// Prepare the data source for editing
public void WillBeginTableEditing(UITableView tableView)
{
// See if the table already has a placeholder row for the "Add New" button
StatisticDefinition existingItem = _statisticDefinitions.Find(itm => itm.OnFieldName == AddNewStatFieldName);
// Return if there is already a placeholder row
if (existingItem != null)
{
return;
}
// Begin updating the table
tableView.BeginUpdates();
// Create an index path for the last row in the table
NSIndexPath lastRowIndex = NSIndexPath.FromRowSection(tableView.NumberOfRowsInSection(0), 0);
// Add the insert placeholder row at the end of table display
tableView.InsertRows(new NSIndexPath[] { lastRowIndex }, UITableViewRowAnimation.Fade);
// Create a new StatisticDefinition and add it to the underlying data
_statisticDefinitions.Add(new StatisticDefinition(AddNewStatFieldName, StatisticType.Count, ""));
// Apply the table edits
tableView.EndUpdates();
}
/// <summary>
/// Adds a statistic definition against an overlay
/// </summary>
/// <param name="overlay">The overlay</param>
/// <param name="statistic">The statistic definition</param>
public void AddOverlayStatistic
(
GraphicOverlay overlay,
StatisticDefinition statistic
)
{
Validate.IsNotNull(overlay);
Validate.IsNotNull(statistic);
var overlayId = overlay.OverlayId;
var entry = this.OverlayStatistics[overlayId];
var statisticAlreadyAdded = entry.Exists
(
s => s.ComponentId == statistic.ComponentId
);
if (statisticAlreadyAdded)
{
throw new InvalidOperationException
(
$"'{statistic.Name}' has already been added to the overlay."
);
}
else
{
entry.Add(statistic);
}
}
// Constructor that takes a picker for defining new statistics.
public ChooseStatisticOverlay(CGRect frame, nfloat transparency, UIColor color, UIPickerView statPicker) : base(frame)
{
// Store the statistics picker.
var statisticPicker = statPicker;
// Create a semi-transparent overlay with the specified background color.
BackgroundColor = color;
Alpha = transparency;
// Set the total height and width of the control set.
nfloat totalHeight = 400;
nfloat totalWidth = 320;
// Find the bottom x and y of the view.
nfloat centerX = Frame.Width / 2;
nfloat centerY = Frame.Bottom - 40;
// Find the start x and y for the control layout (aligned to the bottom of the view).
nfloat controlX = centerX - totalWidth / 2;
nfloat controlY = centerY - totalHeight;
// Toolbar with "Add" and "Done" buttons.
UIToolbar toolbar = new UIToolbar
{
BarStyle = UIBarStyle.Black,
Translucent = false
};
toolbar.SizeToFit();
// Add Button (add the new stat and don't dismiss the UI).
UIBarButtonItem addButton = new UIBarButtonItem("Add", UIBarButtonItemStyle.Done, (s, e) =>
{
// Get the selected StatisticDefinition.
StatDefinitionModel statPickerModel = statisticPicker.Model as StatDefinitionModel;
StatisticDefinition newStatDefinition = statPickerModel.SelectedStatDefinition;
if (newStatDefinition != null)
{
// Fire the OnMapInfoEntered event and provide the statistic definition.
OnStatisticDefined?.Invoke(this, newStatDefinition);
}
});
// Done Button (dismiss the UI, don't use the selected statistic).
UIBarButtonItem doneButton = new UIBarButtonItem("Done", UIBarButtonItemStyle.Plain, (s, e) => { OnCanceled.Invoke(this, null); });
// Add the buttons to the toolbar.
toolbar.SetItems(new[] { addButton, doneButton }, true);
// Define the location of the statistic picker.
controlY = controlY + 200;
statisticPicker.Frame = new CGRect(controlX, controlY, totalWidth, 200);
// Set the location for the toolbar.
controlY = controlY + 220;
toolbar.Frame = new CGRect(controlX, controlY, totalWidth, 30);
// Add the controls.
