Implement an Activity that Calculates a Logarithm

Implementing a custom activity allows you to build a reusable, completely custom behavior to augment the existing activities that come with Geocortex Workflow.

In this article, you will learn how to create a custom activity that calculates the logarithm of a number with a given base.

Prerequisites

important

Extending Geocortex Workflow for Mobile requires development and deployment of a custom Geocortex Mobile Application using the Geocortex Mobile SDK

Follow the instructions in the Geocortex Mobile SDK page to set up the environment for extending Workflow for Geocortex Mobile.

note

A working knowledge of C# and .NET Standard is recommended before extending Workflow for Geocortex Mobile

Set up the Activity Skeleton

  1. Create a new file CalculateLog.cs in the platform agnostic project of the Geocortex Mobile Quickstart.
  2. Add a new skeleton workflow activity that implements IActivityHandler.
App1/App1/CalculateLog.cs
using App1.Workflow;
using VertiGIS.Mobile.Composition;
using Geocortex.Workflow.Runtime;
using System.Collections.Generic;
using System.Threading.Tasks;
[assembly: Export(typeof(CalculateLog))]
namespace App1.Workflow
{
public class CalculateLog : IActivityHandler
{
public static string Action { get; } = "your:unique:namespace::CalculateLog";
public Task<IDictionary<string, object>> Execute(IDictionary<string, object> inputs, IActivityContext context)
{
return Task.FromResult((IDictionary<string, object>)new Dictionary<string, object>());
}
}
}

Register the Activity with the IActivityHandlerFactory

  1. Create a new file, ActivityLoader.cs in the platform agnostic project of the Geocortex Mobile Quickstart.
  2. Implement the IActivityHandlerFactory interface and register the activity skeleton we created in the constructor.
note

Learn more about activity registration in the activity reference.

App1/App1/ActivityLoader.cs
using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using VertiGIS.Mobile.Composition;
using Geocortex.Workflow.Runtime;
using Geocortex.Workflow.Runtime.Definition;
using Geocortex.Workflow.Runtime.Execution;
using App1.Workflow;
[assembly: Export(typeof(ActivityLoader), SingleInstance = true, AsImplementedInterfaces = true)]
namespace App1.Workflow
{
public class ActivityLoader : IActivityHandlerFactory
{
/// <summary>
/// Gets a mapping of action names to implementations of <see cref="IActivityHandler"/>s.
/// </summary>
private Dictionary<string, Func<IActivityHandler>> RegisteredActivities { get; } = new Dictionary<string, Func<IActivityHandler>>();
public ActivityLoader(Func<CalculateLog> calculateLogFactory)
{
RegisteredActivities[CalculateLog.Action] = calculateLogFactory;
}
/// <summary>
/// Creates an <see cref="IActivityHandler"/>.
/// </summary>
/// <param name="action">The name of the action to create.</param>
/// <param name="token">The cancellation token.</param>
/// <param name="inspector">The <see cref="ProgramInspector"/> for the program.</param>
/// <returns>The activity handler for the given action.</returns>
public Task<IActivityHandler> Create(string action, CancellationToken token, ProgramInspector inspector = null)
{
if (action == null || token.IsCancellationRequested)
{
return Task.FromResult<IActivityHandler>(null);
}
if (RegisteredActivities.TryGetValue(action, out Func<IActivityHandler> handlerType))
{
return Task.FromResult(handlerType());
}
else
{
return Task.FromResult<IActivityHandler>(null);
}
}
}
}

Implement the Custom Activity

We now have a empty activity that Geocortex Mobile can use that takes no inputs and produces no outputs. By changing the inputs, outputs, and execute logic, you can create your own custom activity that calculates the logarithm of a number.

First, let's change the execute logic to parse inputs that make sense for a logarithm activity.

App1/App1/CalculateLog.cs
using App1.Workflow;
using VertiGIS.Mobile.Composition;
using Geocortex.Workflow.Runtime;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
[assembly: Export(typeof(CalculateLog))]
namespace App1.Workflow
{
public class CalculateLog : IActivityHandler
{
public const string Action = "your:unique:namespace::CalculateLog";
public Task<IDictionary<string, object>> Execute(IDictionary<string, object> inputs, IActivityContext context)
{
double? logBase = null;
if (inputs.ContainsKey("base"))
{
logBase = inputs["base"] as double?;
}
var value = (double)inputs["value"];
return Task.FromResult((IDictionary<string, object>)new Dictionary<string, object>());
}
}
}

Next, modify the Execute method of the activity to calculate the logarithm of a number given an optional base

App1/App1/CalculateLog.cs
using App1.Workflow;
using VertiGIS.Mobile.Composition;
using Geocortex.Workflow.Runtime;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
[assembly: Export(typeof(CalculateLog))]
namespace App1.Workflow
{
public class CalculateLog : IActivityHandler
{
public const string Action = "your:unique:namespace::CalculateLog";
public Task<IDictionary<string, object>> Execute(IDictionary<string, object> inputs, IActivityContext context)
{
double? logBase = null;
if (inputs.ContainsKey("base"))
{
logBase = inputs["base"] as double?;
}
var value = (double)inputs["value"];
double logResult;
if (logBase != null)
{
logResult = Math.Log(value, (double)logBase);
}
else
{
logResult = Math.Log(value);
}
return Task.FromResult((IDictionary<string, object>)new Dictionary<string, object>()
{
["result"] = logResult
});
}
}
}

Test your Activity

Now you can build a workflow for Geocortex Mobile that uses your new activity!

tip

If you want your custom activity to show up with a friendly user interface in Geocortex Workflow Designer, check out Registering .NET Activities with Geocortex Workflow Designer.

The RunActivity activity can be used to execute your activity by the name defined in CalculateLog.cs (for this example, your:unique:namespace::CalculateLog).

Next you need to run the workflow you just created in your Geocortex Mobile SDK project.

You can do this by configuring the layout and app config to run a workflow. You will need to copy the ID of the the workflow you created into the app.json


App1/App1/app.json
{
"schemaVersion": "1.0",
"items": [
{
"$type": "layout",
"id": "desktop-layout",
"url": "resource://layout-large.xml",
"tags": ["large"]
},
{
"$type": "workflow",
"id": "custom-workflow",
"title": "Custom Workflow",
"target": "#taskbar",
"portalItem": "<your-workflow-id>"
},
{
"$type": "menu",
"id": "iwtm",
"items": [
{
"title": "Run Custom Workflow",
"isEnabled": true,
"iconId": "workflow",
"action": {
"name": "workflow.run",
"arguments": {
"id": "custom-workflow"
}
}
}
]
}
]
}

Relevant SDK Sample

Check out the relevant Geocortex Mobile SDK Sample:

Next Steps

Now you know how to build a basic Workflow activity for Geocortex Mobile. Next, you can learn how to access app properties in an activity, build custom form elements, use the ArcGIS Runtime SDK for .NET in your activities and more.

Implement a Custom Form Element

Implement a custom form element for applications like Geocortex Mobile

Add a Callout to the Map through a Custom Activity

Access the map in custom activities for Geocortex Mobile

Use the ArcGIS Runtime SDK for .NET in an activity.

Use the ArcGIS Runtime SDK for .NET in an activity or form element

Reference other Third Party Libraries

Reference other third party libraries in your activities and form elements