map_content.swift

import SwiftUI
import MapKit

struct Point: Identifiable {
	var id = UUID()
	var latitude, longitude: Double
	func coordinate() -> CLLocationCoordinate2D {
		CLLocationCoordinate2D(latitude: latitude, longitude: longitude)
	}
}
let defaultMapCenter = CLLocationCoordinate2D(latitude: 30.551, longitude: 104.07)
let defaultMapRegion = MKCoordinateRegion(center: defaultMapCenter, latitudinalMeters: 1000, longitudinalMeters: 10000)
let defaultPoints = [
	Point(latitude: defaultMapCenter.latitude+0.01, longitude: defaultMapCenter.longitude+0.01),
	Point(latitude: defaultMapCenter.latitude+0.02, longitude: defaultMapCenter.longitude+0.02),
	Point(latitude: defaultMapCenter.latitude+0.03, longitude: defaultMapCenter.longitude+0.03),
	Point(latitude: defaultMapCenter.latitude+0.04, longitude: defaultMapCenter.longitude+0.04),
]
struct ContentView: View {
	@State var mapRegion = defaultMapRegion
	@State var annotations: [Point] = defaultPoints

	var body: some View {
		VStack{
			Map(coordinateRegion: $mapRegion, annotationItems: annotations) { point in
				//使用MapMarker是不会报错的
				MapMarker(coordinate: point.coordinate(),tint: .red)
				//使用MapAnnotation，一旦地图发生变化，比如随意拖动下，会大量的报下面的错误
				//Publishing changes from within view updates is not allowed, this will cause undefined behavior
//				MapAnnotation(coordinate: point.coordinate()) {
//					Rectangle().stroke(Color.blue).frame(width: 20, height: 20)
//				}
			}
			Map(coordinateRegion: $mapRegion, annotationItems: annotations) { point in
				MapAnnotation(coordinate: point.coordinate()) {
					Rectangle().stroke(Color.blue).frame(width: 20, height: 20)
				}
			}
		}
	}
}

struct DemoView_Previews: PreviewProvider {
	static var previews: some View {
		ContentView()
	}
}