longitude = 30.96470;
CLLocationCoordinate2D theCoordinate2;
theCoordinate2.latitude = 41.01860;
theCoordinate2.longitude = 31.96470;
CLLocationCoordinate2D theCoordinate3;
theCoordinate3.latitude = 41.01360;
theCoordinate3.longitude = 25.96470;
CLLocationCoordinate2D theCoordinate4;
theCoordinate4.latitude = 41.01560;
theCoordinate4.longitude = 27.96470;
Annotations* myAnnotation1=[[Annotations alloc] init];
myAnnotation1.coordinate=theCoordinate1;
myAnnotation1.title=#"Vehicle B";
myAnnotation1.subtitle=#"Group 1";
Annotations* myAnnotation2=[[Annotations alloc] init];
myAnnotation2.coordinate=theCoordinate2;
myAnnotation2.title=#"Vehicle C";
myAnnotation2.subtitle=#"Group 1";
Annotations* myAnnotation3=[[Annotations alloc] init];
myAnnotation3.coordinate=theCoordinate3;
myAnnotation3.title=#"Vehicle D";
myAnnotation3.subtitle=#"Group 1";
Annotations* myAnnotation4=[[Annotations alloc] init];
myAnnotation4.coordinate=theCoordinate4;
myAnnotation4.title=#"Vehicle E";
myAnnotation4.subtitle=#" Group 1";
[mapView addAnnotation:myAnnotation1];
[mapView addAnnotation:myAnnotation2];
[mapView addAnnotation:myAnnotation3];
[mapView addAnnotation:myAnnotation4];
[annotations addObject:myAnnotation1];
[annotations addObject:myAnnotation2];
[annotations addObject:myAnnotation3];
[annotations addObject:myAnnotation4];
NSLog(#"Annotations: %d",[annotations count]);
}
else {
MKCoordinateRegion region = {{0.0, 0.0},{0.0, 0.0}};
region.center.latitude = 41.01860;
region.center.longitude = 28.96470;
region.span.longitudeDelta = 0.01f;
region.span.latitudeDelta = 0.01f;
[mapView setRegion:region animated:YES];
[mapView setDelegate:self];
Annotations *ann = [[Annotations alloc] init];
ann.title = #"Vehicle A";
ann.subtitle = #"VG 1";
ann.coordinate = region.center;
[mapView addAnnotation:ann];
}}
- (MKAnnotationView *)mapView:(MKMapView *)mV viewForAnnotation:(id <MKAnnotation>)annotation{
MKPinAnnotationView *pinView = nil;
if(annotation != mapView.userLocation)
{
static NSString *defaultPinID = #"aPin";
pinView = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:defaultPinID];
if ( pinView == nil )
pinView = [[[MKPinAnnotationView alloc]
initWithAnnotation:annotation reuseIdentifier:defaultPinID] autorelease];
} else {
}
pinView.pinColor = MKPinAnnotationColorRed;
pinView.canShowCallout = YES;
pinView.animatesDrop = YES;
return pinView;}
And in my PickerView didSelectRow method: I have implemented:
-(void)pickerView:(UIPickerView *)pickerViewG didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
if (component == kGroupComponent) {
NSString *selectedState = [self.vehicleGroup objectAtIndex:row];
NSArray *array = [groupVehicles objectForKey:selectedState];
self.vehiclesList = array;
[vehiclePicker selectRow:0 inComponent:kListComponent animated:YES];
[vehiclePicker reloadComponent:kListComponent];
}
NSInteger groupRow = [vehiclePicker selectedRowInComponent:kGroupComponent];
NSInteger vehicleRow = [vehiclePicker selectedRowInComponent:kListComponent];
NSString *group = [self.groupOfVehicles objectAtIndex:groupRow];
NSString *vehicle = [self.listVehicles objectAtIndex:vehicleRow];
groupLabel.text = [[NSString alloc] initWithFormat: #"%#", group];
vehicleLabel.text = [[NSString alloc] initWithFormat: #"%#", vehicle];
valueForOtherView = vehicleLabel.text;}
Here what I want to know is that what if user selects a single vehicle from the picker view then all other pin views/ locations should be hidden/removed from the view and the only selected location/ pin view should be shown.
How can I do that in this picker view didSelectRow method: ?

Answer 1

What I'm doing in a case similar to yours, is:
1) remove first all the annotations
for (id <MKAnnotation> anAnnotation in [NSArray arrayWithArray:mapView_.annotations]) {
[mapView_ removeAnnotation:anAnnotation];
}
2) and then paint the ones selected:
[mapView_ addAnnotation:myAnnotation];