AddSubviews(toolbar, statisticPicker);
}
private async void ExecuteStatisticsQuery(object sender, EventArgs e)
{
// Remove the placeholder "Add statistic" row (if it exists)
StatisticDefinition placeholderRow = _statisticDefinitions.LastOrDefault();
if (placeholderRow != null && placeholderRow.OutputAlias == "")
{
_statisticDefinitions.Remove(placeholderRow);
}
// Verify that there is at least one statistic definition
if (_statisticDefinitions.Count() == 0)
{
ShowAlert("Statistical Query", "Please define at least one statistic for the query.");
return;
}
// Create the statistics query parameters, pass in the list of statistic definitions
StatisticsQueryParameters statQueryParams = new StatisticsQueryParameters(_statisticDefinitions);
// Specify the selected group fields (if any)
if (_groupByFields != null)
{
foreach (KeyValuePair <string, bool> groupField in _groupByFields.Where(field => field.Value == true))
{
statQueryParams.GroupByFieldNames.Add(groupField.Key);
}
}
// Specify the fields to order by (if any)
if (_orderByFields != null)
{
foreach (OrderFieldOption orderBy in _orderByFields)
{
statQueryParams.OrderByFields.Add(orderBy.OrderInfo);
}
}
// Execute the statistical query with these parameters and await the results
StatisticsQueryResult statQueryResult = await _usStatesTable.QueryStatisticsAsync(statQueryParams);
// Get results formatted as a dictionary (group names and their associated dictionary of results)
Dictionary <string, IReadOnlyDictionary <string, object> > resultsLookup = statQueryResult.ToDictionary(result => string.Join(", ", result.Group.Values), result => result.Statistics);
// Create an instance of a custom data source to display the results
StatisticQueryResultsDataSource statResultsDataSource = new StatisticQueryResultsDataSource(resultsLookup);
// Create a new table with a grouped style for displaying rows
UITableViewController statResultsTable = new UITableViewController(UITableViewStyle.Grouped);
// Set the table view data source
statResultsTable.TableView.Source = statResultsDataSource;
// Show the table view
this.NavigationController.PushViewController(statResultsTable, true);
}
// Handle supported edits to the data source (inserts and deletes).
public override void CommitEditingStyle(UITableView tableView, UITableViewCellEditingStyle editingStyle, NSIndexPath indexPath)
{
// Respond to the user's edit request: Insert a new statistic definition, or delete an existing one.
if (editingStyle == UITableViewCellEditingStyle.Insert)
{
// Create an overlay UI that lets the user choose a field and statistic type to add.
_chooseStatOverlay = new ChooseStatisticOverlay(_statPicker);
// Handle the OnStatisticDefined event to get the info entered by the user.
_chooseStatOverlay.OnStatisticDefined += (s, statDef) =>
{
// Verify the selected statistic doesn't exist in the collection (check for an alias with the same value).
StatisticDefinition existingItem = _statisticDefinitions.Find(itm => itm.OutputAlias == statDef.OutputAlias);
if (existingItem != null)
{
return;
}
// Make updates to the table (add the chosen statistic).
tableView.BeginUpdates();
// Insert a new row at the top of table display.
tableView.InsertRows(new[] { NSIndexPath.FromRowSection(0, 0) }, UITableViewRowAnimation.Fade);
// Insert the chosen statistic in the underlying collection.
_statisticDefinitions.Insert(0, statDef);
// Apply table edits.
tableView.EndUpdates();
};
// Handle when the user chooses to close the dialog.
_chooseStatOverlay.OnCanceled += (s, e) =>
{
// Remove the item input UI.
_chooseStatOverlay.Hide();
_chooseStatOverlay = null;
};
// Add the picker UI view (will display semi-transparent over the table view).
tableView.AddSubview(_chooseStatOverlay);
_chooseStatOverlay.TranslatesAutoresizingMaskIntoConstraints = false;
_chooseStatOverlay.LeadingAnchor.ConstraintEqualTo(tableView.SafeAreaLayoutGuide.LeadingAnchor).Active =
true;
_chooseStatOverlay.TrailingAnchor.ConstraintEqualTo(tableView.SafeAreaLayoutGuide.TrailingAnchor)
.Active = true;
_chooseStatOverlay.BottomAnchor.ConstraintEqualTo(tableView.SafeAreaLayoutGuide.BottomAnchor).Active = true;
}
else if (editingStyle == UITableViewCellEditingStyle.Delete)
{
// Remove the selected row from the table and the underlying collection of statistic definitions.
