I'm trying to do the union between two MKCoordinateRegion. Does anybody have an idea on how to do this?
问题:
回答1:
There is a MKMapRectUnion
function which accepts two MKMapRects
so you could first convert each MKCoordinateRegion
to an MKMapRect
and then call that function (and convert the result back to an MKCoordinateRegion
using the MKCoordinateRegionForMapRect
function).
The conversion method might look like this:
- (MKMapRect)mapRectForCoordinateRegion:(MKCoordinateRegion)coordinateRegion
{
CLLocationCoordinate2D topLeftCoordinate =
CLLocationCoordinate2DMake(coordinateRegion.center.latitude
+ (coordinateRegion.span.latitudeDelta/2.0),
coordinateRegion.center.longitude
- (coordinateRegion.span.longitudeDelta/2.0));
MKMapPoint topLeftMapPoint = MKMapPointForCoordinate(topLeftCoordinate);
CLLocationCoordinate2D bottomRightCoordinate =
CLLocationCoordinate2DMake(coordinateRegion.center.latitude
- (coordinateRegion.span.latitudeDelta/2.0),
coordinateRegion.center.longitude
+ (coordinateRegion.span.longitudeDelta/2.0));
MKMapPoint bottomRightMapPoint = MKMapPointForCoordinate(bottomRightCoordinate);
MKMapRect mapRect = MKMapRectMake(topLeftMapPoint.x,
topLeftMapPoint.y,
fabs(bottomRightMapPoint.x-topLeftMapPoint.x),
fabs(bottomRightMapPoint.y-topLeftMapPoint.y));
return mapRect;
}
Then, to actually do the union:
MKCoordinateRegion region1 = ...
MKCoordinateRegion region2 = ...
MKMapRect mapRect1 = [self mapRectForCoordinateRegion:region1];
MKMapRect mapRect2 = [self mapRectForCoordinateRegion:region2];
MKMapRect mapRectUnion = MKMapRectUnion(mapRect1, mapRect2);
MKCoordinateRegion regionUnion = MKCoordinateRegionForMapRect(mapRectUnion);
回答2:
If anyone is looking for a swift equivalent using extensions,
extension MKCoordinateRegion {
func mapRectForCoordinateRegion() -> MKMapRect {
let dLat = span.latitudeDelta / 2.0
let dLon = span.longitudeDelta / 2.0
let topLeft = MKMapPointForCoordinate(
CLLocationCoordinate2DMake(center.latitude + dLat, center.longitude - dLon))
let botRight = MKMapPointForCoordinate(
CLLocationCoordinate2DMake(center.latitude - dLat, center.longitude + dLon))
return MKMapRectMake(
topLeft.x,
topLeft.y,
fabs(botRight.x - topLeft.x),
fabs(botRight.y - topLeft.y))
}
func unionWith(region: MKCoordinateRegion) -> MKCoordinateRegion {
let union = MKMapRectUnion(
self.mapRectForCoordinateRegion(),
region.mapRectForCoordinateRegion())
return MKCoordinateRegionForMapRect(union)
}
}
And can be used like
let region1 = ...
let region2 = ...
let regionUnion = region1.unionWith(region2)
回答3:
i did a little test on both 4.3 and 5.0 and it seems that the conversion is not correct
UIImageView *imageView = [[UIImageView alloc] initWithImage:[[UIImage imageNamed:@"heart.png"] imageByScalingProportionallyToSize:CGSizeMake(100, 100)]];
imageView.frame = CGRectMake(0, 0, 100, 100);
imageView.center = [mapView convertCoordinate:mapView.centerCoordinate toPointToView:canvasView];
[canvasView addSubview:imageView];
MKCoordinateRegion region = [mapView convertRect:imageView.frame toRegionFromView:canvasView];
MKMapRect maprect;
for (int i = 0; i < 5; i ++)
{
maprect = [mapView mapRectForCoordinateRegion:region];
NSLog(@"%f, %f, %f, %f", region.center.latitude, region.center.longitude, region.span.latitudeDelta, region.span.longitudeDelta);
NSLog(@"%f, %f, %f, %f", maprect.origin.x, maprect.origin.y, maprect.size.width, maprect.size.height);
region = MKCoordinateRegionForMapRect([mapView mapRectForCoordinateRegion:region]);
}
14.718256, -40.078125, 63.837150, 70.312500
78118912.000000, 94811514.406252, 52428800.000000, 52428799.999997
17.416993, -40.078125, 63.837150, 70.312500
78118912.000000, 91803983.982924, 52428800.000000, 53344239.567355
20.649080, -40.078125, 63.837150, 70.312500
78118912.000000, 87976363.978412, 52428800.000000, 54699220.734715
24.548345, -40.078125, 63.837150, 70.312500
78118912.000000, 82962597.189840, 52428800.000000, 56765991.576236
29.305644, -40.078125, 63.837150, 70.312500
78118912.000000, 76093086.024249, 52428800.000000, 60073659.997575