问题
(Using iOS 5 and Xcode 4.2)
I have an MKMapView and want to draw a circle of 1000m radius around the user location.
On the surface it would seem that implementing the mapView:viewForAnnotation: map view delegate method, and adding a custom MKAnnotationView for the users location, would be a perfect solution. It would look something like this:
- (MKAnnotationView *)mapView:(MKMapView *)mapView
viewForAnnotation:(id <MKAnnotation>)annotation
{
// If it's the user location, return my custom MKAnnotationView.
if ([annotation isKindOfClass:[MKUserLocation class]]) {
return myCustomAnnotationView;
} else {
return nil;
}
}
However annotations on the map don't scale when you zoom in and out of the map.
So I tried adding an overlay (because overlays scale with the map), using the MKCircle class and setting its co-ordinates to the latest co-ordinates from my locationManger/map view delegate. However as the coordinate property of MKCircle is readonly, I'm having to remove the overlay then add a new one each time the user moves. Causing a noticeable flicker as it happens.
Is there any way to make an annotation scale seamlessly as the map view is scaled in and out? Or is there a good way to make an overlay move seamlessly with changes in the users location?
I would be very grateful for your help :)
回答1:
Try a custom overlay. Add this in viewDidLoad:
MKCircle *circle = [MKCircle circleWithCenterCoordinate:userLocation.coordinate radius:1000];
[map addOverlay:circle];
userLocation can be obtained by storing the MKUserLocationAnnotation as a property. Then, to actually draw the circle, put this in the map view's delegate:
- (MKOverlayRenderer *)mapView:(MKMapView *)map viewForOverlay:(id <MKOverlay>)overlay
{
MKCircleRenderer *circleView = [[MKCircleRenderer alloc] initWithOverlay:overlay];
circleView.strokeColor = [UIColor redColor];
circleView.fillColor = [[UIColor redColor] colorWithAlphaComponent:0.4];
return circleView;
}
回答2:
An updated version for iOS 8.0 using Swift.
import Foundation
import MapKit
class MapViewController: UIViewController, CLLocationManagerDelegate, MKMapViewDelegate{
var locationManager: CLLocationManager = CLLocationManager()
@IBOutlet var mapView: MKMapView!
override func viewDidLoad() {
super.viewDidLoad()
// We use a predefined location
var location = CLLocation(latitude: 46.7667 as CLLocationDegrees, longitude: 23.58 as CLLocationDegrees)
addRadiusCircle(location)
}
func addRadiusCircle(location: CLLocation){
self.mapView.delegate = self
var circle = MKCircle(centerCoordinate: location.coordinate, radius: 10000 as CLLocationDistance)
self.mapView.addOverlay(circle)
}
func mapView(mapView: MKMapView!, rendererForOverlay overlay: MKOverlay!) -> MKOverlayRenderer! {
if overlay is MKCircle {
var circle = MKCircleRenderer(overlay: overlay)
circle.strokeColor = UIColor.redColor()
circle.fillColor = UIColor(red: 255, green: 0, blue: 0, alpha: 0.1)
circle.lineWidth = 1
return circle
} else {
return nil
}
}
}
回答3:
Swift 3/ Xcode 8 here:
func addRadiusCircle(location: CLLocation){
if let poll = self.selectedPoll {
self.mapView.delegate = self
let circle = MKCircle(center: location.coordinate, radius: 10)
self.mapView.add(circle)
}
}
func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
if overlay is MKCircle {
let circle = MKCircleRenderer(overlay: overlay)
circle.strokeColor = UIColor.red
circle.fillColor = UIColor(red: 255, green: 0, blue: 0, alpha: 0.1)
circle.lineWidth = 1
return circle
} else {
return MKPolylineRenderer()
}
}
Then call like so:
self.addRadiusCircle(location: CLLocation(latitude: YOUR_LAT_HERE, longitude: YOUR_LNG_HERE))
回答4:
Try to use the code from Apple Breadcrumb example
回答5:
I didn't understand benwad answer. So here is clearer answer:
It's pretty easy to add a circle. Conform to MKMapViewDelegate
@interface MyViewController : UIViewController <MKMapViewDelegate>
@property (weak, nonatomic) IBOutlet MKMapView *mapView;
@end
In viewDidLoad, Create a circle annotation and add it to the map:
CLLocationCoordinate2D center = {39.0, -74.00};
// Add an overlay
MKCircle *circle = [MKCircle circleWithCenterCoordinate:center radius:150000];
[self.mapView addOverlay:circle];
Then implement mapView:viewForOverlay: to return the view.
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)overlay
{
MKCircleView *circleView = [[MKCircleView alloc] initWithOverlay:overlay];
[circleView setFillColor:[UIColor redColor]];
[circleView setStrokeColor:[UIColor blackColor]];
[circleView setAlpha:0.5f];
return circleView;
}
But if you want the circle to always be the same size, no matter the zoom level, you'll have to do something different. Like you say, in regionDidChange:animated:, get the latitudeDelta, then create a new circle (with a radius that fits into the width), remove the old one and add the new one.
Note from me: don't forget to connect mapview with your view controller delegate. Otherwise viewForOverlay won't be called.
回答6:
It's easy to add a circle. Conform to MKMapViewDelegate. follow the bellow steps,,,
Step 1 :
CLLocationCoordinate2D center= {self.locationManager.location.coordinate.latitude, self.locationManager.location.coordinate.longitude};
// Add an overlay
MKCircle *circle= [MKCircle circleWithCenterCoordinate:center radius: 20000];//your distance like 20000(like meters)
[myMapView addOverlay:circle];
Step 2 :
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)overlay
{
MKCircleView *C_View = [[MKCircleView alloc] initWithOverlay:overlay];
[C_View setFillColor:[UIColor lightGrayColor]];
[C_View setStrokeColor:[UIColor blackColor]];
[C_View setAlpha:0.5f];
return C_View;
}
回答7:
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)overlay
it is deprecated since iOS 4.0
回答8:
All I did is, After displaying the location on the map kit called the below function in the end.
@IBOutlet weak var mapView: GMSMapView!
var cirlce: GMSCircle!
override func viewDidLoad() {
super.viewDidLoad()
mapView.delegate = self
circleview(redius: 5000)
}
//used this func to draw the circle
func circleview(redius:Double) {
let circleCenter = CLLocationCoordinate2D(latitude: 13.3450223, longitude: 74.7512519)
cirlce = GMSCircle(position: circleCenter, radius: redius)
cirlce.fillColor = UIColor(red: 230.0/255.0, green: 230.0/255.0, blue: 250.0/255.0, alpha:1.0)
cirlce.strokeColor = .blue
cirlce.strokeWidth = 2
cirlce.map = mapView
}
来源：https://stackoverflow.com/questions/9056451/draw-a-circle-of-1000m-radius-around-users-location-in-mkmapview