Take a web map offline.
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
- Create an
ArcGISMapwith aPortalitem pointing to the web map. - Create
GenerateOfflineMapParametersspecifying the download area geometry, minimum scale, and maximum scale. - Create an
OfflineMapTaskwith the map. - Create the
OfflineMapJobwithOfflineMapTask.generateOfflineMap(params, downloadDirectoryPath)and start it withOfflineMapJob.start(). - 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
/* Copyright 2022 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.arcgismaps.sample.generateofflinemap
import android.os.Bundle
import android.util.Log
import android.view.View
import android.view.ViewGroup
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity
import androidx.databinding.DataBindingUtil
import androidx.lifecycle.lifecycleScope
import com.arcgismaps.ApiKey
import com.arcgismaps.ArcGISEnvironment
import com.arcgismaps.Color
import com.arcgismaps.geometry.Envelope
import com.arcgismaps.mapping.ArcGISMap
import com.arcgismaps.mapping.PortalItem
import com.arcgismaps.mapping.symbology.SimpleLineSymbol
import com.arcgismaps.mapping.symbology.SimpleLineSymbolStyle
import com.arcgismaps.mapping.view.Graphic
import com.arcgismaps.mapping.view.GraphicsOverlay
import com.arcgismaps.mapping.view.ScreenCoordinate
import com.arcgismaps.portal.Portal
import com.arcgismaps.tasks.offlinemaptask.GenerateOfflineMapJob
import com.arcgismaps.tasks.offlinemaptask.GenerateOfflineMapParameters
import com.arcgismaps.tasks.offlinemaptask.OfflineMapTask
import com.esri.arcgismaps.sample.generateofflinemap.databinding.ActivityMainBinding
import com.esri.arcgismaps.sample.generateofflinemap.databinding.GenerateOfflineMapDialogLayoutBinding
import com.google.android.material.dialog.MaterialAlertDialogBuilder
import com.google.android.material.snackbar.Snackbar
import kotlinx.coroutines.launch
import java.io.File
class MainActivity : AppCompatActivity() {
// set up data binding for the activity
private val activityMainBinding: ActivityMainBinding by lazy {
DataBindingUtil.setContentView(this, R.layout.activity_main)
}
private val mapView by lazy {
activityMainBinding.mapView
}
private val takeMapOfflineButton by lazy {
activityMainBinding.takeMapOfflineButton
}
private val resetMapButton by lazy {
activityMainBinding.resetButton
}
private val graphicsOverlay: GraphicsOverlay by lazy { GraphicsOverlay() }
// create a symbol to show a box around the extent we want to download
private val downloadArea: Graphic = Graphic().apply {
symbol = SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.red, 2F)
}
private val progressDialogLayout by lazy {
GenerateOfflineMapDialogLayoutBinding.inflate(layoutInflater)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// authentication with an API key or named user is
// required to access basemaps and other location services
ArcGISEnvironment.apiKey = ApiKey.create(BuildConfig.API_KEY)
// add mapView to the lifecycle
lifecycle.addObserver(mapView)
// set up the portal item to take offline
setUpMapView()
}
/**
* Sets up a portal item and displays map area to take offline
*/
private fun setUpMapView() {
// create a portal item with the itemId of the web map
val portal = Portal(getString(R.string.portal_url))
val portalItem = PortalItem(portal, getString(R.string.item_id))
// clear graphic overlays
graphicsOverlay.graphics.clear()
mapView.graphicsOverlays.clear()
// add the download graphic to the graphics overlay
graphicsOverlay.graphics.add(downloadArea)
val map = ArcGISMap(portalItem)
lifecycleScope.launch {
map.load()
.onFailure {
showMessage(it.message.toString())
}
.onSuccess {
// limit the map scale to the largest layer scale
map.maxScale = map.operationalLayers[6].maxScale ?: 0.0
map.minScale = map.operationalLayers[6].minScale ?: 0.0
// set the map to the map view
mapView.map = map
// add the graphics overlay to the map view when it is created
mapView.graphicsOverlays.add(graphicsOverlay)
}
}
lifecycleScope.launch {
mapView.viewpointChanged.collect {
// upper left corner of the area to take offline
val minScreenPoint = ScreenCoordinate(200.0, 200.0)
// lower right corner of the downloaded area
val maxScreenPoint = ScreenCoordinate(
mapView.width - 200.0,
mapView.height - 200.0
)
// 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
}
}
}
}
/**
* Use the generate offline map job to generate an offline map.
