Annotation map pin title showing wrongly - ios

Question

Annotation pin title shows same title for all pins. I have set label to show the title of each pin but I am getting same title for all labels. I did NSLog
of lbl.text and in NSLog it shows different title.
Why am I getting same title for all map pins.
-(void)maprequests
{
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
// getting an NSString
NSString *emailid = [prefs stringForKey:#"email"];
NSString *deviceid = [Request UDID];
//NSString * walkGUID=[prefs stringForKey:#"walkguid"];
//NSLog(#"walkGUID:%#",walkGUID);
NSString * walkguid=[prefs stringForKey:#"walkguid"];
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:#"http://10.0.0.28/web/ws/get_poilist_walks.php?strEmailID=%#&strDeviceID=%#&strWalkGuid=%#",emailid,deviceid,walkguid]];
NSLog(#"%#",url);
NSURLRequest *request = [NSURLRequest requestWithURL:url];
//AFNetworking asynchronous url request
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
operation.responseSerializer.acceptableContentTypes = [NSSet setWithObject:#"text/html"];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
self.pointofintrests = [responseObject objectForKey:#"PointOfIntrests"];
NSIndexPath *indexpath;
NSDictionary *tempDictionary= [self.pointofintrests objectAtIndex:indexpath.row];
for (NSDictionary *dictionary in _pointofintrests)
{
MKCoordinateRegion region = { {0.0, 0.0 }, { 0.0, 0.0 } };
NSString * latitude= [dictionary objectForKey:#"Latitude"];
NSString * longitude =[dictionary objectForKey:#"Longitude"];
double strlatitude = [latitude doubleValue];
double strlongitude = [longitude doubleValue];
region.center.latitude =strlatitude;
region.center.longitude = strlongitude;
region.span.longitudeDelta = 0.01f;
region.span.latitudeDelta = 0.01f;
[_mapview setRegion:region animated:YES];
[_mapview setDelegate:self];
DisplayMap *ann = [[DisplayMap alloc] init];
ann.coordinate = region.center;
[_mapview addAnnotation:ann];
}
}
failure:^(AFHTTPRequestOperation *operation, NSError *error)
{
NSLog(#"Request Failed: %#, %#", error, error.userInfo);
}];
[operation start];
}
- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation{
MKPinAnnotationView *pinView = nil;
UILabel *label;
if(annotation != mapView.userLocation)
{
static NSString *defaultPinID = #"com.invasivecode.pin";
pinView = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:defaultPinID];
if ( pinView == nil ) pinView = [[MKPinAnnotationView alloc]
initWithAnnotation:annotation reuseIdentifier:defaultPinID];
if(![annotation isKindOfClass:[DisplayMap class]])
return nil;
DisplayMap *a = (DisplayMap *)annotation;
pinView.image=[UIImage imageNamed:#"push_pin#2x"];
UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(10, 30, 250, 30)];
lbl.backgroundColor = [UIColor clearColor];
lbl.textColor = [UIColor whiteColor];
lbl.alpha = 0.5;
lbl.tag = 42;
for (int i=0; i<_pointofintrests.count; i++)
{
lbl.text = [[_pointofintrests valueForKey:#"title"] objectAtIndex:i];
}
[pinView addSubview:lbl];
[_mapview selectAnnotation:pinView animated:YES];
pinView.canShowCallout = YES;
pinView.animatesDrop = NO;
}
else
{
}
return pinView;
}

Answer 1

Your problem is you are looping over _pointofinterests
for (int i=0; i<_pointofintrests.count; i++)
{
lbl.text = [[_pointofintrests valueForKey:#"title"] objectAtIndex:i];
}
This isn't doing what you think. Its assigning the last title in the array to every pin.
Because the viewForAnnotation delegate method gives you the annotation that will display, I tend to keep an array of annotations to save the index, and therefore you can access your data correctly.
When you call [_mapview addAnnotation:ann]; also save ann into an array.
You should then be able todo something like:
[[_pointofintrests valueForKey:#"title"] objectAtIndex:[annArray indexOfObject:annotation]]
As a side note, if _pointofinterests is an NSDictionary I would use objectForKey instead.

