Question

I want to design a dynamic pin annotation on Google map in iPhone such that user can drag the pin by taping on it and place this pin on Google maps to set the location of its choice.
After user puts the pin I want to get the location coordinates and location name corresponding to that pin.
Any suggestion how to develop this in iPhone.
Thanks

Answer 1

In your view controller you have to implement methods from MKMapViewDelegate protocol and LongPressGestureAware (which I created) for dropping the pin on the map when the user taps and hold on the screen.

Your annotation should implement MKAnnotation and MKReverseGeocoderDelegate protocols.

I paste some of my code which can help you:

SimpleMapAnnotationViewController.h:

@interface SimpleMapAnnotationViewController : TTViewController<LongPressGestureAware, MKMapViewDelegate> {
    SimpleMapAnnotation *_dropPin;
    MKPinAnnotationView *_pinView;
}

SimpleMapAnnotationViewController.m :

#pragma mark -
#pragma mark LongPressGestureAware

-(void) initLongPressGestureRecognizer {
    UILongPressGestureRecognizer *longPressGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPressGesture:)];
    [self.map addGestureRecognizer:longPressGesture];
    [longPressGesture release];
}

-(void)handleLongPressGesture:(UIGestureRecognizer*)sender {

    if([sender isMemberOfClass:[UILongPressGestureRecognizer class]] && (sender.state == UIGestureRecognizerStateEnded || sender.state == UIGestureRecognizerStateBegan)) {
    [self.map removeGestureRecognizer:sender]; //avoid multiple pins to appear when holding on the screen
    } 
    CGPoint point = [sender locationInView:self.map];
    CLLocationCoordinate2D theCoordinate = [self.map convertPoint:point toCoordinateFromView:self.map];
    self.dropPin = [[[SimpleMapAnnotation alloc] initWithCoordinate:theCoordinate] autorelease];
    [self.map addAnnotation:self.dropPin];
    [self performSelector:@selector(selectInitialAnnotation) withObject:nil afterDelay:0.5];
}

-(void)selectInitialAnnotation {
    [self.map selectAnnotation:[self.map.annotations objectAtIndex:0] animated:YES];
}

#pragma mark -
#pragma mark MKMapViewDelegate

- (MKAnnotationView *) mapView: (MKMapView *) mapView viewForAnnotation: (id<MKAnnotation>) annotation {
    if (annotation == self.map.userLocation){
        return nil; //default to blue dot
    }
    MKPinAnnotationView *pin = (MKPinAnnotationView *) [mapView dequeueReusableAnnotationViewWithIdentifier: @"annotation_ID"];
    if (pin == nil) {
        pin = [[[MKPinAnnotationView alloc] initWithAnnotation: annotation reuseIdentifier: @"annotation_ID"] autorelease];
    } else {
        pin.annotation = annotation;
    }

    pin.canShowCallout = YES;
    pin.draggable = YES;
    pin.animatesDrop = YES;
    pin.pinColor = MKPinAnnotationColorGreen;

    self.pinView = pin;
    self.dropPin.pinView = self.pinView;    
    return pin;
}


- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)annotationView didChangeDragState:(MKAnnotationViewDragState)newState fromOldState:(MKAnnotationViewDragState)oldState {
//NSArray *annotations = self.map.annotations;
if (oldState == MKAnnotationViewDragStateDragging) {
    SimpleMapAnnotation *annotation = (SimpleMapAnnotation *)annotationView.annotation;
    [annotation updateSubtitle];    
}
if(newState == MKAnnotationViewDragStateEnding) {
    NSLog(@"drag finish");
}
}

SimpleMapAnnotation.h

@interface SimpleMapAnnotation : NSObject <MKAnnotation, MKReverseGeocoderDelegate> {
    CLLocationCoordinate2D _coordinate;
    NSString *_title;
    NSString *_subtitle;
    MKPinAnnotationView *_pinView; 
}

SimpleMapAnnotation.m

- (id)initWithCoordinate:(CLLocationCoordinate2D)coordinate {  
    self.coordinate = coordinate;
    MKReverseGeocoder *geoCoder = [[MKReverseGeocoder alloc] initWithCoordinate:self.coordinate];
    geoCoder.delegate = self;
    [geoCoder start];
    self.subtitle = [NSString   stringWithFormat:@"%f %f", self.coordinate.latitude, self.coordinate.longitude]; 
return self;
}

#pragma mark -
#pragma mark MKReverseGeocoderDelegate

// this delegate is called when the reverseGeocoder finds a placemark
- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFindPlacemark:(MKPlacemark *)placemark
{
    MKPlacemark * myPlacemark = placemark;
    NSString *address = [myPlacemark.addressDictionary objectForKey:(NSString*) kABPersonAddressStreetKey];
    self.title = address;
}

// this delegate method is called if an error occurs in locating your current location
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error 
{
    NSLog(@"locationManager:%@ didFailWithError:%@", manager, error);
}

// this delegate is called when the reversegeocoder fails to find a placemark
- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFailWithError:(NSError *)error
{
     //invalid place
}