Generate offline map (overrides)

View on GitHub

Sample viewer app

Take a web map offline with additional options for each layer.

Image of generate offline map overrides

Use case

When taking a web map offline, you may adjust the data (such as layers or tiles) that is downloaded by using custom parameter overrides. This can be used to reduce the extent of the map or the download size of the offline map. It can also be used to highlight specific data by removing irrelevant data. Additionally, this workflow allows you to take features offline that don't have a geometry - for example, features whose attributes have been populated in the office, but still need a site survey for their geometry.

How to use the sample

To modify the overrides parameters:

Use the min/max scale input fields to adjust the level IDs to be taken offline for the streets basemap.
Use the extent buffer distance input field to set the buffer radius for the streets basemap.
Check the checkboxes for the feature operational layers you want to include in the offline map.
Use the min hydrant flow rate input field to only download features with a flow rate higher than this value.
Select the "Water Pipes" checkbox if you want to crop the water pipe features to the extent of the map.

After you have set up the overrides to your liking, tap the "Generate offline map" button to start the download. A progress bar will display. Tap the "Cancel" button if you want to stop the download. When the download is complete, the view will display the offline map. Pan around to see that it is cropped to the download area's extent.

How it works

Load a web map from a PortalItem.
Create an OfflineMapTask with the map.
Generate default task parameters using the extent area you want to download with offlineMapTask.createDefaultGenerateOfflineMapParametersAsync(extent).
Generate additional "override" parameters using the default parameters with offlineMapTask.createGenerateOfflineMapParameterOverridesAsync(parameters).
For the basemap:
- Get the parameters OfflineMapParametersKey for the basemap layer.
- Get the ExportTileCacheParameters for the basemap layer with overrides.getExportTileCacheParameters().get(basemapParamKey).
- Set the level IDs you want to download with exportTileCacheParameters.getLevelIDs().add(levelID).
- To buffer the extent, use exportTileCacheParameters.setAreaOfInterest(bufferedGeometry) where bufferedGeometry can be calculated with the GeometryEngine.
To remove operational layers from the download:
- Create a OfflineParametersKey with the operational layer.
- Get the generate geodatabase layer options using the key with List<GenerateLayerOption> layerOptions = overrides.getGenerateGeodatabaseParameters().get(key).getLayerOptions()
- Loop through each GenerateLayerOption in the the list, and remove it if the layer option's ID matches the layer's ID.
To filter the features downloaded in an operational layer:
- Get the layer options for the operational layer using the directions in step 6.
- Loop through the layer options. If the option layerID matches the layer's ID, set the filter clause with layerOption.setWhereClause(sqlQueryString) and set the query option with layerOption.setQueryOption(GenerateLayerOption.QueryOption.USE_FILTER).
To not crop a layer's features to the extent of the offline map (default is true):
- Set layerOption.setUseGeometry(false).
Create a GenerateOfflineMapJob with offlineMapTask.generateOfflineMap(parameters, downloadPath, overrides). Start the job with job.start().
When the job is done, get a reference to the offline map with job.getResult.getOfflineMap()

Relevant API

ExportTileCacheParameters
GenerateGeodatabaseParameters
GenerateLayerOption
GenerateOfflineMapJob
GenerateOfflineMapParameterOverrides
GenerateOfflineMapParameters
GenerateOfflineMapResult
OfflineMapParametersKey
OfflineMapTask

Additional information

For applications where you just need to take all layers offline, use the standard workflow (using only GenerateOfflineMapParameters). For a simple example of how you take a map offline, please consult the "Generate offline map" sample.

