Display custom labels on a feature layer.
Use case
Labeling features is useful to visually display a key piece of information or attribute of a feature on a map. For example, you may want to label rivers or streets with their names.
How to use the sample
Pan and zoom around the United States. Labels for congressional districts will be shown in red for Republican districts and blue for Democrat districts. Notice how labels pop into view as you zoom in.
How it works
- Create a
ServiceFeatureTable
using a feature service URL. - Create a
FeatureLayer
from the service feature table. - Create a
TextSymbol
to use for displaying the label text. - Create an
ArcadeLabelExpression
for the label definition.- You can use fields of the feature by using
$feature.field_name
in the expression.
- You can use fields of the feature by using
- Create a new
LabelDefinition
from the arcade label expression and text symbol. - Add the definition to the feature layer with
featureLayer.labelDefinitions.add(labelDefinition)
. - Lastly, enable labels on the layer using
featureLayer.setLabelsEnabled()
.
Relevant API
- ArcadeLabelExpression
- FeatureLayer
- LabelDefinition
- TextSymbol
About the data
This sample uses the USA 116th Congressional Districts feature layer hosted on ArcGIS Online.
Additional information
Help regarding the Arcade label expression script for defining a label definition can be found on the ArcGIS Developers site.
Tags
arcade, attribute, deconfliction, label, labeling, string, symbol, text, visualization
Sample Code
/*
* Copyright 2018 Esri
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package com.esri.arcgisruntime.showlabelsonlayer;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.arcgisservices.LabelDefinition;
import com.esri.arcgisruntime.arcgisservices.LabelingPlacement;
import com.esri.arcgisruntime.data.ServiceFeatureTable;
import com.esri.arcgisruntime.layers.FeatureLayer;
import com.esri.arcgisruntime.loadable.LoadStatus;
import com.esri.arcgisruntime.mapping.ArcGISMap;
import com.esri.arcgisruntime.mapping.BasemapStyle;
import com.esri.arcgisruntime.mapping.Viewpoint;
import com.esri.arcgisruntime.mapping.labeling.ArcadeLabelExpression;
import com.esri.arcgisruntime.mapping.view.MapView;
import com.esri.arcgisruntime.symbology.TextSymbol;
import java.util.Arrays;
public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName();
private MapView mMapView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// authentication with an API key or named user is required to access basemaps and other
// location services
ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY);
// create a map view and set a map
mMapView = findViewById(R.id.mapView);
ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_LIGHT_GRAY);
mMapView.setMap(map);
// create a feature layer from an online feature service of US Congressional Districts
ServiceFeatureTable serviceFeatureTable = new ServiceFeatureTable(getString(R.string.congressional_districts_url));
FeatureLayer featureLayer = new FeatureLayer(serviceFeatureTable);
map.getOperationalLayers().add(featureLayer);
// zoom to the layer when it's done loading
featureLayer.addDoneLoadingListener(() -> {
if (featureLayer.getLoadStatus() == LoadStatus.LOADED) {
// set viewpoint to feature layer extent
mMapView.setViewpointAsync(new Viewpoint(featureLayer.getFullExtent()));
} else {
String error = "Error loading feature layer :" + featureLayer.getLoadError().getCause();
Toast.makeText(this, error, Toast.LENGTH_LONG).show();
Log.e(TAG, error);
}
});
LabelDefinition republicanLabelDefinition = makeLabelDefinition("Republican", Color.RED);
LabelDefinition democratLabelDefinition = makeLabelDefinition("Democrat", Color.BLUE);
// add the definitions to the feature layer
featureLayer.getLabelDefinitions().addAll(Arrays.asList(republicanLabelDefinition, democratLabelDefinition));
// enable labels
featureLayer.setLabelsEnabled(true);
}
/**
* Creates a label definition for a given party (field value) and color to populate a text symbol with.
*
* @param party the name of the party to be passed into the label definition's WHERE clause
* @param textColor the color to be passed into the text symbol
*
* @return label definition created from the given arcade expression
*/
private LabelDefinition makeLabelDefinition(String party, int textColor) {
// create text symbol for styling the label
TextSymbol textSymbol = new TextSymbol();
textSymbol.setSize(12);
textSymbol.setColor(textColor);
textSymbol.setHaloColor(Color.WHITE);
textSymbol.setHaloWidth(2);
// create a label definition with an Arcade expression script
ArcadeLabelExpression arcadeLabelExpression =
new ArcadeLabelExpression("$feature.NAME + \" (\" + left($feature.PARTY,1) + \")\\nDistrict \" + $feature.CDFIPS");
LabelDefinition labelDefinition = new LabelDefinition(arcadeLabelExpression, textSymbol);
labelDefinition.setPlacement(LabelingPlacement.POLYGON_ALWAYS_HORIZONTAL);
labelDefinition.setWhereClause(String.format("PARTY = '%s'", party));
return labelDefinition;
}
@Override
protected void onPause() {
mMapView.pause();
super.onPause();
}
@Override
protected void onResume() {
super.onResume();
mMapView.resume();
}
@Override
protected void onDestroy() {
mMapView.dispose();
super.onDestroy();
}
}