_statisticDefinitions.RemoveAt(indexPath.Row);
tableView.DeleteRows(new[] { indexPath }, UITableViewRowAnimation.Fade);
}
}
private async void OnExecuteStatisticsQueryClicked(object sender, EventArgs e)
{
// Create definitions for each statistic to calculate
StatisticDefinition statDefinitionAvgPop = new StatisticDefinition("POP", StatisticType.Average, "");
StatisticDefinition statDefinitionMinPop = new StatisticDefinition("POP", StatisticType.Minimum, "");
StatisticDefinition statDefinitionMaxPop = new StatisticDefinition("POP", StatisticType.Maximum, "");
StatisticDefinition statDefinitionSumPop = new StatisticDefinition("POP", StatisticType.Sum, "");
StatisticDefinition statDefinitionStdDevPop = new StatisticDefinition("POP", StatisticType.StandardDeviation, "");
StatisticDefinition statDefinitionVarPop = new StatisticDefinition("POP", StatisticType.Variance, "");
// Create a definition for count that includes an alias for the output
StatisticDefinition statDefinitionCount = new StatisticDefinition("POP", StatisticType.Count, "CityCount");
// Add the statistics definitions to a list
List <StatisticDefinition> statDefinitions = new List <StatisticDefinition>
{
statDefinitionAvgPop,
statDefinitionCount,
statDefinitionMinPop,
statDefinitionMaxPop,
statDefinitionSumPop,
statDefinitionStdDevPop,
statDefinitionVarPop
};
// Create the statistics query parameters, pass in the list of definitions
StatisticsQueryParameters statQueryParams = new StatisticsQueryParameters(statDefinitions);
// If only using features in the current extent, set up the spatial filter for the statistics query parameters
if (_onlyInExtentSwitch.Checked)
{
// Get the current extent (envelope) from the map view
Envelope currentExtent = _myMapView.GetCurrentViewpoint(ViewpointType.BoundingGeometry).TargetGeometry as Envelope;
// Set the statistics query parameters geometry with the envelope
statQueryParams.Geometry = currentExtent;
// Set the spatial relationship to Intersects (which is the default)
statQueryParams.SpatialRelationship = SpatialRelationship.Intersects;
}
// If only evaluating the largest cities (over 5 million in population), set up an attribute filter
if (_onlyBigCitiesSwitch.Checked)
{
// Set a where clause to get the largest cities (could also use "POP_CLASS = '5,000,000 and greater'")
statQueryParams.WhereClause = "POP_RANK = 1";
}
// Execute the statistical query with these parameters and await the results
StatisticsQueryResult statQueryResult = await _worldCitiesTable.QueryStatisticsAsync(statQueryParams);
// Display results in a list in a dialog
List <KeyValuePair <string, object> > statsList = statQueryResult.First().Statistics.ToList();
ShowStatsList(statsList);
}
// Handle supported edits to the data source (inserts and deletes)
public override void CommitEditingStyle(UITableView tableView, UITableViewCellEditingStyle editingStyle, NSIndexPath indexPath)
{
// Respond to the user's edit request: Insert a new statistic definition, or delete an existing one
if (editingStyle == UITableViewCellEditingStyle.Insert)
{
// Get the bounds of the table
CGRect ovBounds = tableView.Bounds;
ovBounds.Height = ovBounds.Height + 60;
// Create an overlay UI that lets the user choose a field and statistic type to add
_chooseStatOverlay = new ChooseStatisticOverlay(ovBounds, 0.70f, UIColor.White, _statPicker);
// Handle the OnStatisticDefined event to get the info entered by the user
_chooseStatOverlay.OnStatisticDefined += (s, statDef) =>
{
// Verify the selected statistic doesn't exist in the collection (check for an alias with the same value)
StatisticDefinition existingItem = _statisticDefinitions.Find(itm => itm.OutputAlias == statDef.OutputAlias);
if (existingItem != null)
{
return;
}
// Make updates to the table (add the chosen statistic)
tableView.BeginUpdates();
// Insert a new row at the top of table display
tableView.InsertRows(new NSIndexPath[] { NSIndexPath.FromRowSection(0, 0) }, UITableViewRowAnimation.Fade);