Sample Code

MainActivity.java
Use dark colors for code blocksCopy
/* 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.generateofflinemapoverrides;

import android.Manifest;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.concurrent.Job;
import com.esri.arcgisruntime.concurrent.ListenableFuture;
import com.esri.arcgisruntime.data.ServiceFeatureTable;
import com.esri.arcgisruntime.geometry.Envelope;
import com.esri.arcgisruntime.geometry.GeometryEngine;
import com.esri.arcgisruntime.geometry.Point;
import com.esri.arcgisruntime.layers.FeatureLayer;
import com.esri.arcgisruntime.layers.Layer;
import com.esri.arcgisruntime.loadable.LoadStatus;
import com.esri.arcgisruntime.mapping.ArcGISMap;
import com.esri.arcgisruntime.mapping.LayerList;
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.symbology.SimpleLineSymbol;
import com.esri.arcgisruntime.tasks.JobMessageAddedEvent;
import com.esri.arcgisruntime.tasks.JobMessageAddedListener;
import com.esri.arcgisruntime.tasks.geodatabase.GenerateGeodatabaseParameters;
import com.esri.arcgisruntime.tasks.geodatabase.GenerateLayerOption;
import com.esri.arcgisruntime.tasks.offlinemap.GenerateOfflineMapJob;
import com.esri.arcgisruntime.tasks.offlinemap.GenerateOfflineMapParameterOverrides;
import com.esri.arcgisruntime.tasks.offlinemap.GenerateOfflineMapParameters;
import com.esri.arcgisruntime.tasks.offlinemap.GenerateOfflineMapResult;
import com.esri.arcgisruntime.tasks.offlinemap.OfflineMapParametersKey;
import com.esri.arcgisruntime.tasks.offlinemap.OfflineMapTask;
import com.esri.arcgisruntime.tasks.tilecache.ExportTileCacheParameters;

import java.io.File;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.ExecutionException;

public class MainActivity extends AppCompatActivity {

  private static final String TAG = MainActivity.class.getSimpleName();

  private Button mGenerateOfflineMapOverridesButton;
  private MapView mMapView;
  private GraphicsOverlay mGraphicsOverlay;
  private Graphic mDownloadArea;
  private GenerateOfflineMapParameterOverrides mParameterOverrides;
  private GenerateOfflineMapJob mGenerateOfflineMapJob;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // access MapView from layout
    mMapView = findViewById(R.id.mapView);

    // access button to take the map offline and disable it until map is loaded
    mGenerateOfflineMapOverridesButton = findViewById(R.id.generateOfflineMapOverridesButton);
    mGenerateOfflineMapOverridesButton.setEnabled(false);

    // authentication with an API key or named user is required
    // to access basemaps and other location services
    ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY);

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

    // create a map with the portal item
    ArcGISMap map = new ArcGISMap(portalItem);

    map.addDoneLoadingListener(() -> {
      if (map.getLoadStatus() == LoadStatus.LOADED) {
        // enable offline map button only after map is loaded
        mGenerateOfflineMapOverridesButton.setEnabled(true);
      }
    });

    // set the map to the map view
    mMapView.setMap(map);

    // create a graphics overlay for the map view
    mGraphicsOverlay = new GraphicsOverlay();
    mMapView.getGraphicsOverlays().add(mGraphicsOverlay);

    // define the download area graphic
    mDownloadArea = new Graphic();
    mGraphicsOverlay.getGraphics().add(mDownloadArea);
    SimpleLineSymbol simpleLineSymbol = new SimpleLineSymbol(SimpleLineSymbol.Style.SOLID, Color.RED, 2);
    mDownloadArea.setSymbol(simpleLineSymbol);

    // update the download area box whenever the viewpoint changes
    mMapView.addViewpointChangedListener(viewpointChangedEvent -> {
      if (map.getLoadStatus() == LoadStatus.LOADED) {
        mDownloadArea.setGeometry(createDownloadAreaGeometry());
      }
    });

    // when the button is clicked, start the offline map task job
    mGenerateOfflineMapOverridesButton.setOnClickListener(v -> showParametersDialog());
  }

  /**
   * Create an envelope representing the download area, used to define an area of interest
   *
   * @return download area Envelope
   */
  private Envelope createDownloadAreaGeometry() {
    // upper left corner of the area to take offline
    android.graphics.Point minScreenPoint = new android.graphics.Point(200, 200);
    // lower right corner of the downloaded area
    android.graphics.Point maxScreenPoint = new android.graphics.Point(mMapView.getWidth() - 200,
        mMapView.getHeight() - 200);
    // convert screen points to map points
    Point minPoint = mMapView.screenToLocation(minScreenPoint);
    Point maxPoint = mMapView.screenToLocation(maxScreenPoint);
    // use the points to define and return an envelope
    if (minPoint != null && maxPoint != null) {
      return new Envelope(minPoint, maxPoint);
    }
    return null;
  }

