How to move MKMapView based on selected annotation

问题:

I have an MKMapView which populates the entirety of my view, but when a pin is selected, I am sliding up another view on top of the map. I want to move the map so the pin will appear in the centre of the visible area of the map.

Difficult to explain but hopefully it makes sense! Thanks in advance.

回答1:

You could try getting the MKMapRect from visibleMapRect for the map view, converting the annotation's coordinate to an MKMapPoint, resetting the MKMapRect's origin so the MKMapPoint is in the appropriate position, and then using setVisibleMapRect:animated: to set the visible region to the new MKMapRect.

For example, if you wanted to move the map so the annotation is centered horizontally and 25% of the way down vertically, you could do something like this:

MKMapRect r = [mapView visibleMapRect];
MKMapPoint pt = MKMapPointForCoordinate([annotation coordinate]);
r.origin.x = pt.x - r.size.width * 0.5;
r.origin.y = pt.y - r.size.height * 0.25;
[mapView setVisibleMapRect:r animated:YES]; 

回答2:

Using MKMapViewDelegate method:

func mapView(_ mapView: MKMapView, didSelect view: MKAnnotationView) {

    // center the mapView on the selected pin
    let region = MKCoordinateRegion(center: view.annotation!.coordinate, span: mapView.region.span)
    mapView.setRegion(region, animated: true)
}

回答3:

I ended up with following procedures:

** Centering on annotation:**

- (void) centerOnSelection:(id<MKAnnotation>)annotation
{
    MKCoordinateRegion region = self.mapView.region;
    region.center = annotation.coordinate;

    CGFloat per = ([self sizeOfBottom] - [self sizeOfTop]) / (2 * self.mapView.frame.size.height);
    region.center.latitude -= self.mapView.region.span.latitudeDelta * per;

    [self.mapView setRegion:region animated:YES];
}

** Zooming on annotation:**

- (void) zoomAndCenterOnSelection:(id<MKAnnotation>)annotation
{
    DLog(@"zoomAndCenterOnSelection");

    MKCoordinateRegion region = self.mapView.region;
    MKCoordinateSpan span = MKCoordinateSpanMake(0.005, 0.005);

    region.center = annotation.coordinate;

    CGFloat per = ([self sizeOfBottom] - [self sizeOfTop]) / (2 * self.mapView.frame.size.height);
    region.center.latitude -= self.mapView.region.span.latitudeDelta * span.latitudeDelta / region.span.latitudeDelta * per;

    region.span = span;

    [self.mapView setRegion:region animated:YES];
}

-(CGFloat) sizeOfBottom and -(CGFloat) sizeOfTop both return height of panels covering the mapview from the layout guides