Avendo Segnaposto / annotazione nel centro della vostra MapView, anche se si scorre
-
27-10-2019 - |
Domanda
Ho trascorso molte ore cercando di capire come fare questo:
Avere un segnaposto / annotazione nei centerCoordinate del vostro MapView, quando si scorre la mappa, il segnaposto deve sempre soggiorni in centro.
ho visto un altro app fare anche questo!
Soluzione
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;
}