  /**
   * Creates parameters dialog and handles processing of input to generateOfflineMap(...) when Start Job button is clicked.
   */
  private void showParametersDialog() {

    View overrideParametersView = getLayoutInflater().inflate(R.layout.override_parameters_dialog, null);

    // min and max seek bars
    TextView currMinScaleTextView = overrideParametersView.findViewById(R.id.currMinScaleTextView);
    TextView currMaxScaleTextView = overrideParametersView.findViewById(R.id.currMaxScaleTextview);

    SeekBar minScaleSeekBar = buildSeekBar(overrideParametersView.findViewById(R.id.minScaleSeekBar),
        currMinScaleTextView, 22, 15);
    SeekBar maxScaleSeekBar = buildSeekBar(overrideParametersView.findViewById(R.id.maxScaleSeekBar),
        currMaxScaleTextView, 23, 20);
    minScaleSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
      @Override public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        currMinScaleTextView.setText(String.valueOf(progress));
        if (progress >= maxScaleSeekBar.getProgress()) {
          // set max to 1 more than min value (since max must always be greater than min)
          currMaxScaleTextView.setText(String.valueOf(progress + 1));
          maxScaleSeekBar.setProgress(progress + 1);
        }
      }

      @Override public void onStartTrackingTouch(SeekBar seekBar) {
      }

      @Override public void onStopTrackingTouch(SeekBar seekBar) {
      }
    });
    maxScaleSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
      @Override public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        currMaxScaleTextView.setText(String.valueOf(progress));
        if (progress <= minScaleSeekBar.getProgress()) {
          // set min to 1 less than max value (since min must always be less than max)
          currMinScaleTextView.setText(String.valueOf(progress - 1));
          minScaleSeekBar.setProgress(progress - 1);
        }
      }

      @Override public void onStartTrackingTouch(SeekBar seekBar) {
      }

      @Override public void onStopTrackingTouch(SeekBar seekBar) {
      }
    });

    // extent buffer seek bar
    SeekBar extentBufferDistanceSeekBar = buildSeekBar(
        overrideParametersView.findViewById(R.id.extentBufferDistanceSeekBar),
        overrideParametersView.findViewById(R.id.currExtentBufferDistanceTextView), 500, 300);

    // include layers checkboxes
    CheckBox systemValves = overrideParametersView.findViewById(R.id.systemValvesCheckBox);
    CheckBox serviceConnections = overrideParametersView.findViewById(R.id.serviceConnectionsCheckBox);

    // min hydrant flow rate seek bar
    SeekBar minHydrantFlowRateSeekBar = buildSeekBar(
        overrideParametersView.findViewById(R.id.minHydrantFlowRateSeekBar),
        overrideParametersView.findViewById(R.id.currMinHydrantFlowRateTextView), 2000, 500);

    // crop layer to extent checkbox
    CheckBox waterPipes = overrideParametersView.findViewById(R.id.waterPipesCheckBox);

    // setup dialog
    AlertDialog.Builder overrideParametersDialogBuilder = new AlertDialog.Builder(this);
    AlertDialog overrideParametersDialog = overrideParametersDialogBuilder.create();
    overrideParametersDialogBuilder.setView(overrideParametersView)
        .setTitle("Override Parameters")
        .setCancelable(true)
        .setNegativeButton("Cancel", (dialog, which) -> overrideParametersDialog.dismiss())
        .setPositiveButton("Start Job",
            (dialog, which) -> {
              // re-create download area geometry in case user hasn't changed the Viewpoint
              mDownloadArea.setGeometry(createDownloadAreaGeometry());
              defineParameters(minScaleSeekBar.getProgress(), maxScaleSeekBar.getProgress(),
                  extentBufferDistanceSeekBar.getProgress(), systemValves.isChecked(), serviceConnections.isChecked(),
                  minHydrantFlowRateSeekBar.getProgress(), waterPipes.isChecked());
            })
        .show();
  }