// Insert the chosen statistic in the underlying collection
_statisticDefinitions.Insert(0, statDef);
// Apply table edits
tableView.EndUpdates();
};
// Handle when the user chooses to close the dialog
_chooseStatOverlay.OnCanceled += (s, e) =>
{
// Remove the item input UI
_chooseStatOverlay.Hide();
_chooseStatOverlay = null;
};
// Add the picker UI view (will display semi-transparent over the table view)
tableView.Add(_chooseStatOverlay);
}
else if (editingStyle == UITableViewCellEditingStyle.Delete)
{
// Remove the selected row from the table and the underlying collection of statistic definitions
_statisticDefinitions.RemoveAt(indexPath.Row);
tableView.DeleteRows(new NSIndexPath[] { indexPath }, UITableViewRowAnimation.Fade);
}
}
// Remove the selected statistic definition from the list
private void RemoveStatisticClicked(object sender, RoutedEventArgs e)
{
// Verify that there is a selected statistic definition
if (StatFieldsListBox.SelectedItem == null)
{
return;
}
// Get the selected statistic definition and remove it from the collection
StatisticDefinition selectedStat = StatFieldsListBox.SelectedItem as StatisticDefinition;
_statDefinitions.Remove(selectedStat);
}
// Handle the selection event for the picker to create a statistic definition with the values chosen
public override void Selected(UIPickerView pickerView, nint row, nint component)
{
// Get the field name
string onFieldName = _fieldNames[pickerView.SelectedRowInComponent(0)];
// Get the statistic type
StatisticType statType = (StatisticType)_statTypes.GetValue(pickerView.SelectedRowInComponent(1));
// Create an output field alias by concatenating the field name and statistic type
string outAlias = onFieldName + "_" + statType.ToString();
// Create a new statistic definition (available from the SelectedStatDefinition public property)
_selectedStatDefinition = new StatisticDefinition(onFieldName, statType, outAlias);
}
// Handler for the AddStatisticDefinitionButton click event
private void AddStatisticDefinition(object sender, EventArgs e)
{
// Get the selected field name in the dialog
string fieldName = _fieldSpinner.SelectedItem.ToString();
// Get the selected statistic type name in the dialog and get the corresponding enum value
string statTypeName = _statSpinner.SelectedItem.ToString();
StatisticType statType = (StatisticType)Enum.Parse(typeof(StatisticType), statTypeName);
// Build a field alias for the statistic results that use the field name and statistic type
string alias = fieldName + "_" + statTypeName;
// Create a new StatisticDefinition with the field name, statistic type, and output field alias
StatisticDefinition statisticDefinition = new StatisticDefinition(fieldName, statType, alias);
// Call a function in the custom list adapter that will add the new statistic definition (and update the data in the list view)
((StatDefinitionListAdapter)_statDefListView.Adapter).AddStatisticDefinition(statisticDefinition);
}
// Constructor that takes a picker for defining new statistics.
public ChooseStatisticOverlay(UIPickerView statPicker)
{
this.TranslatesAutoresizingMaskIntoConstraints = false;
// Toolbar with "Add" and "Done" buttons.
UIToolbar toolbar = new UIToolbar();
toolbar.TranslatesAutoresizingMaskIntoConstraints = false;
statPicker.TranslatesAutoresizingMaskIntoConstraints = false;
// Add Button (add the new stat and don't dismiss the UI).
UIBarButtonItem addButton = new UIBarButtonItem("Add", UIBarButtonItemStyle.Plain, (s, e) =>
{
// Get the selected StatisticDefinition.
StatDefinitionModel statPickerModel = (StatDefinitionModel)statPicker.Model;
StatisticDefinition newStatDefinition = statPickerModel.SelectedStatDefinition;
if (newStatDefinition != null)
{
// Fire the OnMapInfoEntered event and provide the statistic definition.
OnStatisticDefined?.Invoke(this, newStatDefinition);
}
});
// Done Button (dismiss the UI, don't use the selected statistic).
