Call method when the location of the annotation becomes visible on the custom map Xamarin.Android

Question

This post is continuation of this topic I need find equivalent method Xamarin.Forms.Maps.iOS.MapRenderer.GetViewForAnnotation for CustomMapRenderer for Android. As for this documentation the GetViewForAnnotation method for iOS is called when the location of the annotation becomes visible on the map, and is used to customize the annotation prior to display. I need to find equivalent because I want to show pins on my map with already expanded window message(without click on them).

Answer 1

You could show the InfoWindow directly after you get the marker from your custom pin.

Add the code below when you override the CreateMarker method.

NativeMap.AddMarker(marker).ShowInfoWindow();

The whold custom renderer of Android:

  public class CustomMapRenderer : MapRenderer, GoogleMap.IInfoWindowAdapter
{
    List<CustomPin> customPins;


    public CustomMapRenderer(Context context) : base(context)
    {
    }
    protected override void OnElementChanged(ElementChangedEventArgs<Map> e)
    {
        base.OnElementChanged(e);
        if (e.OldElement != null)
        {
            NativeMap.InfoWindowClick -= OnInfoWindowClick;
        }

        if (e.NewElement != null)
        {
            var formsMap = (CustomMap)e.NewElement;
            customPins = formsMap.CustomPins;
        }
    }


    protected override void OnMapReady(GoogleMap map)
    {
        base.OnMapReady(map);


        NativeMap.InfoWindowClick += OnInfoWindowClick;
        NativeMap.SetInfoWindowAdapter(this);

    }
    protected override MarkerOptions CreateMarker(Pin pin)
    {
        var marker = new MarkerOptions();
        marker.SetPosition(new LatLng(pin.Position.Latitude, pin.Position.Longitude));
        marker.SetTitle(pin.Label);
        marker.SetSnippet(pin.Address);
        marker.SetIcon(BitmapDescriptorFactory.FromResource(Resource.Drawable.pin));

        NativeMap.AddMarker(marker).ShowInfoWindow();

        return marker;
    }


    private void OnInfoWindowClick(object sender, GoogleMap.InfoWindowClickEventArgs e)
    {
        var customPin = GetCustomPin(e.Marker);
        if (customPin == null)
        {
            throw new Exception("Custom pin not found");
        }

        if (!string.IsNullOrWhiteSpace(customPin.Url))
        {
            var url = Android.Net.Uri.Parse(customPin.Url);
            var intent = new Intent(Intent.ActionView, url);
            intent.AddFlags(ActivityFlags.NewTask);
            Android.App.Application.Context.StartActivity(intent);
        }
    }

    CustomPin GetCustomPin(Marker annotation)
    {
        var position = new Position(annotation.Position.Latitude, annotation.Position.Longitude);
        foreach (var pin in customPins)
        {
            if (pin.Position == position)
            {
                return pin;
            }
        }
        return null;
    }

    public Android.Views.View GetInfoContents(Marker marker)
    {
        var inflater = Android.App.Application.Context.GetSystemService(Context.LayoutInflaterService) as Android.Views.LayoutInflater;
        if (inflater != null)
        {
            Android.Views.View view;

            var customPin = GetCustomPin(marker);
            if (customPin == null)
            {
                throw new Exception("Custom pin not found");
            }

            if (customPin.Name.Equals("Xamarin"))
            {
                view = inflater.Inflate(Resource.Layout.XamarinMapInfoWindow, null);
            }
            else
            {
                view = inflater.Inflate(Resource.Layout.MapInfoWindow, null);
            }

            var infoTitle = view.FindViewById<TextView>(Resource.Id.InfoWindowTitle);
            var infoSubtitle = view.FindViewById<TextView>(Resource.Id.InfoWindowSubtitle);

            if (infoTitle != null)
            {
                infoTitle.Text = marker.Title;
            }
            if (infoSubtitle != null)
            {
                infoSubtitle.Text = marker.Snippet;
            }

            return view;
        }
        return null;
    }

    public Android.Views.View GetInfoWindow(Marker marker)
    {

        return null;
    }
}

For more details, you could refer to the MS docs. https://learn.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/custom-renderer/map-pin