Xamarin Forms Android MapRenderer

Question

我已成功为Xamarin iOS创建了ViewRenderer，现在尝试为Android实现Renderer，这是我需要在Android中实现的Map：

public class MapViewModel : Map
    {
        public static readonly BindableProperty LocationsProperty = BindableProperty.Create<MapViewModel, List<Branch>>(x => x.Locations, new List<Branch>());
        public static readonly BindableProperty PinTappedCommandProperty = BindableProperty.Create<MapViewModel, Command>(x => x.PinTapped, null);

        public MapViewModel(List<Branch> locations)
        {
            Locations = locations;
            PinTapped = new Command(async (x) =>
                {
                    //await Navigation.PopModalAsync();
                    var info = new InformationView((Branch)x);
                    await Navigation.PushAsync(info);
                });
        }

        public List<Branch> Locations
        {
            get { return (List<Branch>)GetValue(LocationsProperty); }
            set { SetValue(LocationsProperty, value); }
        }

        public Command PinTapped 
        {
            get {return (Command) GetValue(PinTappedCommandProperty); }
            set {SetValue(PinTappedCommandProperty, value);}
        }
    }

按照我为iOS所做的操作，我为Android执行了以下操作：

[assembly: ExportRenderer (typeof (MapViewModel), typeof (MapViewAndroid))]
public class MapViewAndroid : ViewRenderer<MapViewModel, global::Android.Gms.Maps.MapView>
    {
        private global::Android.Gms.Maps.MapView NativeMap {get { return Control; } }

        public MapViewAndroid ()
        {
        }
        protected override void OnElementPropertyChanged (object sender, System.ComponentModel.PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged (sender, e);
        }
        protected override void OnElementChanged (ElementChangedEventArgs<MapViewModel> e)
        {
            base.OnElementChanged(e);
            var map = e.NewElement;
            var cmd = map.PinTapped;
            SetNativeControl(NativeMap);
        }
}

Control为null，因此我无法正确设置SetNativeControl ，在应用程序输出中，我读到了： [art] JNI RegisterNativeMethods: attempt to register 0 native methods for kimo.customersapp.android.MapViewAndroid作品？

Answer 1

Google地图可能需要一些时间才能初始化。 您需要等待它完全加载后才能使用它。 另外，请确保您已插入IOnMapReadyCallback，以便在准备使用地图时收到通知。

private GoogleMap NativeMap { get;set;}
protected override void OnElementPropertyChanged (object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
    base.OnElementPropertyChanged (sender, e);
    if (e.PropertyName.Equals ("VisibleRegion")) {
        var targetElement = (Android.Gms.Maps.MapView)Control;
        if (NativeMap == null) {
            targetElement.GetMapAsync (this);
        }
    }

}