Answer 2

The main reason you are getting the same label text on all pins is, as already pointed out in another answer, that for every pin, lbl.text is always set to the title of the last object in _pointofintrests.
The solution I would prefer however is to set the annotation's title and use that to set the label's text.
When creating the annotation and before calling addAnnotation, set its title property:
DisplayMap *ann = [[DisplayMap alloc] init];
ann.coordinate = region.center;
ann.title = [dictionary objectForKey:#"title"]; //<-- add this line
[_mapview addAnnotation:ann];
In viewForAnnotation, instead of the for loop, you can simply set the label's text to the annotation's title (no searching of arrays or looping):
//for (int i=0; i<_pointofintrests.count; i++)
//{
// lbl.text = [[_pointofintrests valueForKey:#"title"] objectAtIndex:i];
//}
lbl.text = annotation.title;
That technically fixes the problem of the same text appearing on all pins.
However, there are some other issues with the code in viewForAnnotation which will become apparent after the above fix:
The UILabel is being added to the annotation view even if the annotation view was dequeued (meaning a previously created view is being re-used). That dequeued view will already have a UILabel in it and the existing code will add another one on top. After panning and zooming the map for a while, you will notice overlapping labels for each pin.
The UILabel should only be added when a new view is created (when the dequeue returns nil and you alloc+init a new one).
Another problem is that since you are using a custom image for your annotations, you should create a plain MKAnnotationView instead of an MKPinAnnotationView. The MKPinAnnotationView class is designed for showing the standard, built-in pin image and although it still has an image property, it tends to sometimes ignore that and revert to showing its standard pin image.
Another problem is this line:
[_mapview selectAnnotation:pinView animated:YES];
The map view can only have one annotation "selected" at a time so if you were thinking that calling this in viewForAnnotation would show the callout for all the annotations at once, then that is mistaken.
The selectAnnotation method requires the annotation as the first parameter. The pinView is not the annotation -- it is the annotation's view (they are not the same thing). The compiler must be complaining about this line and at run-time, the system is probably showing an error in the console saying something like "Trying to select an annotation which has not been added". So technically, the line should be [_mapview selectAnnotation:annotation animated:YES];
Regardless, do not call selectAnnotation in the viewForAnnotation delegate method. Doing so may lead to recursion and a stack overflow (and an EXC_BAD_ACCESS) because the select causes the annotation's view to be updated which causes viewForAnnotation to be called, etc. Instead, call it in the didAddAnnotationViews delegate method for the one annotation you want to show the callout for.
Your revised viewForAnnotation delegate method might look like this:
-(MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation
{
if(! [annotation isKindOfClass:[DisplayMap class]])
{
return nil;
}
static NSString *defaultPinID = #"MyPin";
int lblTag = 42;
MKAnnotationView *pinView = [mapView dequeueReusableAnnotationViewWithIdentifier:defaultPinID];
if (pinView == nil)
{
pinView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:defaultPinID];
pinView.image = [UIImage imageNamed:#"push_pin#2x"];
pinView.canShowCallout = YES;
//Create and add the label to the view ONCE when creating the view...
UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(10, 30, 250, 30)];
lbl.backgroundColor = [UIColor clearColor];
lbl.textColor = [UIColor whiteColor];
lbl.alpha = 0.5;
lbl.tag = lblTag;
[pinView addSubview:lbl];
}
else
{
//If we are re-using a dequeued view
//update its annotation reference...
//(otherwise view will still be pointing to its previous annotation)
pinView.annotation = annotation;
}
//At this point, we have a new or dequeued view
//pointing to the current annotation.
//Now update the label that will already be there
//with the current annotation's title...
UILabel *lbl = (UILabel *)[pinView viewWithTag:lblTag];
lbl.text = annotation.title;
return pinView;
}
Remember you'll need to set the annotation's title as shown at the top of the answer as well.
There are also some things in the for loop in the maprequests method that I want to point out:
It's not necessary to create and set a region just to set the annotation's coordinate. Calling setRegion in the loop is pointless and inefficient since the user will only end up seeing the map positioned at the last annotation anyway. To set an annotation coordinate, just do:
ann.coordinate = CLLocationCoordinate2DMake(strlatitude, strlongitude);
You can call setRegion (once) after the for loop (or just call [_mapview showAnnotations:_mapview.annotations animated:YES]; so you don't have to yourself calculate the region that shows all the annotations).
You don't need to set the map view's delegate inside the for loop repeatedly. Set the delegate (once) before the for loop (though it should already have been set long before this method is called).