*
* @param view: the button which calls this function
*/
fun createOfflineMapJob(view: View) {
// offline map path
val offlineMapPath = getExternalFilesDir(null)?.path + "/offlineMap"
// delete any offline map already in the cache
File(offlineMapPath).deleteRecursively()
// specify the extent, min scale, and max scale as parameters
var minScale: Double = mapView.mapScale.value
val maxScale: Double = mapView.map?.maxScale ?: 0.0
// minScale must always be larger than maxScale
if (minScale <= maxScale) {
minScale = maxScale + 1
}
// get the geometry of the downloadArea
val geometry = downloadArea.geometry
if (geometry == null) {
showMessage("Could not get geometry of the downloadArea")
return
}
// set the offline map parameters
val generateOfflineMapParameters = GenerateOfflineMapParameters(
geometry, minScale, maxScale
).apply {
// set job to cancel on any errors
continueOnErrors = false
}
// get the map from the MapView
val map = mapView.map
if (map == null) {
showMessage("Could not get map from MapView")
return
}
// create an offline map task with the map
val offlineMapTask = OfflineMapTask(map)
// create an offline map job with the download directory path and parameters and start the job
val offlineMapJob = offlineMapTask.createGenerateOfflineMapJob(
generateOfflineMapParameters,
offlineMapPath
)
// create an alert dialog to show the download progress
val progressDialog = createProgressDialog(offlineMapJob).show()
// handle offline job loading, error and succeed status
lifecycleScope.launch {
displayOfflineMapFromJob(offlineMapJob, progressDialog)
}
}
/**
* Initiates, and tracks the result of the [offlineMapJob] while displaying
* the progress to the [progressDialog]
*/
private suspend fun displayOfflineMapFromJob(
offlineMapJob: GenerateOfflineMapJob,
progressDialog: AlertDialog
) {
// create a flow-collector for the job's progress
lifecycleScope.launch {
offlineMapJob.progress.collect {
// display the current job's progress value
val progressPercentage = offlineMapJob.progress.value
progressDialogLayout.progressBar.progress = progressPercentage
progressDialogLayout.progressTextView.text = "$progressPercentage%"
}
}
// start the job
offlineMapJob.start()
offlineMapJob.result().onSuccess {
mapView.map = it.offlineMap
graphicsOverlay.graphics.clear()
// disable the button to take the map offline once the offline map is showing
takeMapOfflineButton.isEnabled = false
resetMapButton.isEnabled = true
showMessage("Map saved at: " + offlineMapJob.downloadDirectoryPath)
// close the progress dialog
progressDialog.dismiss()
}.onFailure {
progressDialog.dismiss()
showMessage(it.message.toString())
}
}
/**
* 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 MaterialAlertDialogBuilder set with the dialog layout view
*/
private fun createProgressDialog(job: GenerateOfflineMapJob): MaterialAlertDialogBuilder {
return MaterialAlertDialogBuilder(this).apply {
setTitle("Generating offline map...")
// provide a cancel button on the dialog
setNegativeButton("Cancel") { _, _ ->
lifecycleScope.launch { job.cancel() }
}
// removes parent of the progressDialog layout, if previously assigned
progressDialogLayout.root.parent?.let { parent ->
(parent as ViewGroup).removeAllViews()
}
setCancelable(false)
setView(progressDialogLayout.root)
}
}
/**
* Clear the preview map and display the Portal Item
*/
fun resetButtonClick(view: View) {
// enable offline button
takeMapOfflineButton.isEnabled = true
resetMapButton.isEnabled = false
// set up the portal item to take offline
setUpMapView()
}
private fun showMessage(message: String) {
Log.e(localClassName, message)
Snackbar.make(activityMainBinding.root, message, Snackbar.LENGTH_SHORT).show()
}
}