UIBarButtonItem doneButton = new UIBarButtonItem("Done", UIBarButtonItemStyle.Done,
(s, e) => { OnCanceled?.Invoke(this, null); });
// Add the buttons to the toolbar.
toolbar.Items = new[] { addButton, doneButton };
statPicker.BackgroundColor = UIColor.White;
// Add the controls.
AddSubviews(toolbar, statPicker);
toolbar.BottomAnchor.ConstraintEqualTo(BottomAnchor).Active = true;
toolbar.LeadingAnchor.ConstraintEqualTo(LeadingAnchor).Active = true;
toolbar.TrailingAnchor.ConstraintEqualTo(TrailingAnchor).Active = true;
statPicker.TopAnchor.ConstraintEqualTo(TopAnchor).Active = true;
statPicker.LeadingAnchor.ConstraintEqualTo(LeadingAnchor).Active = true;
statPicker.TrailingAnchor.ConstraintEqualTo(TrailingAnchor).Active = true;
statPicker.BottomAnchor.ConstraintEqualTo(toolbar.TopAnchor).Active = true;
}
// This is called each time a cell needs to be created in the table
public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
{
// Create a new cell with a main and detail label style
UITableViewCell cell = new UITableViewCell(UITableViewCellStyle.Subtitle, null);
// Get the corresponding StatisticDefinition for this row
StatisticDefinition definition = _statisticDefinitions[indexPath.Row] as StatisticDefinition;
// Set the cell text with the field name
cell.TextLabel.Text = definition.OnFieldName;
// If this is not the placeholder (insert) row, set the detail text with the statistic type
if (definition.OnFieldName != AddNewStatFieldName)
{
cell.DetailTextLabel.Text = definition.StatisticType.ToString();
}
// Return the new cell
return(cell);
}
/// <summary>
/// Removes a statistic definition for an overlay
/// </summary>
/// <param name="overlay">The overlay</param>
/// <param name="statistic">The statistic definition</param>
public void RemoveOverlayStatistic
(
GraphicOverlay overlay,
StatisticDefinition statistic
)
{
Validate.IsNotNull(overlay);
Validate.IsNotNull(statistic);
var overlayId = overlay.OverlayId;
var entryFound = this.OverlayStatistics.ContainsKey
(
overlayId
);
if (false == entryFound)
{
throw new KeyNotFoundException
(
"The overlay specified was not found."
);
}
else
{
var entry = this.OverlayStatistics[overlayId];
if (false == entry.Contains(statistic))
{
throw new InvalidOperationException
(
$"'{statistic.Name}' has not been added to the overlay."
);
}
else
{
entry.Remove(statistic);
}
}
}
// Create a statistic definition and add it to the collection based on the user selection in the combo boxes
private void AddStatisticClicked(object sender, RoutedEventArgs e)
{
// Verify that a field name and statistic type has been selected
if (FieldsComboBox.SelectedValue == null || StatTypeComboBox.SelectedValue == null)
{
return;
}
// Get the chosen field name and statistic type from the combo boxes
string fieldName = FieldsComboBox.SelectedValue.ToString();
StatisticType statType = (StatisticType)StatTypeComboBox.SelectedValue;
// Check if this statistic definition has already be created (same field name and statistic type)
StatisticDefinition existingStatDefinition = _statDefinitions.FirstOrDefault(def => def.OnFieldName == fieldName && def.StatisticType == statType);
// If it doesn't exist, create it and add it to the collection (use the field name and statistic type to build the output alias)
if (existingStatDefinition == null)
{
StatisticDefinition statDefinition = new StatisticDefinition(fieldName, statType, fieldName + "_" + statType.ToString());
_statDefinitions.Add(statDefinition);
}
}
private async void OnExecuteStatisticsQueryClicked(object sender, EventArgs e)
{
// Create definitions for each statistic to calculate
StatisticDefinition statDefinitionAvgPop = new StatisticDefinition("POP", StatisticType.Average, "");
StatisticDefinition statDefinitionMinPop = new StatisticDefinition("POP", StatisticType.Minimum, "");
StatisticDefinition statDefinitionMaxPop = new StatisticDefinition("POP", StatisticType.Maximum, "");
StatisticDefinition statDefinitionSumPop = new StatisticDefinition("POP", StatisticType.Sum, "");
