用戶在地圖上查找送貨地址，然后通過位于螢屏中間的標記來識別地址。然后通過這個標記獲得地址。如何在用戶界面中顯示地址？
struct MapView: UIViewRepresentable {
@Binding var centerCoordinate: CLLocationCoordinate2D
var currentLocation: CLLocationCoordinate2D?
var withAnnotation: MKPointAnnotation?
class Coordinator: NSObject, MKMapViewDelegate {
var parent: MapView
var addressLabel: String = "222"
init(_ parent: MapView) {
self.parent = parent
}
func mapViewDidChangeVisibleRegion(_ mapView: MKMapView) {
if !mapView.showsUserLocation {
parent.centerCoordinate = mapView.centerCoordinate
}
}
...
func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool){
let center = getCenterLocation(for: mapView)
let geoCoder = CLGeocoder()
geoCoder.reverseGeocodeLocation(center) { [weak self] (placemarks, error) in
guard let self = self else { return }
if let _ = error {
//TODO: Show alert informing the user
print("error")
return
}
guard let placemark = placemarks?.first else {
//TODO: Show alert informing the user
return
}
let streetNumber = placemark.subThoroughfare ?? ""
let streetName = placemark.thoroughfare ?? ""
DispatchQueue.main.async {
self.addressLabel = String("\(streetName) | \(streetNumber)")
print(self.addressLabel)
}
}
}
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIView(context: Context) -> MKMapView {
let mapView = MKMapView()
mapView.delegate = context.coordinator
mapView.showsUserLocation = false
return mapView
}
func updateUIView(_ uiView: MKMapView, context: Context) {
if let currentLocation = self.currentLocation {
if let annotation = self.withAnnotation {
uiView.removeAnnotation(annotation)
}
uiView.showsUserLocation = true
let region = MKCoordinateRegion(center: currentLocation, latitudinalMeters: 1000, longitudinalMeters: 1000)
uiView.setRegion(region, animated: true)
} else if let annotation = self.withAnnotation {
uiView.removeAnnotations(uiView.annotations)
uiView.addAnnotation(annotation)
}
}
}
我正在嘗試將地址傳遞給 UI。執行此操作的最正確方法是什么？在界面中，我想從一個不斷變化的變數addressLabel中獲取地址
import SwiftUI
import MapKit
fileprivate let locationFetcher = LocationFetcher()
struct LocationView: View {
@State var centerCoordinate = CLLocationCoordinate2D()
@State var currentLocation: CLLocationCoordinate2D?
@State var annotation: MKPointAnnotation?
var body: some View {
ZStack {
MapView(centerCoordinate: $centerCoordinate, currentLocation: currentLocation, withAnnotation: annotation)
.edgesIgnoringSafeArea([.leading, .trailing, .bottom])
.onAppear(perform: {
locationFetcher.start()
})
}
.overlay(
ZStack {
Text("\(*MapView(centerCoordinate: $centerCoordinate, currentLocation: currentLocation, withAnnotation: annotation).makeCoordinator().addressLabel OMG????*)")
.offset(y: 44)
}
)
}
struct LocationView_Previews: PreviewProvider {
static var previews: some View {
LocationView()
}
}
我怎樣才能做到這一點 ？
提前致謝
uj5u.com熱心網友回復：
這是一種方法。擁有 UIKit 和 SwiftUI 都可以訪問的單一事實來源。
@available(iOS 15.0, *)
struct LocationView: View {
//It is better to have one source of truth
@StateObject var vm: MapViewModel = MapViewModel()
var body: some View {
ZStack {
MapView(vm: vm)
.edgesIgnoringSafeArea([.leading, .trailing, .bottom])
.onAppear(perform: {
//locationFetcher.start() //No Code provided
})
}
.overlay(
HStack{
Spacer()
Text(vm.addressLabel)
Spacer()
//Using offset is subjective since screen sizes change just center it
}
)
//Sample alert that adapts to what is
.alert(isPresented: $vm.errorAlert.isPresented, error: vm.errorAlert.error, actions: {
if vm.errorAlert.defaultAction != nil{
Button("ok", role: .none, action: vm.errorAlert.defaultAction!)
}
if vm.errorAlert.cancelAction != nil{
Button("cancel", role: .cancel, action: vm.errorAlert.cancelAction!)
}
if vm.errorAlert.defaultAction == nil && vm.errorAlert.cancelAction == nil {
Button("ok", role: .none, action: {})
}
})
}
}
//UIKit and SwiftUI will have access to this ViewModel so all the data can have one souce of truth
class MapViewModel: ObservableObject{
//All the variables live here
@Published var addressLabel: String = "222"
@Published var centerCoordinate: CLLocationCoordinate2D = CLLocationCoordinate2D()
@Published var currentLocation: CLLocationCoordinate2D? = nil
@Published var withAnnotation: MKPointAnnotation? = nil
@Published var annotation: MKPointAnnotation?