  /**
   * Use parameters from the override parameters dialog to define parameter overrides.
   *
   * @param minScale                  levelId
   * @param maxScale                  levelId
   * @param bufferDistance            around the given area of interest
   * @param includeSystemValves       whether to include System Valves layer
   * @param includeServiceConnections whether to include the Service Connections layer
   * @param flowRate                  to limit hydrants in a where clause
   * @param cropWaterPipes            whether to crop the pipes layer
   */
  private void defineParameters(int minScale, int maxScale, int bufferDistance, boolean includeSystemValves,
      boolean includeServiceConnections, int flowRate, boolean cropWaterPipes) {
    // create an offline map offlineMapTask with the map
    OfflineMapTask offlineMapTask = new OfflineMapTask(mMapView.getMap());
    // create default generate offline map parameters from the offline map task
    ListenableFuture<GenerateOfflineMapParameters> generateOfflineMapParametersFuture = offlineMapTask
        .createDefaultGenerateOfflineMapParametersAsync(mDownloadArea.getGeometry());
    generateOfflineMapParametersFuture.addDoneListener(() -> {
      try {
        final GenerateOfflineMapParameters generateOfflineMapParameters = generateOfflineMapParametersFuture.get();
        // don't let generate offline map parameters continue on errors (including canceling during authentication)
        generateOfflineMapParameters.setContinueOnErrors(false);
        // create parameter overrides for greater control
        ListenableFuture<GenerateOfflineMapParameterOverrides> parameterOverridesFuture = offlineMapTask
            .createGenerateOfflineMapParameterOverridesAsync(generateOfflineMapParameters);
        parameterOverridesFuture.addDoneListener(() -> {
          try {
            // get the parameter overrides
            mParameterOverrides = parameterOverridesFuture.get();
            // set basemap scale and area of interest
            setBasemapScaleAndAreaOfInterest(minScale, maxScale, bufferDistance);
            // exclude system valve layer
            if (!includeSystemValves) {
              excludeLayerFromDownload("System Valve");
            }
            // exclude service connection layer
            if (!includeServiceConnections) {
              excludeLayerFromDownload("Service Connection");
            }
            // crop pipes layer
            if (cropWaterPipes) {
              for (GenerateLayerOption generateLayerOption : getGenerateGeodatabaseParametersLayerOptions("Main")) {
                generateLayerOption.setUseGeometry(true);
              }
            }
            // set flow rate where clause on the hydrant layer
            for (GenerateLayerOption generateLayerOption : getGenerateGeodatabaseParametersLayerOptions("Hydrant")) {
              if (generateLayerOption.getLayerId() == getServiceLayerId(Objects
                  .requireNonNull(getFeatureLayerByName("Hydrant")))) {
                generateLayerOption.setWhereClause("FLOW >= " + flowRate);
                generateLayerOption.setQueryOption(GenerateLayerOption.QueryOption.USE_FILTER);
              }
            }
            // start a an offline map job from the task and parameters
            generateOfflineMap(offlineMapTask, generateOfflineMapParameters);
          } catch (InterruptedException | ExecutionException e) {
            String error = "Error creating parameter overrides: " + e.getCause().getMessage();
            Toast.makeText(this, error, Toast.LENGTH_LONG).show();
            Log.e(TAG, error);
          }
        });
      } catch (InterruptedException | ExecutionException e) {
        String error = "Error generating default generate offline map parameters: " + e.getCause().getMessage();
        Toast.makeText(this, error, Toast.LENGTH_LONG).show();
        Log.e(TAG, error);
      }
    });
  }

