Apply unique values with alternate symbols

Apply a unique value with alternate symbols at different scales.

Use case

When a layer is symbolized with unique value symbology, you can specify the visible scale range for each unique value. This is an effective strategy to limit the amount of detailed data at smaller scales without having to make multiple versions of the layer, each with a unique definition query.

Once scale ranges are applied to unique values, you can further refine the appearance of features within those scale ranges by establishing alternate symbols to different parts of the symbol class scale range.

How to use the sample

Zoom in and out of the map to see alternate symbols at each scale. The symbology changes according to the following scale ranges: 0-5000, 5000-10000, 10000-20000. To go back to the initial viewpoint, press "Reset Viewpoint".

How it works

1. Create a FeatureLayer using the service url and add it to the map's list of operational layers.

2. Create two alternate symbols (a blue square and a yellow diamond) to be used as alternate symbols. To create an alternate symbol:

   a. Create a symbol using SimpleMarkerSymbol.

   b. Convert the simple marker symbol to a MultilayerSymbol using SimpleMarkerSymbol.ToMultilayerSymbol().

   c. Set the valid scale range through reference properties on the multilayer point symbols blue square and yellow diamond by calling MultilayerSymbol.ReferenceProperties = new SymbolReferenceProperties(double minScale, double maxScale);.

3. Create a third multilayer symbol to be used to create a UniqueValue class.

4. Create a unique value using the red triangle from step 3 and the list of alternate symbols from step 2.

5. Create a UniqueValueRenderer and add the unique value from step 4 to it.

6. Create a purple diamond simple marker and convert it to a multilayer symbol to be used as the default symbol.

7. Set the DefaultSymbol property on the unique value renderer to the purple diamond from step 6.

8. Add "req_type" to the field names on the unique value renderer.

9. Set the unique value renderer as the renderer for the feature layer.

Relevant API

• MultilayerSymbol
• SimpleMarkerSymbol
• SymbolReferenceProperties
• UniqueValue
• UniqueValueRenderer

About the data

The San Francisco 311 incidents layer in this sample displays point features related to crime incidents such as grafitti and tree damage that have been reported by city residents.

Tags

alternate symbols, scale based rendering, symbology, unique value, unique value renderer

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<ContentPage x:Class="ArcGISRuntimeXamarin.Samples.UniqueValuesAlternateSymbols.UniqueValuesAlternateSymbols"
             xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:esriUI="clr-namespace:Esri.ArcGISRuntime.Xamarin.Forms;assembly=Esri.ArcGISRuntime.Xamarin.Forms"
             xmlns:resources="clr-namespace:Forms.Resources">
    <RelativeLayout>
        <esriUI:MapView x:Name="MyMapView"
                        BindingContext="{x:Reference Name=ResponsiveFormContainer}"
                        Style="{StaticResource MapWithFormStyle}" />
        <resources:ResponsiveFormContainer x:Name="ResponsiveFormContainer">
            <StackLayout>
                <Label Margin="5" Text="{Binding Source={x:Reference MyMapView}, Path=MapScale, StringFormat='Scale: 1:{0:0}'}" />
                <Button Margin="5"
                        Padding="5"
                        Clicked="ResetViewpointClick"
                        Text="Reset viewpoint" />
            </StackLayout>
        </resources:ResponsiveFormContainer>
    </RelativeLayout>
</ContentPage>