Having Placemark/Annotation in the center of your mapView, even if you scroll - android-mapview

Question

I've spent many hours trying to figure how to do this:
Having a placemark/annotation in the centerCoordinate of your mapView, when you scroll the map, the placemark should always stays in the center.
I've seen another app doing this too!

Answer 1

Found my question in How to add annotation on center of map view in iPhone?
There's the answer :
If you want to use an actual annotation instead of just a regular view positioned above the center of the map view, you can:
use an annotation class with a settable coordinate property (pre-defined MKPointAnnotation class eg). This avoids having to remove and add the annotation when the center changes.
create the annotation in viewDidLoad
keep a reference to it in a property, say centerAnnotation
update its coordinate (and title, etc) in the map view's regionDidChangeAnimated delegate method (make sure map view's delegate property is set)
Example:
#interface SomeViewController : UIViewController <MKMapViewDelegate> {
MKPointAnnotation *centerAnnotation;
}
#property (nonatomic, retain) MKPointAnnotation *centerAnnotation;
#end
#implementation SomeViewController
#synthesize centerAnnotation;
- (void)viewDidLoad {
[super viewDidLoad];
MKPointAnnotation *pa = [[MKPointAnnotation alloc] init];
pa.coordinate = mapView.centerCoordinate;
pa.title = #"Map Center";
pa.subtitle = [NSString stringWithFormat:#"%f, %f", pa.coordinate.latitude, pa.coordinate.longitude];
[mapView addAnnotation:pa];
self.centerAnnotation = pa;
[pa release];
}
- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
centerAnnotation.coordinate = mapView.centerCoordinate;
centerAnnotation.subtitle = [NSString stringWithFormat:#"%f, %f", centerAnnotation.coordinate.latitude, centerAnnotation.coordinate.longitude];
}
- (void)dealloc {
[centerAnnotation release];
[super dealloc];
}
#end
Now this will move the annotation but not smoothly. If you need the annotation to move more smoothly, you can add a UIPanGestureRecognizer and UIPinchGestureRecognizer to the map view and also update the annotation in the gesture handler:
// (Also add UIGestureRecognizerDelegate to the interface.)
// In viewDidLoad:
UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(handleGesture:)];
panGesture.delegate = self;
[mapView addGestureRecognizer:panGesture];
[panGesture release];
UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:#selector(handleGesture:)];
pinchGesture.delegate = self;
[mapView addGestureRecognizer:pinchGesture];
[pinchGesture release];
- (void)handleGesture:(UIGestureRecognizer *)gestureRecognizer
{
centerAnnotation.coordinate = mapView.centerCoordinate;
centerAnnotation.subtitle = [NSString stringWithFormat:#"%f, %f", centerAnnotation.coordinate.latitude, centerAnnotation.coordinate.longitude];
}
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
//let the map view's and our gesture recognizers work at the same time...
return YES;
}