Map layer filtering

Allow your users to apply a filter based on feature properties to only show selected layers.

Sample use case: You are using Traffic Module in your application, and you only want to show the traffic flow on Motorways.

You can achieve that by applying a filter that takes the value of the "road_type" property defined in the Traffic Vector Flow Tiles and compares it with the "Motorway" value. In this case the filter needs to be applied on layers that have a layer with an id of "Traffic flow" as their source layer.

To retrieve all those layers you can use the findLayersBySourceLayerId method as shown in the following code snippet:

//LAYERS_REGEX = "Traffic flow"
val layers = tomtomMap.styleSettings.findLayersBySourceLayerId(LAYERS_REGEX)

Once you have a list of layers, you can create the expression defining the filter (it is required to create a new instance of the expression for every layer):

1//ROAD_TYPE = "road_type"
2//ROAD_TYPE_MOTORWAY = "Motorway"
3val filteringExpression = ComparisonExpression.eq(
4    GetExpression.get(ROAD_TYPE),
5    LiteralExpression.string(ROAD_TYPE_MOTORWAY)
6)

To apply the filer you have to provide it to the setFiler method of the Layer object:

layer.setFilter(filteringExpression)

Removing the filter is done by calling the resetFilter method of the Layer object.

layer.resetFilter()