//This tuple variable allows you to have a dynamic alert in the view
@Published var errorAlert: (isPresented: Bool, error: MapErrors, defaultAction: (() -> Void)?, cancelAction: (() -> Void)?) = (false, MapErrors.unknown, nil, nil)
//The new alert requires a LocalizedError
enum MapErrors: LocalizedStringKey, LocalizedError{
case unknown
case failedToRetrievePlacemark
case failedToReverseGeocode
case randomForTestPurposes
//Add localizable.strings to you project and add these keys so you get localized messages
var errorDescription: String?{
switch self{
case .unknown:
return "unknown".localizedCapitalized
case .failedToRetrievePlacemark:
return "failedToRetrievePlacemark".localizedCapitalized
case .failedToReverseGeocode:
return "failedToReverseGeocode".localizedCapitalized
case .randomForTestPurposes:
return "randomForTestPurposes".localizedCapitalized
}
}
}
//Presenting with this will ensure that errors keep from gettting lost by creating a loop until they can be presented
func presentError(isPresented: Bool, error: MapErrors, defaultAction: (() -> Void)?, cancelAction: (() -> Void)?, count: Int = 1){
//If there is an alert already showing
if errorAlert.isPresented{
//See if the current error has been on screen for 10 seconds
if count >= 10{
//If it has dismiss it so the new error can be posted
errorAlert.isPresented = false
}
//Call the method again in 1 second
DispatchQueue.main.asyncAfter(deadline: .now() 1) {
let newCount = count 1
self.presentError(isPresented: isPresented, error: error, defaultAction: defaultAction, cancelAction: cancelAction, count: newCount)
}
}else{
errorAlert = (isPresented, error, defaultAction, cancelAction)
}
}
}
struct MapView: UIViewRepresentable {
@ObservedObject var vm: MapViewModel
class Coordinator: NSObject, MKMapViewDelegate {
var parent: MapView
init(_ parent: MapView) {
self.parent = parent
}
func mapViewDidChangeVisibleRegion(_ mapView: MKMapView) {
if !mapView.showsUserLocation {
parent.vm.centerCoordinate = mapView.centerCoordinate
}
}
func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool){
getAddress(center: mapView.centerCoordinate)
//Just to demostrate the error
//You can remove this whenever
#if DEBUG
if Bool.random(){
self.parent.vm.presentError(isPresented: true, error: MapViewModel.MapErrors.randomForTestPurposes, defaultAction: nil, cancelAction: nil)
}
#endif
}
//Gets the addess from CLGeocoder if available
func getAddress(center: CLLocationCoordinate2D){
let geoCoder = CLGeocoder()
geoCoder.reverseGeocodeLocation(CLLocation(latitude: center.latitude, longitude: center.longitude)) { [weak self] (placemarks, error) in
guard let self = self else { return }
if let _ = error {
//TODO: Show alert informing the user
print("error")
self.parent.vm.presentError(isPresented: true, error: MapViewModel.MapErrors.failedToReverseGeocode, defaultAction: nil, cancelAction: nil)
return
}
guard let placemark = placemarks?.first else {
//TODO: Show alert informing the user
self.parent.vm.presentError(isPresented: true, error: MapViewModel.MapErrors.failedToRetrievePlacemark, defaultAction: nil, cancelAction: nil)
return
}
let streetNumber = placemark.subThoroughfare ?? ""
let streetName = placemark.thoroughfare ?? ""
DispatchQueue.main.async {
self.parent.vm.addressLabel = String("\(streetName) | \(streetNumber)")
print(self.parent.vm.addressLabel)
}
}
}
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIView(context: Context) -> MKMapView {
let mapView = MKMapView()
mapView.delegate = context.coordinator
mapView.showsUserLocation = false
return mapView
}
func updateUIView(_ uiView: MKMapView, context: Context) {
if let currentLocation = vm.currentLocation {
if let annotation = vm.withAnnotation {
uiView.removeAnnotation(annotation)
}
uiView.showsUserLocation = true
let region = MKCoordinateRegion(center: currentLocation, latitudinalMeters: 1000, longitudinalMeters: 1000)
uiView.setRegion(region, animated: true)
} else if let annotation = vm.withAnnotation {
uiView.removeAnnotations(uiView.annotations)
uiView.addAnnotation(annotation)
}
}
}
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