Generate offline map

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Take a web map offline.

Image of generate offline map

Use case

Taking a web map offline allows users continued productivity when their network connectivity is poor or nonexistent. For example, by taking a map offline, a field worker inspecting utility lines in remote areas could still access a feature's location and attribute information.

How to use the sample

Once the map loads, zoom to the extent you want to take offline. The red border shows the extent that will be downloaded. Tap the "Take Map Offline" button to start the offline map job. The progress bar will show the job's progress. When complete, the offline map will replace the online map in the map view.

How it works

  1. Create an ArcGISMap with a Portal item pointing to the web map.
  2. Create GenerateOfflineMapParameters specifying the download area geometry, minimum scale, and maximum scale.
  3. Create an OfflineMapTask with the map.
  4. Create the OfflineMapJob with OfflineMapTask.generateOfflineMap(params, downloadDirectoryPath) and start it with OfflineMapJob.start().
  5. When the job is done, get the offline map with OfflineMapJob.result.offlineMap.

Relevant API

  • GenerateOfflineMapJob
  • GenerateOfflineMapParameters
  • GenerateOfflineMapResult
  • OfflineMapTask
  • Portal

About the data

The map used in this sample shows the stormwater network within Naperville, IL, USA, with cartography designed for web and mobile devices with offline support.

Additional information

The creation of the offline map can be fine-tuned using parameter overrides for feature layers, or by using local basemaps to achieve more customised results.

Tags

download, offline, save, web map

Sample Code

MainActivity.kt
                                                                                                                                                                                                                                                       
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/*
 * 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.sample.generateofflinemap

import android.app.AlertDialog
import android.graphics.Color
import android.graphics.Point
import android.os.Bundle
import android.util.Log
import android.view.View
import android.widget.Button
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import com.esri.arcgisruntime.ArcGISRuntimeEnvironment
import com.esri.arcgisruntime.concurrent.Job
import com.esri.arcgisruntime.geometry.Envelope
import com.esri.arcgisruntime.loadable.LoadStatus
import com.esri.arcgisruntime.mapping.ArcGISMap
import com.esri.arcgisruntime.mapping.view.Graphic
import com.esri.arcgisruntime.mapping.view.GraphicsOverlay
import com.esri.arcgisruntime.mapping.view.MapView
import com.esri.arcgisruntime.portal.Portal
import com.esri.arcgisruntime.portal.PortalItem
import com.esri.arcgisruntime.sample.generateofflinemap.databinding.ActivityMainBinding
import com.esri.arcgisruntime.sample.generateofflinemap.databinding.DialogLayoutBinding
import com.esri.arcgisruntime.security.AuthenticationManager
import com.esri.arcgisruntime.security.DefaultAuthenticationChallengeHandler
import com.esri.arcgisruntime.symbology.SimpleLineSymbol
import com.esri.arcgisruntime.tasks.offlinemap.GenerateOfflineMapJob
import com.esri.arcgisruntime.tasks.offlinemap.GenerateOfflineMapParameters
import com.esri.arcgisruntime.tasks.offlinemap.OfflineMapTask
import java.io.File

class MainActivity : AppCompatActivity() {

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

  private val tempDirectoryPath: String by lazy {
    cacheDir.toString() + "/offlineMap"
  }

  private val graphicsOverlay: GraphicsOverlay by lazy { GraphicsOverlay() }

  private val downloadArea: Graphic by lazy { Graphic() }

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

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

  private val takeMapOfflineButton: Button by lazy {
    activityMainBinding.takeMapOfflineButton
  }

  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)

    // disable the button until the map is loaded
    takeMapOfflineButton.isEnabled = false

    // create a portal item with the itemId of the web map
    val portal = Portal(getString(R.string.portal_url), false)
    val portalItem = PortalItem(portal, getString(R.string.item_id))

    // create a map with the portal item
    val map = ArcGISMap(portalItem).apply {
      addDoneLoadingListener {
        if (loadStatus == LoadStatus.LOADED) {
          // limit the map scale to the largest layer scale
          maxScale = operationalLayers[6].maxScale
          minScale = operationalLayers[6].minScale
        } else {
          val error = "Map failed to load: " + loadError.message
          Toast.makeText(this@MainActivity, error, Toast.LENGTH_LONG).show()
          Log.e(TAG, error)
        }
      }
    }