  /**
   * Use the generate offline map job to generate an offline map.
   */
  private void generateOfflineMap(OfflineMapTask offlineMapTask,
      GenerateOfflineMapParameters generateOfflineMapParameters) {
    // delete any offline map already in the cache
    String tempDirectoryPath = getCacheDir() + File.separator + "offlineMap";
    deleteDirectory(new File(tempDirectoryPath));
    // create an offline map job with the download directory path and parameters and start the job
    mGenerateOfflineMapJob = offlineMapTask
        .generateOfflineMap(generateOfflineMapParameters, tempDirectoryPath, mParameterOverrides);
    // show the job's progress in a progress dialog
    showProgressDialog(mGenerateOfflineMapJob);
    // replace the current map with the result offline map when the job finishes
    mGenerateOfflineMapJob.addJobDoneListener(() -> {
      if (mGenerateOfflineMapJob.getStatus() == Job.Status.SUCCEEDED) {
        GenerateOfflineMapResult result = mGenerateOfflineMapJob.getResult();
        mMapView.setMap(result.getOfflineMap());
        mGraphicsOverlay.getGraphics().clear();
        mGenerateOfflineMapOverridesButton.setEnabled(false);
        Toast.makeText(this, "Now displaying offline map.", Toast.LENGTH_LONG).show();
      } else {
        String error = "Error in generate offline map job: " + mGenerateOfflineMapJob.getError().getAdditionalMessage();
        Toast.makeText(this, error, Toast.LENGTH_LONG).show();
        Log.e(TAG, error);
      }
    });

    // show job messages in the log
    mGenerateOfflineMapJob.addJobMessageAddedListener(jobMessageAddedEvent -> Log.i(TAG, jobMessageAddedEvent.getMessage().getMessage()));

    // start the job
    mGenerateOfflineMapJob.start();
  }

  /**
   * Set basemap scale and area of interest using the given values
   *
   * @param minScale       levelId
   * @param maxScale       levelId
   * @param bufferDistance around the given area of interest
   */
  private void setBasemapScaleAndAreaOfInterest(int minScale, int maxScale, int bufferDistance) {
    // get the export tile cache parameters
    ExportTileCacheParameters exportTileCacheParameters = getExportTileCacheParameters(
        mMapView.getMap().getBasemap().getBaseLayers().get(0));
    // create a new sublist of LODs in the range requested by the user
    exportTileCacheParameters.getLevelIDs().clear();
    for (int i = minScale; i < maxScale; i++) {
      exportTileCacheParameters.getLevelIDs().add(i);
    }
    // set the area of interest to the original download area plus a buffer
    exportTileCacheParameters.setAreaOfInterest(GeometryEngine.buffer(mDownloadArea.getGeometry(), bufferDistance));
  }

  /**
   * Remove the layer named from the generate layer options list in the generate geodatabase parameters.
   *
   * @param layerName as a string
   */
  private void excludeLayerFromDownload(String layerName) {
    // get the named feature layer
    FeatureLayer targetLayer = getFeatureLayerByName(layerName);
    // get the layer's id
    long targetLayerId = getServiceLayerId(targetLayer);
    // get the layer's layer options
    List<GenerateLayerOption> layerOptions = getGenerateGeodatabaseParametersLayerOptions(layerName);
    // remove the target layer
    for (GenerateLayerOption layerOption : layerOptions) {
      if (layerOption.getLayerId() == targetLayerId) {
        layerOptions.remove(layerOption);
        break;
      }
    }
  }

  /**
   * Helper method to get export tile cache parameters for the given layer.
   *
   * @param layer to get parameters for
   * @return ExportTileCacheParameters for the given layer
   */
  private ExportTileCacheParameters getExportTileCacheParameters(Layer layer) {
    OfflineMapParametersKey key = new OfflineMapParametersKey(layer);
    return mParameterOverrides.getExportTileCacheParameters().get(key);
  }

  /**
   * Helper method to get generate geodatabase parameters for the given layer.
   *
   * @param layer to get parameters for
   * @return GenerateGeodatabaseParameters for the given layer
   */
  private GenerateGeodatabaseParameters getGenerateGeodatabaseParameters(Layer layer) {
    OfflineMapParametersKey key = new OfflineMapParametersKey(layer);
    return mParameterOverrides.getGenerateGeodatabaseParameters().get(key);
  }

