If not rendered before adding layers it will not accept new layers

[erikthysell]

There is an issue that if the map is not rendered before adding layers, layers[mapId] is not defined and hence cannot be pushed new layers onto. I assume this is because the create function is called in OnAfterRenderAsync method.

[Mehigh17]

Could you please give a list of steps allowing to reproduce this issue?

[sylvainonweb]

Is there any news about this issue because it is really a big matter. Indeed, this arrives if I use the async version of OnInitializedAsync and OnAfterRenderAsync.

[erikthysell]

If the LeafletInterops.Create could be called in a LeafletMap.OnInitializedAsync method instead of in OnAfterRenderAsync I believe it could be averted but I am not sure if it can be done - my guess is that it can only be created on a html that is rendered...

[sylvainonweb]

In fact, the matter is the use of the Initialized event of the Map. Indeed, when you suscribe to this event, you are not sure that the OnInitializedAsync method has completed (so that your data are loaded and accessible).

To bypass this matter, I had to :

• not use the LeafletMap class which call LeafletInterops.Create on its own
• create the following method to initialize the map when I decide to do it
• add a boolean variable called OnInitializedAsyncCompleted that I set to true when OnInitializedAsync is completed (so I can check it in OnAfterRenderAsync)

        public static void Initialize(Map map, float zoom = 12F, LatLng center = null)
        {
            map.Zoom = zoom;
            if (center != null)
            {
                map.Center = center;
            }

            // Init the map
            LeafletInterops.Create(this.JSRuntime, map);
            RaiseOnInitialized(); // Mandatory else AddLayer will throw an exception

            // Do default actions
            map.AddLayer(new OpenStreetMapsTileLayer());
            map.AddFullScreen();
            map.AddLocate();
        }

which permit me to do something like this

  protected override async Task OnInitializedAsync()
        {
            this.Data= LoadData();
            await base.OnInitializedAsyncEx();
        }

        protected override void OnAfterRenderEx(bool firstRender)
        {
            if (firstRender)
            {
                this.Map.Initialize(12F);
            }
            else
            {
                if (this.OnInitializedAsyncCompleted)
                {
                    this.Map.RemoveMarkers();

                    this.Map.PanTo(new PointF(Data.X, Data.Y););
                    this.Map.AddMarker(
                        wgs84Point,
                        new Tooltip { Content = Data.Text },
                        null,
                        new Icon { Url = "XXXX" });
                }
            }

            base.OnAfterRender(firstRender);
        }