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Distance Expression

Show POIs on a map with distance expression filter.
DistanceExpressionActivity.kt
package com.mapbox.maps.testapp.examples

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import com.mapbox.geojson.Point
import com.mapbox.maps.CameraOptions
import com.mapbox.maps.MapView
import com.mapbox.maps.Style
import com.mapbox.maps.extension.style.expressions.dsl.generated.lt
import com.mapbox.maps.extension.style.layers.generated.SymbolLayer
import com.mapbox.maps.extension.style.layers.generated.fillLayer
import com.mapbox.maps.extension.style.layers.getLayer
import com.mapbox.maps.extension.style.layers.properties.generated.Visibility
import com.mapbox.maps.extension.style.sources.generated.geoJsonSource
import com.mapbox.maps.extension.style.style
import com.mapbox.turf.TurfConstants
import com.mapbox.turf.TurfTransformation

/**
* An Activity that showcases the within expression to filter features outside a geometry
*/
class DistanceExpressionActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val mapView = MapView(this)
setContentView(mapView)

val center = Point.fromLngLat(LON, LAT)
val circle = TurfTransformation.circle(center, RADIUS, TurfConstants.UNIT_METERS)

// Setup camera position above Georgetown
mapView.mapboxMap.setCamera(CameraOptions.Builder().center(center).zoom(16.0).build())

mapView.mapboxMap.loadStyle(
style(Style.MAPBOX_STREETS) {
+geoJsonSource(POINT_ID) {
geometry(center)
}
+geoJsonSource(CIRCLE_ID) {
geometry(circle)
}
+layerAtPosition(
fillLayer(CIRCLE_ID, CIRCLE_ID) {
fillOpacity(0.5)
fillColor("#3bb2d0")
},
below = POI_LABEL
)
}
) {
val symbolLayer = it.getLayer("poi-label") as SymbolLayer
symbolLayer.filter(
lt {
distance(Point.fromLngLat(LON, LAT))
literal(150)
}
)
// Hide other types of labels to highlight POI labels
(it.getLayer(ROAD_LABEL) as SymbolLayer).visibility(Visibility.NONE)
(it.getLayer(TRANSIT_LABEL) as SymbolLayer).visibility(Visibility.NONE)
(it.getLayer(ROAD_NUMBER_SHIELD) as SymbolLayer).visibility(Visibility.NONE)
}
}

companion object {
const val POINT_ID = "point"
const val CIRCLE_ID = "circle"
const val LAT = 37.78794572301525
const val LON = -122.40752220153807
const val RADIUS = 150.0
const val POI_LABEL = "poi-label"
const val ROAD_LABEL = "road-label"
const val TRANSIT_LABEL = "transit-label"
const val ROAD_NUMBER_SHIELD = "road-number-shield"
}
}
この{Type}は役に立ちましたか?