Annotations don't move after being placed in a MapView

Question

Created Dec ’21

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Views 1.2k

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In SwiftUI, when creating an annotation on a Map, there's no way to move an existing Annotation after it's been placed on a Map.

Example:

import SwiftUI
import MapKit

struct AnnotationItem: Identifiable {
    var id: UUID
    var coordinate: CLLocationCoordinate2D
}

struct MapTest: View {

    @Binding var annonations: [AnnotationItem]

    var body: some View {
            Map(
                coordinateRegion: $region,
                annotationItems: annotations
            ) { annotation in
                MapAnnotation(
                    coordinate: annotation.coordinate
                ) {
                     Circle()
                            .foregroundColor(.blue)
                            .frame(width: 12, height: 12)
                }
            }
        }
        .frame(width: 500, height: 500)
    }
}

extension MapTest {

    class ViewModel: ObservableObject {
        @Published var annotations: [AnnotationItem] = [
             AnnotationItem(
                 id: UUID(), 
                 coordinate: .init(latitude: 0, longitude: 0) 
             )
         ]

         // Doesn't move the annotation
         func moveTest1() {
             annotations.first?.coordinate = .init(latitude: 1, longitude: 1)
         }
         
         // Moves the annotation with a flicker
         func moveTest2() {
             annotations = [
                 AnnotationItem(
                     id: UUID(), 
                     coordinate: .init(latitude: 0, longitude: 0) 
                 )
             ]
         }
    }
}

In this example, the function move1() doesn't have any affect on the annotation, even though I think it should.

The function move2() moves the annotation, but has a flicker effect because it's creating a new AnnotationItem with a new UUID and replacing the old one.

Is this a bug? Or is there no way to smoothly animate an annotation from one location to another?

Boost

Answer 1

huajason OP

Jan ’22

Correction on moveTest1() - the code above will never work, the array should actually be modified instead:


         // Doesn't move the annotation
         func moveTest1() {
             annotations[0] = .init(latitude: 1, longitude: 1)
         }

Also, I should mention that this issue is happening on macOS using Swift UI 2

0