Within expression
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This example code is part of the Maps SDK for Android Examples App, a working Android project available on GitHub. Android developers are encouraged to run the examples app locally to interact with this example in an emulator and explore other features of the Maps SDK.
See our Run the Maps SDK for Android Examples App tutorial for step-by-step instructions.
WithinExpressionActivity.kt
package com.mapbox.maps.testapp.examples
import android.graphics.Color
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import com.mapbox.geojson.*
import com.mapbox.maps.CameraOptions
import com.mapbox.maps.MapView
import com.mapbox.maps.Style
import com.mapbox.maps.extension.style.expressions.dsl.generated.within
import com.mapbox.maps.extension.style.layers.addLayerBelow
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.generated.lineLayer
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.maps.plugin.animation.MapAnimationOptions.Companion.mapAnimationOptions
import com.mapbox.maps.plugin.animation.camera
/**
* An Activity that showcases the within expression to filter features outside a geometry
*/
class WithinExpressionActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val mapView = MapView(this)
setContentView(mapView)
val center = Point.fromLngLat(LON, LAT)
// Setup camera position above Georgetown
mapView.mapboxMap.setCamera(
CameraOptions.Builder()
.center(center)
.zoom(15.5)
.build()
)
// Assume the route is represented by an array of coordinates.
val coordinates = listOf<Point>(
Point.fromLngLat(
-77.06866264343262,
38.90506061276737
),
Point.fromLngLat(
-77.06283688545227,
38.905194197410545
),
Point.fromLngLat(
-77.06285834312439,
38.906429843444094
),
Point.fromLngLat(
-77.0630407333374,
38.90680554236621
)
)
// Create buffer around linestring
val bufferedRouteGeometry = bufferLineStringGeometry()
mapView.mapboxMap.loadStyle(
style(Style.MAPBOX_STREETS) {
+geoJsonSource(POINT_ID) {
geometry(LineString.fromLngLats(coordinates))
}
+geoJsonSource(FILL_ID) {
featureCollection(FeatureCollection.fromFeature(Feature.fromGeometry(bufferedRouteGeometry)))
buffer(0)
tolerance(0.0)
}
+layerAtPosition(
lineLayer(LINE_ID, POINT_ID) {
lineWidth(7.5)
lineColor(Color.LTGRAY)
},
below = POI_LABEL
)
}
) { // Add fill layer to represent buffered LineString
it.addLayerBelow(
fillLayer(FILL_ID, FILL_ID) {
fillOpacity(0.12)
fillColor(Color.YELLOW)
},
LINE_ID
)
// Move to a new camera position
mapView.camera.easeTo(
CameraOptions.Builder()
.zoom(16.0)
.center(Point.fromLngLat(-77.06535338052844, 38.905156245642814))
.bearing(80.68015859462369)
.pitch(55.0)
.build(),
mapAnimationOptions {
duration(1750)
startDelay(2000)
}
)
// Show only POI labels inside geometry using within expression
val symbolLayer = it.getLayer(POI_LABEL) as SymbolLayer
symbolLayer.filter(within(bufferedRouteGeometry))
// 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
)
}
}
private fun bufferLineStringGeometry(): Polygon {
// TODO replace static data by Turf#Buffer: mapbox-java/issues/987
return FeatureCollection.fromJson(
"""
{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"properties": {},
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
-77.06867337226866,
38.90467655551809
],
[
-77.06233263015747,
38.90479344272695
],
[
-77.06234335899353,
38.906463238984344
],
[
-77.06290125846863,
38.907206285691615
],
[
-77.06364154815674,
38.90684728656818
],
[
-77.06326603889465,
38.90637140121084
],
[
-77.06321239471436,
38.905561553883246
],
[
-77.0691454410553,
38.905436318935635
],
[
-77.06912398338318,
38.90466820642439
],
[
-77.06867337226866,
38.90467655551809
]
]
]
}
}
]
}
""".trimIndent()
).features()!![0].geometry() as Polygon
}
companion object {
const val POINT_ID = "point"
const val FILL_ID = "fill"
const val LINE_ID = "line"
const val LAT = 38.90628988399711
const val LON = -77.06574689337494
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"
}
}
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