  /**
   * Helper method to get the generate geodatabase parameters layer options for the given layer.
   *
   * @param layerName to get layer options for
   * @return list of GenerateLayerOptions
   */
  private List<GenerateLayerOption> getGenerateGeodatabaseParametersLayerOptions(String layerName) {
    // get the named feature layer
    FeatureLayer targetFeatureLayer = getFeatureLayerByName(layerName);
    // get the generate geodatabase parameters for the layer
    GenerateGeodatabaseParameters generateGeodatabaseParameters = getGenerateGeodatabaseParameters(targetFeatureLayer);
    // return the layer options
    return generateGeodatabaseParameters.getLayerOptions();
  }

  /**
   * Helper method to get the service layer id for the given feature layer
   *
   * @param featureLayer to get service id for
   * @return service layer id as a long
   */
  private long getServiceLayerId(FeatureLayer featureLayer) {
    ServiceFeatureTable serviceFeatureTable = (ServiceFeatureTable) featureLayer.getFeatureTable();
    return serviceFeatureTable.getLayerInfo().getServiceLayerId();
  }

  /**
   * Helper method to get the named feature layer from the map's operational layers.
   *
   * @param layerName as a String
   * @return the named feature layer, or null, if not found or if named layer is not a feature layer
   */
  private FeatureLayer getFeatureLayerByName(String layerName) {
    LayerList operationalLayers = mMapView.getMap().getOperationalLayers();
    for (Layer layer : operationalLayers) {
      if (layer instanceof FeatureLayer && layer.getName().equals(layerName)) {
        return (FeatureLayer) layer;
      }
    }
    return null;
  }

  /**
   * Shows a progress dialog for the given job.
   *
   * @param job to track progress from
   */
  private void showProgressDialog(Job job) {
    // create a progress dialog to show download progress
    ProgressDialog progressDialog = new ProgressDialog(this);
    progressDialog.setTitle("Generate Offline Map Job");
    progressDialog.setMessage("Taking map offline...");
    progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
    progressDialog.setIndeterminate(false);
    progressDialog.setProgress(0);
    progressDialog.setCanceledOnTouchOutside(false);
    progressDialog.setButton(DialogInterface.BUTTON_NEGATIVE, "Cancel", (dialog, which) -> job.cancelAsync());
    progressDialog.show();

    // show the job's progress with the progress dialog
    job.addProgressChangedListener(() -> progressDialog.setProgress(job.getProgress()));

    // dismiss dialog when job is done
    job.addJobDoneListener(progressDialog::dismiss);
  }

  @Override
  protected void onPause() {
    mMapView.pause();
    super.onPause();
  }

  @Override
  protected void onResume() {
    super.onResume();
    mMapView.resume();
  }

  @Override
  protected void onDestroy() {
    mMapView.dispose();
    super.onDestroy();
  }

  /**
   * Builds a seek bar and handles updating of the associated current seek bar text view.
   *
   * @param seekBar             view to build
   * @param currSeekBarTextView to be updated when the seek bar progress changes
   * @param max                 max value for the seek bar
   * @param progress            initial progress position of the seek bar
   * @return the built seek bar
   */
  private static SeekBar buildSeekBar(SeekBar seekBar, TextView currSeekBarTextView, int max, int progress) {
    seekBar.setMax(max);
    seekBar.setProgress(progress);
    currSeekBarTextView.setText(String.valueOf(seekBar.getProgress()));
    seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
      @Override public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        currSeekBarTextView.setText(String.valueOf(progress));
      }

      @Override public void onStartTrackingTouch(SeekBar seekBar) {
      }

      @Override public void onStopTrackingTouch(SeekBar seekBar) {
      }
    });
    return seekBar;
  }

  /**
   * Recursively deletes all files in the given directory.
   *
   * @param file to delete
   */
  private static void deleteDirectory(File file) {
    if (file.isDirectory())
      for (File subFile : file.listFiles()) {
        deleteDirectory(subFile);
      }
    if (!file.delete()) {
      Log.e(TAG, "Failed to delete file: " + file.getPath());
    }
  }
}