    // create a symbol to show a box around the extent we want to download
    downloadArea.symbol = SimpleLineSymbol(SimpleLineSymbol.Style.SOLID, Color.RED, 2F)
    // add the graphic to the graphics overlay when it is created
    graphicsOverlay.graphics.add(downloadArea)

    mapView.apply {
      // set the map to the map view
      this.map = map
      // add the graphics overlay to the map view when it is created
      graphicsOverlays.add(graphicsOverlay)
      // update the download area box whenever the viewpoint changes
      addViewpointChangedListener {
        if (map.loadStatus == LoadStatus.LOADED) {
          // upper left corner of the area to take offline
          val minScreenPoint = Point(200, 200)
          // lower right corner of the downloaded area
          val maxScreenPoint = Point(
            mapView.width - 200,
            mapView.height - 200
          )
          // convert screen points to map points
          val minPoint = mapView.screenToLocation(minScreenPoint)
          val maxPoint = mapView.screenToLocation(maxScreenPoint)
          // use the points to define and return an envelope
          if (minPoint != null && maxPoint != null) {
            val envelope = Envelope(minPoint, maxPoint)
            downloadArea.geometry = envelope
            // enable the take map offline button only after the map is loaded
            if (!takeMapOfflineButton.isEnabled) takeMapOfflineButton.isEnabled = true
          }
        }
      }
    }
  }

  /**
   * Use the generate offline map job to generate an offline map.
   *
   * @param view: the button which calls this function
   */
  fun generateOfflineMap(view: View) {
    // delete any offline map already in the cache
    File(tempDirectoryPath).deleteRecursively()

    // specify the extent, min scale, and max scale as parameters
    var minScale: Double = mapView.mapScale
    val maxScale: Double = mapView.map.maxScale
    // minScale must always be larger than maxScale
    if (minScale <= maxScale) {
      minScale = maxScale + 1
    }

    val generateOfflineMapParameters = GenerateOfflineMapParameters(
      downloadArea.geometry, minScale, maxScale
    ).apply {
      // set job to cancel on any errors
      isContinueOnErrors = false
    }
    // create an offline map task with the map
    val offlineMapTask = OfflineMapTask(mapView.map)

    // create an offline map job with the download directory path and parameters and start the job
    val offlineMapJob =
      offlineMapTask.generateOfflineMap(generateOfflineMapParameters, tempDirectoryPath)

    // create an alert dialog to show the download progress
    val progressDialogLayoutBinding = DialogLayoutBinding.inflate(layoutInflater)
    val progressDialog = createProgressDialog(offlineMapJob)
    progressDialog.setView(progressDialogLayoutBinding.root)
    progressDialog.show()

    offlineMapJob.apply {
      // link the progress bar to the job's progress
      addProgressChangedListener {
        progressDialogLayoutBinding.progressBar.progress = progress
        progressDialogLayoutBinding.progressTextView.text = "${progress}%"
      }

      // replace the current map with the result offline map when the job finishes
      addJobDoneListener {
        if (status == Job.Status.SUCCEEDED) {
          val result = result
          mapView.map = result.offlineMap
          graphicsOverlay.graphics.clear()

          // disable and remove the button to take the map offline once the offline map is showing
          takeMapOfflineButton.isEnabled = false
          takeMapOfflineButton.visibility = View.GONE

          Toast.makeText(
            this@MainActivity,
            "Now displaying offline map.",
            Toast.LENGTH_LONG
          ).show()
        } else {
          val error =
            "Error in generate offline map job: " + offlineMapJob.error.message
          Toast.makeText(this@MainActivity, error, Toast.LENGTH_LONG).show()
          Log.e(TAG, error)
        }
        // close the progress dialog
        progressDialog.dismiss()
      }
      // start the job
      start()
    }
  }

  /**
   * Create a progress dialog box for tracking the generate offline map job.
   *
   * @param job the generate offline map job progress to be tracked
   * @return an AlertDialog set with the dialog layout view
   */
  private fun createProgressDialog(job: GenerateOfflineMapJob): AlertDialog {
    val builder = AlertDialog.Builder(this@MainActivity).apply {
      setTitle("Generating offline map...")
      // provide a cancel button on the dialog
      setNegativeButton("Cancel") { _, _ ->
        job.cancel()
      }
      setCancelable(true)
      val dialogLayoutBinding = DialogLayoutBinding.inflate(layoutInflater)
      setView(dialogLayoutBinding.root)
    }
    return builder.create()
  }

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

  override fun onPause() {
    mapView.pause()
    // delete the temporary cache when the app loses focus
    File(tempDirectoryPath).deleteRecursively()
    super.onPause()
  }

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

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