When SwiftUI View is set to the content of MapAnnotation, the frame does not update properly when View is changed

Question

In the body , I implemented each View in the if else syntax. Every time I click the button to toggle the boolean value and check the UI, it works perfectly as I think.

struct ContentView: View {
    
    @State private var isSelected: Bool = false
    var body: some View {
        VStack {
            if isSelected {
                Text("isSelected" )
                    .font(.title)
                    .foregroundStyle(.blue)
                    .background(.green)
            } else {
                Text("isNotSelected")
                    .font(.callout)
                    .foregroundStyle(.blue)
                    .background(.red)
            }
            
            Button("Change select state") {
                isSelected.toggle()
            }
        }
    }
}

However, the UI looks strange when the same view is just in MapAnnotation . As before, after clicking on the button to toggle the boolean value and check the UI, the Text is truncated.

struct Place: Identifiable {
    let id = UUID()
    let latitude: Double
    let longitude: Double
}

struct ContentView: View {
    
    @State private var isSelected: Bool = false
    @State private var region = MKCoordinateRegion(center: CLLocationCoordinate2D(latitude: 37.566535,
                                                                          longitude: 126.9779692),
                                           span: MKCoordinateSpan(latitudeDelta: 0.5,
                                                                  longitudeDelta: 0.5))

    let places: [Place] = [
        Place(latitude: 37.566535,
              longitude: 126.9779692),
        Place(latitude:35.1795543,
              longitude: 129.0756416)
    ]
    
    var body: some View {
        VStack {
            Map(coordinateRegion: $region,
                annotationItems: places) { place in
                
                // 🙌🏻🙌🏻🙌🏻🙌🏻 used as MapAnnotation content
                MapAnnotation(coordinate: CLLocationCoordinate2D(latitude: place.latitude,
                                                                 longitude: place.longitude)) {
                    if isSelected {
                        Text("isSelected" )
                            .font(.title)
                            .foregroundStyle(.blue)
                            .background(.green)
                    } else {
                        Text("isNotSelected")
                            .font(.callout)
                            .foregroundStyle(.blue)
                            .background(.red)
                    }
                } // MapAnnotation
            }
            
            Button("Change select state") {
                isSelected.toggle()
            }
        }
    }
}

Even if I don't use the if else syntax to seperate the View , and use a single Text View setting value with the ternary operator, the UI looks weird as before.

MapAnnotation(coordinate: CLLocationCoordinate2D(latitude: place.latitude,
                                                 longitude: place.longitude)) {
    Text(isSelected ? "isSelected" : "isNotSelected")
        .font(isSelected ? .title : .callout)
        .foregroundStyle(.blue)
        .background(isSelected ? .green : .red)
}

And when I scroll the map, the UI is updated as I expected.

Is this a SwiftUI bug? Or am I missing something?

Answer 1

Give it fixed size, for example

MapAnnotation(coordinate: CLLocationCoordinate2D(latitude: place.latitude, longitude: place.longitude)) {
    VStack {
        if isSelected {
            Text("isSelected" )
                .font(.title)
                .foregroundStyle(.blue)
                .background(.green)
        } else {
            Text("isNotSelected")
                .font(.callout)
                .foregroundStyle(.blue)
                .background(.red)
        }
    }
    .fixedSize()     // << here !!
} // MapAnnotation

Actually we don't know internal Map expectation for annotations size, so I cannot say it is a bug.