StatisticDefinition statDefinitionStdDevPop = new StatisticDefinition("POP", StatisticType.StandardDeviation, "");
StatisticDefinition statDefinitionVarPop = new StatisticDefinition("POP", StatisticType.Variance, "");
// Create a definition for count that includes an alias for the output
StatisticDefinition statDefinitionCount = new StatisticDefinition("POP", StatisticType.Count, "CityCount");
// Add the statistics definitions to a list
List <StatisticDefinition> statDefinitions = new List <StatisticDefinition>
{
statDefinitionAvgPop,
statDefinitionCount,
statDefinitionMinPop,
statDefinitionMaxPop,
statDefinitionSumPop,
statDefinitionStdDevPop,
statDefinitionVarPop
};
// Create the statistics query parameters, pass in the list of definitions
StatisticsQueryParameters statQueryParams = new StatisticsQueryParameters(statDefinitions);
// If only using features in the current extent, set up the spatial filter for the statistics query parameters
if (_onlyInExtentSwitch.On)
{
// Get the current extent (envelope) from the map view
Envelope currentExtent = _myMapView.GetCurrentViewpoint(ViewpointType.BoundingGeometry).TargetGeometry as Envelope;
// Set the statistics query parameters geometry with the envelope
statQueryParams.Geometry = currentExtent;
// Set the spatial relationship to Intersects (which is the default)
statQueryParams.SpatialRelationship = SpatialRelationship.Intersects;
}
// If only evaluating the largest cities (over 5 million in population), set up an attribute filter
if (_onlyBigCitiesSwitch.On)
{
// Set a where clause to get the largest cities (could also use "POP_CLASS = '5,000,000 and greater'")
statQueryParams.WhereClause = "POP_RANK = 1";
}
// Execute the statistical query with these parameters and await the results
StatisticsQueryResult statQueryResult = await _worldCitiesTable.QueryStatisticsAsync(statQueryParams);
// Get the first (only) StatisticRecord in the results
StatisticRecord record = statQueryResult.FirstOrDefault();
// Make sure a record was returned
if (record == null || record.Statistics.Count == 0)
{
// Notify the user that no results were returned
UIAlertView alert = new UIAlertView();
alert.Message = "No results were returned";
alert.Title = "Statistical Query";
alert.Show();
return;
}
// Display results
IReadOnlyDictionary <string, object> statistics = record.Statistics;
ShowStatsList(statistics);
}
private async void OnExecuteStatisticsQueryClicked(object sender, EventArgs e)
{
// Create definitions for each statistic to calculate
StatisticDefinition statDefinitionAvgPop = new StatisticDefinition("POP", StatisticType.Average, "");
StatisticDefinition statDefinitionMinPop = new StatisticDefinition("POP", StatisticType.Minimum, "");
StatisticDefinition statDefinitionMaxPop = new StatisticDefinition("POP", StatisticType.Maximum, "");
StatisticDefinition statDefinitionSumPop = new StatisticDefinition("POP", StatisticType.Sum, "");
StatisticDefinition statDefinitionStdDevPop = new StatisticDefinition("POP", StatisticType.StandardDeviation, "");
StatisticDefinition statDefinitionVarPop = new StatisticDefinition("POP", StatisticType.Variance, "");
// Create a definition for count that includes an alias for the output
StatisticDefinition statDefinitionCount = new StatisticDefinition("POP", StatisticType.Count, "CityCount");
// Add the statistics definitions to a list
List <StatisticDefinition> statDefinitions = new List <StatisticDefinition>
{
statDefinitionAvgPop,
statDefinitionCount,
statDefinitionMinPop,
statDefinitionMaxPop,
statDefinitionSumPop,
statDefinitionStdDevPop,
statDefinitionVarPop
};
// Create the statistics query parameters, pass in the list of definitions
StatisticsQueryParameters statQueryParams = new StatisticsQueryParameters(statDefinitions);
// If only using features in the current extent, set up the spatial filter for the statistics query parameters
if (OnlyInExtentSwitch.IsToggled)
{
// Get the current extent (envelope) from the map view
