Show labels on layer

View inJavaKotlin
View on GitHub
Sample viewer app

Display custom labels on a feature layer.

Image of show labels on 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 US highways will be shown.

How it works

  1. Create a ServiceFeatureTable using a feature service URL.
  2. Create a FeatureLayer from the service feature table.
  3. Create a TextSymbol to use for displaying the label text.
  4. Create an ArcadeLabelExpression for the label definition.
    • You can use fields of the feature by using $feature.field_name in the expression.
  5. Create a new LabelDefinition from the arcade label expression and text symbol.
  6. Add the definition to the feature layer with featureLayer.labelDefinitions.add(labelDefinition) .
  7. Lastly, enable labels on the layer using featureLayer.isLabelsEnabled.

Relevant API

  • FeatureLayer
  • LabelDefinition
  • TextSymbol

About the data

This sample uses the US Highways feature service 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

MainActivity.kt
Use dark colors for code blocks
                                                                                                                                         
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
/*
 * Copyright 2020 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.view.MapView
import com.esri.arcgisruntime.showlabelsonlayer.databinding.ActivityMainBinding
import com.esri.arcgisruntime.mapping.labeling.ArcadeLabelExpression
import com.esri.arcgisruntime.symbology.TextSymbol
import com.google.gson.JsonObject
import com.google.gson.JsonParser
import com.google.gson.JsonPrimitive


class MainActivity : AppCompatActivity() {

  private val TAG = MainActivity::class.java.simpleName

  private val activityMainBinding by lazy {
    ActivityMainBinding.inflate(layoutInflater)
  }

  private val mapView: MapView by lazy {
    activityMainBinding.mapView
  }

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(activityMainBinding.root)

    // 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
    val map = ArcGISMap(BasemapStyle.ARCGIS_LIGHT_GRAY)
    mapView.map = map

    // create a feature layer from an online feature service of US Congressional Districts
    val serviceFeatureTable = ServiceFeatureTable(getString(R.string.congressional_districts_url))
    val featureLayer = FeatureLayer(serviceFeatureTable)
    map.operationalLayers.add(featureLayer)

    // zoom to the layer when it's done loading
    featureLayer.addDoneLoadingListener {
      if (featureLayer.loadStatus == LoadStatus.LOADED) {
        // set viewpoint to feature layer extent
        mapView.setViewpointAsync(Viewpoint(featureLayer.fullExtent))
      } else {
        val error = "Error loading feature layer :" + featureLayer.loadError.cause
        Toast.makeText(this, error, Toast.LENGTH_LONG).show()
        Log.e(TAG, error)
      }
    }

    val republicanLabelDefinition = makeLabelDefinition("Republican", Color.RED)
    val democratLabelDefinition = makeLabelDefinition("Democrat", Color.BLUE)

    featureLayer.apply {
      // add the definitions to the feature layer
      labelDefinitions.addAll(listOf(republicanLabelDefinition, democratLabelDefinition))
      // enable labels
      isLabelsEnabled = true
    }
  }

  /**
   * Creates a label definition for a given party and color to populate a text symbol.
   *
   * @param party name to be passed into the label definition's WHERE clause
   * @param textColor to be passed into the text symbol
   *
   * @return label definition created from the given arcade expression
   */
  private fun makeLabelDefinition(party: String, textColor: Int): LabelDefinition {

    // create text symbol for styling the label
    val textSymbol = TextSymbol().apply {
      size = 12f
      color = textColor
      haloColor = Color.WHITE
      haloWidth = 2f
    }

    // create a label definition with an Arcade expression
    val arcadeLabelExpression =
      ArcadeLabelExpression("\$feature.NAME + \" (\" + left(\$feature.PARTY,1) + \")\\nDistrict \" + \$feature.CDFIPS")

    return LabelDefinition(arcadeLabelExpression, textSymbol).apply {
      placement = LabelingPlacement.POLYGON_ALWAYS_HORIZONTAL
      whereClause = String.format("PARTY = '%s'", party)
    }
  }

  override fun onPause() {
    mapView.pause()
    super.onPause()
  }

  override fun onResume() {
    super.onResume()
    mapView.resume()
  }

  override fun onDestroy() {
    mapView.dispose()
    super.onDestroy()
  }
}

Your browser is no longer supported. Please upgrade your browser for the best experience. See our browser deprecation post for more details.