如何在 SwiftUI 视图中调用方法

刚刚开始使用 SwiftUI。

我有一个谷歌地图视图 https://gist.github.com/kwmt/1df17577c59e33da1c4c2eb982f21bbf in a ContentView使用CLLocationManager我捕捉事件AppDelegate or SceneDelegate通过扩展它们来类CLLocationManagerDelegate.

我怎样才能调用一个方法GoogleMapsView来自AppDelegate or SceneDelegate?

在这种情况下我想调用.animate方法，当位置更改事件发送到AppDelegate实例通过CLLocationManagerDelegate，但这个问题确实更通用。

我制作并实现了 CLLocationManager 和 MKMapView，它与地图几乎相同，希望对您有所帮助：

简短回答: 声明一个@Binding var foo: Any每次 foo 更改时，您都可以在 GoogleMapView 内进行更改，在本例中 foo 是您的位置，因此您可以在每次更新 foo 时调用 animate。

长答案:

首先，我创建了一个符合 UIViewRepresentable 协议的 Mapview，就像您所做的那样，但添加了 @Binding 变量，这是我的“trigger".

MapView:

struct MapView: UIViewRepresentable {
    @Binding var location: CLLocation // Create a @Binding variable that keeps the location where I want to place the view, every time it changes updateUIView will be called
    private let zoomMeters = 400

    func makeUIView(context: UIViewRepresentableContext<MapView>) -> MKMapView {
        let mapView = MKMapView(frame: UIScreen.main.bounds)
        return mapView
    }

    func updateUIView(_ mapView: MKMapView, context: Context) {
        //When location changes, updateUIView is called, so here I move the map:
        let region = MKCoordinateRegion(center: location.coordinate,
                                        latitudinalMeters: CLLocationDistance(exactly: zoomMeters)!,
                                        longitudinalMeters: CLLocationDistance(exactly: zoomMeters)!)
        mapView.setRegion(mapView.regionThatFits(region), animated: true)
    }
}

然后我将 MapView 放置在 ContentView 中，并传递一个位置参数，接下来我将对此进行解释：

内容视图:

struct ContentView: View {

    @ObservedObject var viewModel: ContentViewModel

    var body: some View {
        VStack {
            MapView(location: self.$viewModel.location)
        }
    }
}

在我的 ViewModel 中，我使用委托处理位置更改，以下是注释中包含更多详细信息的代码：

class ContentViewModel: ObservableObject {
    //location is a Published value, so the view is updated every time location changes
    @Published var location: CLLocation = CLLocation.init()

    //LocationWorker will take care of CLLocationManager...
    let locationWorker: LocationWorker = LocationWorker()

    init() {
        locationWorker.delegate = self
    }

}

extension ContentViewModel: LocationWorkerDelegate {
    func locationChanged(lastLocation: CLLocation?) {
        //Location changed, I change the value of self.location, it is a @Published value so it will refresh the @Binding variable inside MapView and call MapView.updateUIView
        self.location = CLLocation.init(latitude: lastLocation!.coordinate.latitude, longitude: lastLocation!.coordinate.latitude)
    }
}

最后是 LocationWorker，它负责 CLLocationManager()：

class LocationWorker: NSObject, ObservableObject  {

    private let locationManager = CLLocationManager()
    var delegate: LocationWorkerDelegate?

    let objectWillChange = PassthroughSubject<Void, Never>()

    @Published var locationStatus: CLAuthorizationStatus? {
        willSet {
            objectWillChange.send()
        }
    }

    @Published var lastLocation: CLLocation? {
        willSet {
            objectWillChange.send()
        }
    }

    override init() {
        super.init()
        self.locationManager.delegate = self
        //...
    }
}

protocol LocationWorkerDelegate {
    func locationChanged(lastLocation: CLLocation?)
}

extension LocationWorker: CLLocationManagerDelegate {
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        guard let location = locations.last else { return }
        self.lastLocation = location
        //When location changes: I use my delegate ->
        if delegate != nil {
            delegate!.locationChanged(lastLocation: lastLocation)
        }
    }
}