Envelope currentExtent = MyMapView.GetCurrentViewpoint(ViewpointType.BoundingGeometry).TargetGeometry as Envelope;
// Set the statistics query parameters geometry with the envelope
statQueryParams.Geometry = currentExtent;
// Set the spatial relationship to Intersects (which is the default)
statQueryParams.SpatialRelationship = SpatialRelationship.Intersects;
}
// If only evaluating the largest cities (over 5 million in population), set up an attribute filter
if (OnlyBigCitiesSwitch.IsToggled)
{
// Set a where clause to get the largest cities (could also use "POP_CLASS = '5,000,000 and greater'")
statQueryParams.WhereClause = "POP_RANK = 1";
}
try
{
// Execute the statistical query with these parameters and await the results
StatisticsQueryResult statQueryResult = await _worldCitiesTable.QueryStatisticsAsync(statQueryParams);
// Display results in the list box
StatResultsList.ItemsSource = statQueryResult.First().Statistics.Select(m => $"{m.Key}:{m.Value}").ToList();
ResultsGrid.IsVisible = true;
}
catch (Exception ex)
{
await Application.Current.MainPage.DisplayAlert("Error", ex.Message, "OK");
}
}
private async void QueryStatistics(bool onlyInExtent, bool onlyLargePop)
{
// Create definitions for each statistic to calculate.
StatisticDefinition statDefinitionAvgPop = new StatisticDefinition("POP", StatisticType.Average, "");
StatisticDefinition statDefinitionMinPop = new StatisticDefinition("POP", StatisticType.Minimum, "");
StatisticDefinition statDefinitionMaxPop = new StatisticDefinition("POP", StatisticType.Maximum, "");
StatisticDefinition statDefinitionSumPop = new StatisticDefinition("POP", StatisticType.Sum, "");
StatisticDefinition statDefinitionStdDevPop = new StatisticDefinition("POP", StatisticType.StandardDeviation, "");
StatisticDefinition statDefinitionVarPop = new StatisticDefinition("POP", StatisticType.Variance, "");
// Create a definition for count that includes an alias for the output.
StatisticDefinition statDefinitionCount = new StatisticDefinition("POP", StatisticType.Count, "CityCount");
// Add the statistics definitions to a list.
List <StatisticDefinition> statDefinitions = new List <StatisticDefinition>
{
statDefinitionAvgPop,
statDefinitionCount,
statDefinitionMinPop,
statDefinitionMaxPop,
statDefinitionSumPop,
statDefinitionStdDevPop,
statDefinitionVarPop
};
// Create the statistics query parameters, pass in the list of definitions.
StatisticsQueryParameters statQueryParams = new StatisticsQueryParameters(statDefinitions);
// If only using features in the current extent, set up the spatial filter for the statistics query parameters.
if (onlyInExtent)
{
// Get the current extent (envelope) from the map view.
Envelope currentExtent = _myMapView.GetCurrentViewpoint(ViewpointType.BoundingGeometry).TargetGeometry as Envelope;
// Set the statistics query parameters geometry with the current extent.
statQueryParams.Geometry = currentExtent;
// Set the spatial relationship to Intersects (which is the default).
statQueryParams.SpatialRelationship = SpatialRelationship.Intersects;
}
// If only evaluating the largest cities (over 5 million in population), set up an attribute filter.
if (onlyLargePop)
{
// Set a where clause to get the largest cities (could also use "POP_CLASS = '5,000,000 and greater'").
statQueryParams.WhereClause = "POP_RANK = 1";
}
try
{
// Execute the statistical query with these parameters and await the results.
StatisticsQueryResult statQueryResult = await _worldCitiesTable.QueryStatisticsAsync(statQueryParams);
// Get the first (only) StatisticRecord in the results.
StatisticRecord record = statQueryResult.FirstOrDefault();
// Make sure a record was returned.
if (record == null || record.Statistics.Count == 0)
{
ShowMessage("No result", "No results were returned.");
return;
}
// Display results.
ShowStatsList(record.Statistics);
}
catch (ArcGISWebException exception)
{
ShowMessage("There was a problem running the query.", exception.ToString());
}
}
