Display point graphic from mouse click

johnmarker

Hello,

I want to be able to register a mouse click event and then plot a point graphic at that location. Right now I get the mouse click, get the location of that mouse click and then use those coordinates to create a graphic. After doing all this the point still does not display onto the map..

 

//MainWindow.xaml.cs

        private void MainMapView_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            MapViewModel mvm = new MapViewModel();
            Point p = e.GetPosition(MainMapView);
            MapPoint mp = MainMapView.ScreenToLocation(e.GetPosition(MainMapView));
            mvm.createPoint(mp);
        }


//MapViewModel.cs

        public void createPoint(MapPoint point)
        {
            // Create a new graphics overlay to contain a variety of graphics.
            var graphicsOverlay = new GraphicsOverlay();

            // Add the overlay to a graphics overlay collection.
            GraphicsOverlayCollection overlays = new GraphicsOverlayCollection
            {
                graphicsOverlay
            };

            // Set the view model's "GraphicsOverlays" property (will be consumed by the map view).
            this.GraphicsOverlays = overlays;

            var mapPoint = new MapPoint(point.X, point.Y, SpatialReferences.Wgs84);

            // Create a symbol to define how the point is displayed.
            var pointSymbol = new SimpleMarkerSymbol
            {
                Style = SimpleMarkerSymbolStyle.X,
                Color = System.Drawing.Color.Red,
                Size = 10.0
            };

            // Add an outline to the symbol.
            pointSymbol.Outline = new SimpleLineSymbol
            {
                Style = SimpleLineSymbolStyle.Solid,
                Color = System.Drawing.Color.Red,
                Width = 2.0
            };

            // Create a point graphic with the geometry and symbol.
            var pointGraphic = new Graphic(mapPoint, pointSymbol);

            // Add the point graphic to graphics overlay.
            graphicsOverlay.Graphics.Add(pointGraphic);
        }

NathanCastle1

When a graphic is added to a graphics overlay that is already in a mapview or sceneview, the graphic will be shown automatically, assuming there is a renderer or the graphic is configured with a symbol.

Based on the code you shared, it looks like you're following the pattern set in the template projects and the developer tutorials. If that is the case, you will see something like the following in your MainWindow.xaml file:

<Window.Resources>
    <local:MapViewModel x:Key="MapViewModel" />
</Window.Resources>

That code will create an instance of your viewmodel when InitializeComponent is called.

The MapView's Map and GraphicsOverlays properties are set via binding:

<esri:MapView x:Name="MainMapView"
              Map="{Binding Map, Source={StaticResource MapViewModel}}"
              GraphicsOverlays="{Binding GraphicsOverlays, Source={StaticResource MapViewModel}}" />

The view is bound to the specific instance of the viewmodel that is added to the `Window.Resources` dictionary. Your code is creating another instance of viewmodel, but that instance is never connected to the view in any way, so the view won't update to reflect changes in viewmodel state. You could fix this by re-setting up bindings when you create the viewmodel, or by using the existing viewmodel instance created in XAML.

I recommend updating your code to reference the copy of the ViewModel created in XAML:

You could use something like the following to get a reference to the viewmodel:

mvm = FindResource("MapViewModel") as MapViewModel;