MapKit How to pass managedObject from mapView to mapDetailView

问题

I am trying to pass a managedObject from a mapView with multiple annotation to a mapDetailView with only one annotation of the managedObject passed. This works great in a tableView to mapDetaiView. Any help would be appreciated. My code ...

- (void)viewDidLoad {
[super viewDidLoad];

if (self.managedObjectContext == nil) { 
    self.managedObjectContext = [(CrossroadsTreasuresAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
}

// setup the mapView
[mapView removeAnnotations:mapView.annotations];
[mapView setMapType:MKMapTypeStandard];
[mapView setZoomEnabled:YES];
[mapView setScrollEnabled:YES];
[self.view insertSubview:mapView atIndex:0];
[mapView setDelegate:self];

// setup the location coordnates to Victoria, TX
double lat = [@"28.825" doubleValue];
double lng = [@"-97.009" doubleValue];
CLLocationCoordinate2D rcoord;
rcoord.latitude = lat;
rcoord.longitude = lng;

// setup the map region
//MapLocation *annotation = [[MapLocation alloc] init];
MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(rcoord, 25000, 25000);
MKCoordinateRegion adjustRegion = [mapView regionThatFits:region];
[mapView setRegion:adjustRegion animated:YES];

NSError *error;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"GarageSaleItem" inManagedObjectContext:[self managedObjectContext]];
[fetchRequest setEntity:entity];
NSArray *markerObjects = [[self managedObjectContext] executeFetchRequest:fetchRequest error:&error];

for (int i = 0; i < [markerObjects count]; i++) {
    NSDictionary *marker = (NSDictionary *)[markerObjects objectAtIndex:i];

    // Set the annotation coordnates
    double lat = [[marker valueForKey:@"latitude"] doubleValue];
    double lng = [[marker valueForKey:@"longitude"] doubleValue];
    CLLocationCoordinate2D coord;
    coord.longitude = lng;
    coord.latitude = lat;

    // Create the annotation instatnce
    MapLocation *annotation = [[MapLocation alloc] init];

    // Set the annotation display information
    annotation.coordinate = coord;
    annotation.streetAddress = [marker valueForKey:@"streetAddress"];
    annotation.city = [marker valueForKey:@"city"];
    annotation.state = [marker valueForKey:@"state"];
    annotation.zipCode = [marker valueForKey:@"zipCode"];

    // Add the annotation the the map
    [self.mapView addAnnotation:annotation];
    [annotation release];
}
[fetchRequest release];
}


- (MKAnnotationView *)mapView:(MKMapView *)theMapView viewForAnnotation:(id <MKAnnotation>)annotation {
// if it's the user location, just return nil.
if ([annotation isKindOfClass:[MKUserLocation class]])
    return nil;

// handle our two custom annotations
//
if ([annotation isKindOfClass:[MapLocation class]]) {
    // try to dequeue an existing pin view first
    static NSString* AnnotationIdentifier = @"com.coastalbendmedia.pin";
    MKPinAnnotationView* pinView = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:AnnotationIdentifier];
    if (!pinView) {
        // if an existing pin view was not available, create one
        MKPinAnnotationView* customPinView = [[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:AnnotationIdentifier] autorelease];

        customPinView.pinColor = MKPinAnnotationColorPurple;
        customPinView.animatesDrop = YES;
        customPinView.canShowCallout = YES;

        // add a detail disclosure button to the callout which will open a new view controller page
        //
        // note: you can assign a specific call out accessory view, or as MKMapViewDelegate you can implement:
        //  - (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control;
        //
        UIButton* rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
        customPinView.rightCalloutAccessoryView = rightButton;

        return customPinView;
    } else {
        pinView.annotation = annotation;
    }
    return pinView;
}
return nil;
}


- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control; {


DetailViewController *controller = [[DetailViewController alloc] initWithNibName:@"DetailViewController" bundle:nil];

// Pass the selected object to the new view controller.
[self.navigationController pushViewController:controller animated:YES];

// Set the detail item in the detail view controller.
    // THIS IS WHERE MY PROBLEM IS! indexPath Undeclared
NSManagedObject *selectedObject = [[self fetchedResultsController] objectAtIndexPath:indexPath];
controller.detailItem = selectedObject;
[controller release];

}

回答1:

indexPath is undeclared because you're not implementing a UITableViewDataSource method in this case! I don't know what you're trying to accomplish here, but I think that there could be more than one possible solution. First, you could try to add an object property to your annotation, and use that to get the corresponding NSManagedObject from the annotation. Second, you could use an NSMutableDictionary to store the objects instead of an NSArray. You would use it as follows:

NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];

for(NSManagedObject *object in markerObjects) {
  // Create the annotation
  MapLocation *annotation = [[MapLocation alloc] init];

  [dictionary setObject:object forKey:annotation]
}

Then you would retrieve the corresponding object for an annotation like this:

- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control {
  NSManagedObject *object = [dictionary objectForKey:view.annotation];

  // Do whatever you want with your object
}

Please note that MapLocation here must conform to the NSCopying protocol since it is copied by the setObject:forKey: method.

Third, you could add all the informations (address, city, state, etc.) to your NSManagedObject subclass that conforms to the MKAnnotation protocol, and you won't have anymore the problem of retreiving an annotation corresponding to an object, since that would be the same.

来源：https://stackoverflow.com/questions/3256883/mapkit-how-to-pass-managedobject-from-mapview-to-mapdetailview